SPEAKERS CONTENTS INSERTS
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81–931PS
2003
THE THREAT OF NEAR-EARTH ASTEROIDS
HEARING
BEFORE THE
SUBCOMMITTEE ON SPACE AND AERONAUTICS
COMMITTEE ON SCIENCE
HOUSE OF REPRESENTATIVES
ONE HUNDRED SEVENTH CONGRESS
SECOND SESSION
OCTOBER 3, 2002
Serial No. 107–89
Printed for the use of the Committee on Science
Available via the World Wide Web: http://www.house.gov/science
COMMITTEE ON SCIENCE
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HON. SHERWOOD L. BOEHLERT, New York, Chairman
LAMAR S. SMITH, Texas
CONSTANCE A. MORELLA, Maryland
CHRISTOPHER SHAYS, Connecticut
CURT WELDON, Pennsylvania
DANA ROHRABACHER, California
JOE BARTON, Texas
KEN CALVERT, California
NICK SMITH, Michigan
ROSCOE G. BARTLETT, Maryland
VERNON J. EHLERS, Michigan
DAVE WELDON, Florida
GIL GUTKNECHT, Minnesota
CHRIS CANNON, Utah
GEORGE R. NETHERCUTT, JR., Washington
FRANK D. LUCAS, Oklahoma
GARY G. MILLER, California
JUDY BIGGERT, Illinois
WAYNE T. GILCHREST, Maryland
W. TODD AKIN, Missouri
TIMOTHY V. JOHNSON, Illinois
MIKE PENCE, Indiana
FELIX J. GRUCCI, JR., New York
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MELISSA A. HART, Pennsylvania
J. RANDY FORBES, Virginia
RALPH M. HALL, Texas
BART GORDON, Tennessee
JERRY F. COSTELLO, Illinois
JAMES A. BARCIA, Michigan
EDDIE BERNICE JOHNSON, Texas
LYNN C. WOOLSEY, California
LYNN N. RIVERS, Michigan
ZOE LOFGREN, California
SHEILA JACKSON LEE, Texas
BOB ETHERIDGE, North Carolina
NICK LAMPSON, Texas
JOHN B. LARSON, Connecticut
MARK UDALL, Colorado
DAVID WU, Oregon
ANTHONY D. WEINER, New York
BRIAN BAIRD, Washington
JOSEPH M. HOEFFEL, Pennsylvania
JOE BACA, California
JIM MATHESON, Utah
STEVE ISRAEL, New York
DENNIS MOORE, Kansas
MICHAEL M. HONDA, California
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Subcommittee on Space and Aeronautics
DANA ROHRABACHER, California, Chairman
LAMAR S. SMITH, Texas
JOE BARTON, Texas
KEN CALVERT, California
ROSCOE G. BARTLETT, Maryland
DAVE WELDON, Florida
CHRIS CANNON, Utah
GEORGE R. NETHERCUTT, JR., Washington
FRANK D. LUCAS, Oklahoma
GARY G. MILLER, California
MIKE PENCE, Indiana
J. RANDY FORBES, Virginia
SHERWOOD L. BOEHLERT, New York
BART GORDON, Tennessee
NICK LAMPSON, Texas
JOHN B. LARSON, Connecticut
DENNIS MOORE, Kansas
ZOE LOFGREN, California
SHEILA JACKSON LEE, Texas
BOB ETHERIDGE, North Carolina
MARK UDALL, Colorado
DAVID WU, Oregon
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ANTHONY D. WEINER, New York
RALPH M. HALL, Texas
BILL ADKINS Subcommittee Staff Director
ED FEDDEMAN Professional Staff Member
RUBEN VAN MITCHELL Professional Staff Member
CHRIS SHANK Professional Staff Member
RICHARD OBERMANN Democratic Professional Staff Member
TOM HAMMOND Staff Assistant
C O N T E N T S
October 3, 2002
Hearing Charter
Opening Statements
Statement by Representative Dana Rohrabacher (CA–45), Chairman, Subcommittee on Space and Aeronautics, Committee on Science, U.S. House of Representatives
Written Statement
Statement by Representative Bart Gordon (TN–04), Minority Ranking Member, Subcommittee on Space and Aeronautics, Committee on Science, U.S. House of Representatives
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Witnesses
Dr. David Morrison, Senior Scientist, NASA Ames Research Center
Oral Statement
Written Statement
Biography
Dr. Edward J. Weiler, NASA Associate Administrator for Space Science
Oral Statement
Written Statement
Biography
Dr. Joseph A. Burns, Irving Porter Church Professor of Engineering and Astronomy, Cornell University
Oral Statement
Written Statement
Biography
Dr. Brian G. Marsden, Director, Minor Planet Center, Smithsonian Astrophysical Observatory
Oral Statement
Written Statement
Biography
Brigadier General Simon ''Pete'' Worden, U.S. Air Force
Oral Statement
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Written Statement
Biography
Discussion
NEO Survey
Differentiating Between NEOs and Nuclear Explosions
NEO Near-Misses
False Alarms
NASA's Role in Follow-on Research and Categorization
Rationale for NEO Programs and Spending
Air Force Capabilities Relating to NEOs
NEO Mitigation Timetables
NEO Oceanic Impact Effects
NEO Near-Misses (Cont.)
NEO Oceanic Impact Effects (Cont.)
Long-period Comets
Appendix 1: Answers to Post-Hearing Questions
Dr. David Morrison, Senior Scientist, NASA Ames Research Center
Dr. Edward J. Weiler, NASA Associate Administrator for Space Science
Dr. Joseph A. Burns, Irving Porter Church Professor of Engineering and Astronomy, Cornell University
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Dr. Brian G. Marsden, Director, Minor Planet Center, Smithsonian Astrophysical Observatory
Brigadier General Simon ''Pete'' Worden, U.S. Air Force
Appendix 2: Additional Material for the Record
Statement Submitted by William S. Smith, Jr., President, Association of Universities for Research in Astronomy, Inc.
Statement Submitted by Marc Schlather, President, ProSpace
H.R. 5303, The Charles ''Pete'' Conrad Astronomy Awards Act
THE THREAT OF NEAR-EARTH ASTEROIDS
THURSDAY, OCTOBER 3, 2002
House of Representatives,
Subcommittee on Space and Aeronautics,
Committee on Science,
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Washington, DC.
The Subcommittee met, pursuant to call, at 10:10 a.m., in Room 2318 of the Rayburn House Office Building, Hon. Dana Rohrabacher [Chairman of the Subcommittee] presiding.
HEARING CHARTER
SUBCOMMITTEE ON SPACE AND AERONAUTICS
COMMITTEE ON SCIENCE
U.S. HOUSE OF REPRESENTATIVES
The Threat of Near-Earth Asteroids
THURSDAY, OCTOBER 3, 2002
10:00 A.M.–12:00 P.M.
2318 RAYBURN HOUSE OFFICE BUILDING
1. Purpose
On Thursday, October 3, 2002, at 10:00 a.m. in room 2318 of the Rayburn House Office Building, the Subcommittee on Space and Aeronautics will hold a hearing on The Threat of Near-Earth Asteroids. The hearing will examine the status of the current national survey of asteroids and comets known as Near-Earth Objects (''NEOs''), the threat of a NEO impact, future goals for the survey, and the national policy regarding NEOs.(see footnote 1)
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Asteroids and comets with orbital distances from the sun similar to Earth's are designated as NEOs. While many of these pose no threat of collision with the Earth, a subset known as ''Earth-crossing asteroids'' (ECAs) and ''potentially hazardous asteroids'' (PHAs) have orbits with the potential for a close encounter or collision with the Earth. The Earth is bombarded by small meteorites every day, but most of these objects are less than 50 meters in size and burn up in the atmosphere. Larger objects impact the Earth less frequently but can cause enormous damage depending on their size, as described in Figure 1. For example, scientists now generally believe that the mass extinction at the end of the Cretaceous period, which included dinosaur extinction, was the result of climate and ecosystem disruption from a massive asteroid impact off the Yucatan peninsula. The fossil record includes a layer of extra-terrestrial material, churned up and distributed by the impact around the globe, at exactly this time period. More recently, the asteroid impact of 1908 in Tunguska, Siberia flattened 2000 square kilometers of forest with an impact energy 1,000 times that of the Hiroshima atomic bomb. Thus the potential for disaster by an asteroid impact has already been demonstrated in our planet's history.
The threat of hazardous Near-Earth Objects has gained greater attention in the public and press recently, in part as a response to several close encounters with asteroids discovered by the current national survey for such objects. Currently NASA is surveying large NEOs with a goal of finding and cataloging 90 percent of objects larger than one kilometer by 2008. Over 600 of these large objects have already been found (Figure 2). In addition to examining the status and results of this survey and the NEO threat, this hearing will explore the question of next steps beyond this survey goal, including the costs, benefits, and technical challenges of extending the survey to include smaller, yet still potentially very hazardous, objects. Agency roles, interagency cooperation, and the possibilities for international contributions to the NEO survey effort will be discussed.
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In particular, the important role of amateur astronomers in the NEO survey and tracking effort will be highlighted. Amateur astronomers are responsible for much of the important tracking of NEOs after they are discovered. Earlier this year, Rep. Dana Rohrabacher (R–CA) introduced the ''Pete Conrad'' bill, H.R. 5303. This bill would establish awards for U.S. amateur astronomers who contribute the most toward the discovery and tracking of Near-Earth Asteroids.
2. Major Issues
Status of the Current U.S. Survey for Near-Earth Objects. At the request of Congress in 1994, NASA initiated a plan to locate all NEOs larger than one kilometer in diameter. The resulting strategy, known as the ''Spaceguard'' goal, is to discover and catalog 90 percent of these large objects by 2008. The Near-Earth Object Program Office at the NASA Jet Propulsion Laboratory was established in 1998 to coordinate NASA efforts to discover and track these potentially hazardous NEOs. Congress recently provided $3.5M in FY 2001 and an additional $3.5M in FY 2002 for NASA's NEO survey activities. The status of the survey and likelihood of reaching the Spaceguard goal will be addressed in the hearing. Other related questions include: What survey projects are currently funded by NASA? What contributions do Air Force telescopes make to NEO survey projects?
Amateur Astronomer Contributions. Amateur astronomers play an important role in NEO monitoring. While their equipment is generally not suitable for the discovery of many new objects, these astronomers are often well suited for tracking objects already discovered, which is crucial for predicting orbital paths and detecting objects deviating from their predicted orbit. Legislation introduced by Rep. Rohrabacher (the ''Pete Conrad'' bill, H.R. 5303) will offer monetary awards through NASA to reward U.S. amateur astronomers who contribute the most toward the discovery and tracking of NEOs. The importance of contributions from amateur astronomers in both current and future NEO survey efforts will be highlighted in the hearing.
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Future Direction of National NEO Survey and Response Efforts. The question now is what to do next in the survey of, and in planning for a response to, hazardous NEOs. While the current survey is designed primarily for objects larger than one kilometer in size, most NEOs are smaller than one kilometer, and asteroids of only a few hundred meters in size could potentially destroy an entire city or country. Asteroids of this smaller size are far more likely to collide with Earth within the next century than are the kilometer-sized objects. What should be the future goal for NEO surveys? What is the cost of extending the survey down to objects of a few hundred meters in size? What is the threat of these objects relative to the cost and technical challenge of finding and monitoring them? What technologies are needed for future NEO survey work? Which agencies are best suited for the NEO survey, data management, and planning for a response to a threatening NEO? What should be the role of NASA, the Department of Defense, the National Science Foundation, and other relevant agencies in developing and executing a unified set of recommendations for protection from NEOs?
Data Management. Currently all asteroids and comets discovered around the world are reported to the Minor Planet Center (MPC) of the Smithsonian Astrophysical Observatory at Harvard University. The MPC disseminates information on new discoveries and orbit parameters internationally, making for an efficient coordinated world-wide system. However, the enormous magnitude of new data that would come from a survey of smaller NEOs may require significant increases in computing capabilities and personnel at the MPC for managing such data. Questions include the following: What would be the increased personnel, computational, and funding requirements for the increased data rate that would result from extending the survey to smaller objects? Would the MPC be able to handle the volume of data from proposed NEO survey telescopes like the Large-Aperture Synoptic Survey Telescope (NSF) and the ''Pan-Starrs'' Panoramic Optical Imager (Air Force)?
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3. Background
Recent Impacts and Near-Misses: In early January of this year (2002), an asteroid designated as 2001 YB5 passed the Earth at a distance of 510,000 miles, less than twice the distance of the Moon. It is estimated to be several hundred meters in size, which is large enough to destroy an entire country the size of England. (Asteroids of about a kilometer in size could wipe out life on the entire planet.) The asteroid was discovered only one month earlier by the NEAT (Near-Earth Asteroid Tracking) telescope at Mount Palomar. At present, nothing could have been done to avert it if the asteroid had been found to be on a collision course with the Earth. Another asteroid, 2002 EM7, passed the Earth at roughly the distance of the Moon on March 8th of this year, but was not detected until March 12th after it moved out of the Sun's glare. More recently, asteroid 2002 MN, a football-field sized object, passed by Earth at only one-third the distance to the Moon. Such discoveries are stark reminders of the possibility of impacts, but they also signify the importance of performing the NEO survey. It is expected that many of these discoveries will occur after the object has passed by the Earth. The current survey picks up some of these smaller objects, but a complete survey of such objects will require an extension of the survey goals, capabilities, and support. There are other impacts of note within the last decade. In 1994, for example, Comet Shoemaker-Levy 9 collided with Jupiter in a spectacular display.
Expert Recommendations for NEO Survey Strategies: The critical issue is that there is no current unified, cohesive federal vision and plan for future NEO surveys and responses. As a result, multiple independent proposals involving different telescopes, technologies, and agencies are under consideration (see below). If all are pursued independently, these different approaches may result in unnecessary duplication of effort. A more integrated and coordinated program may result in a more effective use of these assets. These differing ideas, discussed below, will be discussed and debated at the hearing.
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Astronomy/Solar System science: The recent National Research Council decadal survey report on solar system exploration, ''New Frontiers in the Solar System: An Integrated Exploration Strategy,'' includes extensive analyses and recommendations regarding the survey and study of Near-Earth Objects. Their primary recommendation is for NASA and the National Science Foundation to contribute equally to the construction and operation of a new ''Large-Aperture Synoptic Survey Telescope'' (LSST) to efficiently survey all NEOs down to a size of 300 meters. The LSST would be a very sensitive and efficient instrument for surveying the entire sky quickly and regularly for both small and large NEOs. The telescope would serve a dual-use function as it would also serve as an instrument for other astronomy surveys.
Military Community: Brigadier General Pete Worden, Deputy Director for Space Operations of the U.S. Strategic Command, has suggested that the U.S. military could play a greater role in future NEO strategy. At present the U.S. Air Force already contributes some search instruments to NASA-directed survey projects such as the Lincoln Near-Earth Asteroid Research Project (LINEAR) at the White Sands Missile Range in New Mexico. Worden proposes that future military surveillance systems could make a valuable contribution to the NEO survey. The Air Force is also developing the Panoramic Optical Imager (Pan Starrs) telescope facility in Hawaii that could be operational in four years and could potentially search the entire sky every few days, detecting objects nearly 100 times fainter than the best existing NEO search telescopes. However, as discussed above, the science-based LSST is also proposed as an efficient and sensitive instrument for full-sky asteroid surveys. One emerging questions is whether both telescopes (or other alternatives) are needed for NEO surveys. In either case, data from the surveys would need to be quickly accessible to the scientific community. In addition to supporting surveys, the military could possibly develop mitigation strategies should a threatening Near-Earth Object be detected. Clearly, such plans would need to be made in advance of any such discovery or close approach. General Worden also warns that NEOs that explode in the Earth's atmosphere several times every year could be mistaken for a nuclear detonation in times of international tension, triggering an unwarranted response. Data from NEO explosions detected by U.S. military surveillance systems could potentially be quickly shared with affected nations if an appropriate warning center is developed.
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NASA: Current U.S. NEO survey efforts are funded and coordinated through NASA. Such efforts include primarily the LINEAR and Near-Earth Asteroid Tracking (NEAT) projects using Air Force telescopes. The resulting survey data are handled by the Minor Planet Center of the Smithsonian Astrophysical Observatory (see below). Nearly 1800 Near-Earth Asteroids have been discovered (Figure 2). If the NEO survey is extended to comprehensively include objects smaller than one kilometer, larger telescopes and augmented data management resources will be needed. NASA would also be likely to take the lead should it be determined that a satellite-based telescope is best-suited for future NEO surveys. NASA is also best-suited for detailed studies of the composition of threatening asteroids; this is pertinent to plans for any type of mitigating response.
4. Witnesses
Dr. Edward Weiler, NASA Associate Administrator for Space Science, has been asked to address the following questions: How is NASA currently carrying out their mandate to conduct a comprehensive survey of Near-Earth Objects? What is the status of meeting the ''Spaceguard Goal'' for finding 90 percent of all NEOs larger than one kilometer by 2008? What roles can NASA best fill in future NEO activities such as surveys, scientific studies, data management, and planning for possible mitigation of a threat?
Dr. David Morrison, Senior Scientist, NASA Ames Research Center, has been asked to address the following questions: What are the hazards we face from Near-Earth Objects? How does that threat depend upon the size of the objects, and what is the likelihood of an impact that is dangerous for life on Earth? What is the justification for the current Spaceguard survey goal of finding 90 percent of objects larger than one kilometer by 2008? What are the benefits and challenges of extending the survey to comprehensively include smaller objects of a few hundred meters in size?
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Brigadier General Simon ''Pete'' Worden, U.S. Air Force, has been asked to address the following questions: What is the current role of the U.S. Air Force in surveys of Near-Earth Objects? What is your perspective on the threat NEOs present to national security? What future military surveillance systems could efficiently search the sky for NEOs? What issues, such as restrictions on data release, would need to be addressed if the U.S. Air Force were to conduct NEO surveys or to serve as a clearinghouse for such data? What could the role of the military be in planning mitigation efforts should a threatening object be discovered?
(Note: General Worden is representing his own personal views as a military leader and an expert on military surveillance and Near-Earth Objects. His views are not necessarily those of the U.S. Air Force.)
Dr. Brian Marsden, Director, Minor Planet Center, Smithsonian Astrophysical Observatory, has been asked to address the following questions: What role does the Minor Planet Center play in the NEO survey? What is the role of amateur astronomers in discovery and tracking of NEOs? How do awards such as those offered in the ''Pete Conrad'' bill (H.R. 5303) encourage amateur contributions toward NEO observations? What challenges for data management would result from the large increase in data if the NEO survey is extended to include smaller, more numerous objects?
Dr. Joseph Burns, Irving Porter Church Professor of Engineering and Astronomy, Cornell University, has been asked to address the following questions: What are the recommendations of the recent decadal survey reports from the National Academy of Sciences regarding the future of NEO surveys? Why did the Solar System Exploration decadal survey report recommend that NASA and the National Science Foundation partner equally to design, build, and operate a survey telescope such as the Large-Aperture Synoptic Survey Telescope (LSST) for surveys of NEOs? How do agency roles and cooperation impact the work of astronomers conducting the NEO survey?
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81931a.eps
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Chairman ROHRABACHER. I call to order this meeting on the Space and Aeronautics Subcommittee, and without objection, the Chair will be granted authority to recess this committee at any time. At today's hearing, we will examine a serious, potentially life-threatening, topic. And at a time when the Capital is all abuzz about Saddam Hussein and the threat, the potential threat there of Iraqis getting their hands on weapons of mass destruction, let us note that there are objects out in space that could be heading toward the Earth that contain so much destructive power as to look—make Saddam Hussein look like a benign factor in our lives. And not to say that Saddam Hussein isn't a more eminent threat as compared to an object out in space, a comet or a meteor, but today, we want to make sure that we are taking care of the long-term threats as well as the short-term threats to the people of the United States, whether it be Saddam Hussein or whether it be some asteroid or meteorite that might bash into the planet and kill millions of people. The threat posed by incoming asteroids and comets is, of course, the threat. Excuse me.
The purpose of this hearing and in this hearing, we will discuss the status of the current national survey of asteroids and comets, known as Near-Earth Objects, the threat of Near-Earth Object impacts, and the possible mitigation of those threats and how national policy should respond to the Near-Earth Object issue. In 1998, the Subcommittee held—this Subcommittee held a hearing on this very same subject, and since that time, three Earth—Near-Earth Asteroids with a potential for an encounter or a possible encounter with the Earth, at least it was a close encounter, have occurred, all within this year. We should not take comfort in the fact that these asteroids missed us, because in astronomical terms, they missed us by a hair. The issue before us today is what needs to be done to understand Near-Earth Objects and the threat that they pose, and what agency or agencies are best qualified and best suited to help us understand this threat and perhaps to thwart it.
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In 1998, NASA initiated the Spaceguard Program to survey the Near-Earth Object population of objects, and these objects that were surveyed are larger than one kilometer and those that threaten our ''Earth neighborhood.'' NASA, with its Spaceguard Program, is intended to survey 90 percent of that population by 2008. Thus far, more than 600 large asteroids have been surveyed, and NASA is to be commended for this effort. Unfortunately, NASA's annual budget for this survey is less than $4 million; thus Near-Earth Object surveying does not appear to be a very high priority at NASA. It has been suggested that the United States Air Force assets could play a role in this detection of these Near-Earth Objects. And in the absence of a coordinated national Near-Earth Object policy, the United States Government and no government agency, and nothing in our government is necessarily responsible for addressing this issue.
The reporting this year of asteroids several hundred in—several hundred meters in size or more is a constant reminder of the very real chance that these objects could hit the Earth. And I have been told that any one person's chance of being killed by an impacting asteroid is probably no greater than the chance of someone going to Las Vegas and getting the royal straight flush in a poker game. And that is what was told to us during the last hearing a couple of years ago. And I remember when whoever the one of us made that analysis, I remember saying to myself, ''Oh, my gosh, I did get a royal straight flush in Las Vegas once.'' So it is something to keep in mind. So given the number of Near-Earth Objects presumed that are—that we presume are out there, it is a matter of time before we are faced with an unparalleled event in human history. And that would be an unparalleled threat to the survival—perhaps the survival of our whole planet.
That said, we must know a great deal more about Near-Earth Objects, and my bill, H.R. 5303, the ''Charles 'Pete' Conrad Astronomy Awards Act,'' which passed just two nights ago, is intended to reward outstanding amateur astronomers that discover new and track previously identified large asteroids. It is hoped the bill will strengthen existing government capabilities for tracking natural space objects by encouraging private citizens to observe asteroids and comets, and to hopefully enlist young people in looking up into space and get them involved at a very early age and being involved with space and science. The title of the bill was chosen to honor Pete Conrad, the third man to walk on the moon, for his tremendous contributions to aerospace over these last four decades. And of course, I want to thank Mr. Worden and our—my colleagues on the other side of the aisle, on both sides of the aisle, for the support they gave to this legislation, which passed two nights ago. Pete Conrad embodied the American ''can-do'' spirit, and that is something we need to always keep, because especially if we face threats like the one we are talking about today. That ''can-do'' spirit: whatever the challenge is, we will be able to handle it.
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The question still remains what to do next so we can handle any potential threat from beyond. And what we need to do is clearly understand the future goals of the national Near-Earth Object policy in terms of what this might cost us, what technical knowledge we need to know in order to come to grips with this possible threat. We need to know what technologies need to be developed, and we need to find ways of monitoring and mitigating the Near-Earth Object threat.
So today's expert panel will discuss these critical and urgent issues and help us sort through what should be done to address this threat and just how big that threat is.
Now is—was that a vote? And what—and how much time do we have?
[No response.]
Chairman ROHRABACHER. I now recognize my Ranking Member Bart Gordon from Tennessee for his opening statement.
Mr. GORDON. Thank you, Mr. Chairman, and good morning. And welcome to our witnesses today.
This hearing on Near-Earth Asteroids is the latest in a series that stretches back over the last decade. I note that one of the witnesses, Dr. David Morrison, first testified on this topic before the Science Committee almost 10 years ago. We have come a long way since the late George Brown, former Chairman of the Science Committee, first attempted to focus attention on the potential threat posed by Near-Earth Asteroids. Much progress has been made in detecting and cataloging Near-Earth Asteroids in the last decade. And I hope that our witnesses will provide us with an update on that progress.
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Now some have argued that the search for potential hazardous asteroids should be extended to objects of smaller size, and I would like to hear the witnesses' views on the merits of such an expanded search. It also has been pointed out that there is a class of objects, namely long-period comets, that pose a potential threat to the Earth. But those objects are very difficult to detect until they are relatively near the Earth. I would like our witnesses to discuss how serious a threat those long-period comets pose and whether there is anything that can be done to improve their rate of detection.
Finally, before I yield back my time, I would like to congratulate Chairman Rohrabacher on the passage of H.R. 5303 earlier this week. Over the years, he has been a strong advocate of efforts to detect and catalogue Near-Earth Asteroids. H.R. 5303 is just his latest initiative in that regard. I commend him for his commitment, and I hope the Senate will follow the House's lead and pass H.R. 5303.
Well, again, my welcome to our witnesses. I look forward to hearing your testimony, and I yield back the balance of my time.
Chairman ROHRABACHER. Thank you very much. Let me just say that I appreciate very much that you reminded us that George Brown, Chairman of the Full Committee, was someone who started the—our interest in this area. And George Brown was—a lot of the things that we are doing now started with George Brown making sure that the technology was up there and things. There are just so many things that we can trace back to the activism that he had in the Science Committee, so I am very pleased to do that. And also, I would like to remind those in the hearing today that I have actually spoken to Senator Nelson from Florida, who used to be the Chairman of this Subcommittee. And he is seriously considering authoring the Pete Conrad bill in the Senate and getting that through there so we could actually enact it into law.
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So with that, how many more minutes do we have before——
Ms. WISEMAN. Five, five and a half.
Chairman ROHRABACHER. We have five and a half minutes before this vote, and is it a single vote?
Ms. WISEMAN. I believe.
Chairman ROHRABACHER. You believe it is just one vote? So Roscoe, do you have an opening statement for us?
Mr. BARTLETT. I am Roscoe Bartlett from Maryland. I am—in a future life, I was a scientist. I note that the evidence indicates that at one time, in the past, our world was grossly changed by an impact, and we now potentially have the capability to be forewarned of this and maybe even to do something about it. So I look forward to this hearing. Thank you very much for coming.
Chairman ROHRABACHER. Okay. We have about four minutes to go and vote. Why don't we recess for 10 minutes, and we will be back in 10 minutes?
[Recess.]
Chairman ROHRABACHER. I now call the Subcommittee to order. Again, let me apologize for what is going on here with the Chair. I am also a Member of the International Relations Committee, and we are marking up the Iraqi resolution, as we speak. And of course, this effort today is something that I have been long-interested in, and so here I am after a couple of years of trying to have this hearing. I have to go back and forth. For those people who don't know how Washington works and who want to understand that out in the Hinterland, this is what happens half of the time, does it not, Bart, where two of the most important things that you are thinking about for a full year come to fruition at exactly the same moment. And so the same way with asteroids, okay, coming at exactly at that moment. Okay.
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Now we have heard our opening statements, and without objection, the opening statements of all the Members will be put into the written record so we can have the testimony as soon as possible. And hearing no objections, so ordered.
[The prepared statement of Mr. Rohrabacher follows:]
PREPARED STATEMENT OF CHAIRMAN DANA ROHRABACHER
Today's hearing will examine a serious, potentially life-threatening topic, the threat posed by incoming asteroids and comets. In this hearing, we will discuss the status of the current national survey of asteroids and comets known as Near-Earth Objects (NEOs), the threat of NEO impacts, possible mitigation of those threats, and how national policy should respond to the NEO issue. In 1998, the Subcommittee held a hearing on this same subject. Since that time, three near-Earth asteroids with the potential for a close encounter with the Earth have occurred—all within this year. We should not take comfort in the fact that these asteroids missed us, because in astronomical terms they missed us by a hair. The issue before us today is what needs to be done to understand the NEO threat and what agency or agencies are best suited to do it.
In 1998, NASA initiated the Spaceguard Program to survey the NEO population of objects larger than one kilometer that threaten our ''Earth neighborhood.'' NASA with its Spaceguard Program is intended to survey 90 percent of that population by 2008. Thus far, more than 600 large asteroids have been surveyed, and NASA is to be commended for this effort. Unfortunately, NASA's annual budget for NEO surveys is less then $4 million. Thus, NEO surveying does not appear to be a high priority at NASA. It has been suggested that U.S. Air Force assets could play a role in NEO detection. In the absence of a coordinated national NEO policy, however, no U.S. Government agency is responsible for addressing the NEO issue.
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The reporting this year of asteroids several hundred meters in size are constant reminders of the very real chance of these objects impacting the Earth. I have been told your chance of being killed by an impacting asteroid is greater than the chance of getting a Royal Flush in a Poker game. Well, I got a Royal Flush. Given the number of NEOs presumed out there, it's a matter of time before we're faced with an event unparalleled in human history.
That said, we must know a great deal more about NEOs. My bill H.R. 5303, the ''Charles 'Pete' Conrad Astronomy Awards Act,'' is intended to reward outstanding amateur astronomers that discover new and track previously identified large asteroids. It is hoped the bill will strengthen existing government capabilities for tracking natural space objects by encouraging private citizens to observe asteroids and comets. The title is chosen to honor Pete Conrad, the third man to walk on the Moon, for his tremendous contributions to the aerospace field over the last four decades. He embodies the American ''can-do'' spirit we all strive for.
The question still remains what to do next beyond the current NEO surveys. We need to clearly understand the future goals of a national NEO policy in terms of cost, technical know-how, and technology to meet the challenge of finding, monitoring, and mitigating NEOs. Today's expert panel will discuss these critical and urgent issues and help us sort through what should be done to address the threats NEOs pose.
Chairman ROHRABACHER. I also ask unanimous consent to insert, at the appropriate place in the record, the background memorandum prepared by the majority staff for this hearing. And hearing no objection, so ordered.
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And given the importance of today's topic, we have asked other experts to submit written statements in order to build a strong public record on this subject. So I would ask unanimous consent to place any additional written material that we receive into the hearing record. Hearing no objection. So before I introduce our witnesses, let me suggest that if you could summarize your statements to about five minutes, it would be very helpful to us. And also, let me apologize that if I am called out for a vote in the International Relations Committee, Dr. Bartlett will assume the Chair at that point.
And so today we have five witnesses that will offer their views on this critical issue of Near-Earth Objects. Dr. David Morrison is a Senior Scientist at NASA's Ames Research Center. He will provide an overview of the hazards posed by Near-Earth Objects. And Dr. Morrison, you may proceed with your testimony. And again, thank you for being here.
STATEMENT OF DR. DAVID MORRISON, SENIOR SCIENTIST, NASA AMES RESEARCH CENTER
Dr. MORRISON. Thank you, Mr. Chairman, Members of the Committee. It is a privilege to be here, and a pleasure to return after nine years. As Mr. Gordon already noted, I reported to you earlier when I chaired the Spaceguard Survey Working Group of NASA. And I did not then—could not have hoped that by now we would actually be more than halfway through the Spaceguard Survey would have discovered more than half of the population of Near-Earth Objects larger than one kilometer, the ones that can threaten a global disaster, in fact, that we have reduced the risk of an unforeseen and unpredicted impact by more than a factor of two, thereby increasing our security.
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The nature of this risk, you have already noted, Mr. Chairman. I would like to repeat the words of this committee in 1991, which I am often quoted whenever I talk about this subject. ''The chances of the Earth being struck by a large asteroid are extremely small, but since the consequences of such a collision are very large, the Committee believes it is only prudent to assess the nature of the threat and prepare to deal with it.'' And that is what we have been doing.
You have asked me to comment, in a tutorial way, on the risk, and it can be summarized very easily. If a Near-Earth Asteroid is large enough, it has the potential to disrupt the entire global climate and produce a mass extinction, which is what happened to the dinosaurs 65 million years ago. The size limit for that is something like 10 kilometers in diameter, and I am pleased to be able to say that we have surveyed all of the Near-Earth Asteroids of that size and that none of them poses a risk of any extinction level event.
Chairman ROHRABACHER. Could I ask you to describe that again? Excuse me. How many—how big is that in terms of miles and——
Dr. MORRISON. Something about eight or ten miles across, about the size of the Washington Beltway. And those guys have been surveyed, and they are not a danger.
The next level where the current survey concentrates, is on objects larger than about a mile in diameter. One kilometer is the metric we use. Of those, there are roughly 1,100. More than half of them have already been found. These are the ones that, while they would not produce an extinction level event if they hit the Earth, nevertheless, would produce an ecological catastrophe of a magnitude to cost crop loss and perhaps a breakdown of civilization. These are the asteroids large enough to have a global effect. So you are at risk from such an impact no matter where it hits on the Earth. This is the greatest source of risk we face today from asteroids, and it is the focus of the Spaceguard Survey.
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We are, perhaps, fortunate that these large one constitute the majority of the risk and are the easiest to deal with. Our objective now is to complete the Spaceguard Survey to meet the Spaceguard goal of finding 90 percent of these objects by 2008. And as I believe Dr. Weiler will describe, we are well on the way to doing that.
If we should choose to expand the Survey, then we would look next at the size impacts that, while they could not produce a global disaster, nevertheless, could inflict very great damage, especially if the impacting object struck in the ocean and produced a tidal wave or tsunami where an impact in the center of an ocean could actually do severe damage to the cities on both sides around the whole ocean rim.
These are asteroids roughly in the 200-, 300-, 400-meter size. Some research has been done on this, but not a great deal. It would be very important if we were going to consider expanding to smaller size, that a careful community study be done to determine exactly what the risk is and to develop an optimum strategy for such a search. And to my knowledge, no such study has yet been carried out.
Smaller than that, the risk is smaller yet. And at some level, we simply have to decide how much effort is appropriate to deal with this in comparison with other natural hazards, which also demand attention. And this is a priority issue that is not a scientific issue, but one for people like you to deal with.
I will conclude by noting that we are the first generation of humans to recognize this danger. We are the first ones with the technology to detect the asteroids. We are well on the way to the first and most important stage of dealing with NEAs larger than a mile in diameter, which are, indeed, the ones that pose the greatest risk to us.
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I look at the search for NEAs, the Spaceguard Survey, a little like taking out fire insurance on your home. When you buy the insurance, you don't expect that your home will ever burn. In fact, the great majority of us will never experience a fire, yet we buy insurance to protect even against an unlikely event, because our homes are too valuable to lose. In a similar way, we undertake the Spaceguard Survey not because we expect an impact within our lifetimes or our children's lifetimes, but because the consequences of such impact would be too horrendous to be acceptable. Thank you.
[The prepared statement of Dr. Morrison follows:]
PREPARED STATEMENT OF DAVID MORRISON
Mr. Chairman and Members of the Subcommittee:
It is an honor to return to this committee almost ten years after my first appearance in 1993. At that time I presented the conclusions of the NASA workshop that proposed a Spaceguard Survey to search for potentially threatening asteroids large enough to endanger civilization. Ten years ago there was very little recognition or support outside this committee for dealing with the asteroid impact hazard. I could not have predicted then that by 2002 we would already be past the halfway mark in discovering these large Earth approaching asteroids. Thanks to the Spaceguard Survey, we can now assert that we have reduced the risk from an unforeseen catastrophic impact by more than a factor of two. This is a notable achievement in an effort to protect humanity from the worst known class of natural disasters.
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The nature of this risk was stated well by this committee in 1991, when you wrote: ''The chances of the Earth being struck by a large asteroid are extremely small, but since the consequences of such a collision are extremely large, the Committee believes it is only prudent to assess the nature of the threat and prepare to deal with it. We have the technology to detect such asteroids and to prevent their collision with the Earth.''
The Nature of the Impact Hazard
It is only during the past decade that we have come to appreciate that impacts by asteroids and comets (often called Near-Earth Objects, or NEOs) pose a significant hazard to life and property. Comet impacts constitute only about 10 percent of the risk, so the focus of my remarks is on the more common impacts by Near-Earth Asteroids, or NEAs. The most catastrophic of these are the extinction level events that can create a severe global environmental disaster. The impact of an asteroid about 10 miles in diameter (as large as the Washington beltway) 65 million years ago not only ended the existence of the dinosaurs, it wiped out more than 99 percent of all life on Earth. Fortunately for us, such mass extinction events are extremely rare. We can already state with assurance that there are no asteroids this large with orbits that could pose a threat to us. We are safe (for the present) from such impacts, but not from the smaller NEAs that actually dominate the current risk.
The greatest risk today is associated with NEAs large enough to perturb the Earth's climate on a global scale by injecting large quantities of dust into the stratosphere. These are not extinction level impacts, but they are still large enough to temporarily depress temperatures around the globe, leading to massive loss of food crops and possible breakdown of society. Various studies have suggested that the minimum mass impacting body to produce such global consequences is several tens of billions of tons, resulting in a ground burst explosion with energy in the vicinity of a million megatons of TNT—many times greater than the sum off all the world's nuclear stockpiles. The corresponding threshold diameter for NEAs is between 1 and 2 km, or roughly one mile in diameter. Current investigation, including the Spaceguard Survey, focuses on these global threats. It is entirely appropriate that we deal first with the worst danger, even though the probability of an impact in this class is exceedingly small.
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After NEAs that are large enough to risk a global catastrophe, we naturally turn our attention to smaller impacts that never-the-less would be capable of destruction on a vast scale, killing tens of millions of people. These are impacts by NEAs less than 1 km in diameter, but still large enough to devastate a large region. Such sub-kilometer NEAs are most dangerous, in fact, if they strike in the oceans. The resulting tidal wave or tsunami is an effective way to carry the energy of the collision to large distances from the point of impact. The tsunami from the ocean impact of a NEA 500 m in diameter could inundate many coastal cities in a single event. While not posing as great a risk as the global scale impact from NEAs more than 1 km in diameter, the danger from such ocean impacts may eventually be judged great enough to warrant action.
At even smaller sizes, NEA impact can still do a great deal of damage on a local scale. We have witnessed one example of such a small impact, which took place in Siberia in 1908. The energy of the explosion was about 15 megatons, and it destroyed more than 1000 square miles of forest. However, such impacts actually pose a much smaller risk than many other natural disasters, such as earthquakes and hurricanes.
It is fortunate for us that the greatest danger is posed by the largest NEAs, which are the easiest to discover. We are finding these at a rate that will allow us to retire that risk within a few more years (unless we find that one of these objects is on a collision course with Earth). As discovery techniques improve, we can shift our search toward smaller NEAs. How far to go depends on analysis of the costs and benefits of a particular defense scheme.
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Risk Estimates
Based on our recent observations, astronomers have concluded that there are between 900 and 1300 NEAs larger than 1 km that could potentially pose a threat. We can estimate the risk we each run from these impacts, which is about 1 in a million per year. This is similar to the risk of one round-trip commercial air flight. The risk from smaller impacts is less, roughly one in ten million. These are all very low numbers. The asteroid impact hazard is an extreme example of a risk of very low probability but potentially catastrophic consequences.
Much effort has gone into estimating the statistical frequency of impacts and evaluating their consequences. However, from a policy perspective we do not need precise estimates of either the frequency of impacts or their consequences. We recognize that the actual risk is not statistical; if there is any sizable asteroid on a collision course with the Earth, it can be found and the impact predicted decades (or more) in advance. Our objective should be to find any large impactor far in advance, and thus provide decision-makers with options for dealing with the threat and defending our planet from a cosmic catastrophe. That is the purpose of the Spaceguard Survey.
The Spaceguard Goal
Half-a-dozen specially designed telescopes today are contributing to the Spaceguard Survey. As mandated by this committee in 1995, the objective of the Spaceguard Survey is to find the NEAs larger than 1 km in diameter—that is, to find any with the potential for global catastrophe if they collided with Earth. Specifically the Spaceguard goal is to find 90 percent of these NEAs by the end of 2008. The philosophy of Spaceguard is to monitor a large volume of space around the Earth using automated wide-field optical telescopes with advanced detectors and computational capability. Any asteroid that could hit the Earth will repeatedly pass close to our planet, providing plenty of opportunity for discovery. Once the NEA is discovered, its orbit is computed and its position is predicted for many decades in advance. Such long-term predictions are possible because the solar system is actually a very well behaved place; asteroids do not alter their orbits capriciously. If there is the possibility of collision in the future, we expect to have decades or even centuries of advanced warning.
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Note that Spaceguard is not a last-minute warning system that attempts to find incoming objects on their final plunge toward impact. Such a system would be more complex and expensive than the current approach, and the few days or hours of warning it might provide would be insufficient to take defensive action in any case. The Spaceguard approach of cataloging all potentially dangerous NEAs is cost-effective and will yield the long lead times needed to effectively mitigate any future impacts.
Key Issues to Be Addressed After the Spaceguard Survey
The current Spaceguard program is focused on the NEAs that pose the greatest risk. Today the Spaceguard telescopes are finding many NEAs smaller than 1 km, but the level of completeness for such sub-kilometer asteroids is rather low. A logical next target might be NEAs in the range of 200–300 m diameter, since these pose the greatest tsunami danger. (Below this size, the total risk is much smaller.) Approximately 50,000 NEAs exist larger than 300 m in diameter, so the technical challenge is substantial. However, the exact target size, if any, could be above or below this range, and will need to be the subject of broad discussion within and outside the science community. Data from the existing Spaceguard Survey, as well as numerical simulations, will provide us with the information we need to make informed choices about future search goals. Once the target size is known, search strategies and requirements for smaller asteroids would need to be subject to trade studies and external review to ensure that we are getting the most effective survey possible for our investment.
Conclusion
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We are the first generation of humans that both appreciates the long-term threat of cosmic impacts and has the technological capability to deal with it. However, this is one of many natural hazards that we face, and I believe that the costs as well as the effectiveness of the surveys need to be considered in the allocation of resources to deal with this hazard.
The search for NEAs is a little like taking out fire insurance for your home. You do not expect your home to burn. The great majority of us will never experience a fire. Yet we buy insurance to protect against even such an unlikely event, because our homes are too valuable to lose. In a similar way, we undertake the Spaceguard Survey, not because we expect an impact within our lifetimes, but because the consequences of an impact would be too horrendous to be acceptable.
BIOGRAPHY FOR DAVID MORRISON
David Morrison is the Senior Scientist at the NASA Astrobiology Institute, where he participates in a variety of research programs in astrobiology—the study of the living universe. From 1996–2001 he was the Director of Space at NASA Ames Research Center, managing basic and applied research programs in the space, life, and Earth sciences.
Dr. Morrison received his Ph.D. in astronomy from Harvard University, and until he joined NASA he was Professor of Astronomy at the University of Hawaii.
Internationally known for his research on small bodies in the solar system, Dr. Morrison is the author of more than 125 technical papers and has published a dozen books. He is the recipient of the Dryden Medal for research from the American Institute of Aeronautics and Astronautics, of the Klumpke-Roberts award of the Astronomical Society of the Pacific for contributions to science education, and of the Presidential Meritorious Rank. Dr. Morrison chaired the NASA Spaceguard Survey Working Group that made the initial recommendation in 1992 for a Spaceguard Survey of NEOs, and he testified before the House Subcommittee on Space and Aeronautics in 1993 on this topic.
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Currently he is the President of the International Astronomical Union Working Group on NEOs. He received a NASA Outstanding Leadership medal for his contributions to understanding the hazard of asteroid and comet impacts, and asteroid 2410 Morrison is named in his honor.
Chairman ROHRABACHER. You mean, we don't know anything about the objects that if they land in the ocean, that could create a wave big enough to wipe out Southern California? Is that what you are saying?
Dr. MORRISON. The current survey is finding many of those objects. And they are also entirely safe, but we do not have a survey in place that will lead to a complete survey or a 90-percent survey within the near future.
Chairman ROHRABACHER. For those of us who live near the ocean, I mean, it is some comfort that we understand all about these objects that could destroy the whole Earth, but it would be even more comfortable to know that we know about the objects that could destroy all of Southern California. So anyway, pardon me.
Our next witness is Dr. Edward Weiler, and he is the NASA Associate Administrator for Space Science. Dr. Weiler will discuss NASA's current mandate in conducting a comprehensive survey of Near-Earth Objects, and he may have some comment on what I just mentioned as well.
STATEMENT OF DR. EDWARD J. WEILER, ASSOCIATE ADMINISTRATOR, NASA OFFICE OF SPACE SCIENCE
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Dr. WEILER. Good morning, Mr. Chairman, and Members of the Subcommittee. I am pleased to be here today to give you an update on NASA's Near-Earth Object, or NEO, Program.
I am quite proud of our achievements in this area. To date, NASA has identified 619 NEOs with a diameter of one kilometer or greater.
[Chart]
As you can see from the chart, this puts us well on our way to attaining our metric and our commitment to Congress of cataloguing 90 percent of NEOs in that class by the end of 2008. However, that is only part of the effort. NASA's Space Science Enterprise is dedicated to discovering more about these primitive bodies. Our exploration efforts to date, and those on the horizon in our current run-out budget, total $1.6 billion.
Some of those missions, all of which were peer-reviewed and competitively selected include NEAR–Shoemaker, which after sending back important data on asteroids 253 Mathilde and Eros actually landed on the surface of Eros, providing close-up decent images never imagined by the scientific community as captured in this image. That image, Mr. Rohrabacher, the smallest object you are looking at, is four inches across. The smallest—the resolution of that image, you are seeing objects as small as four inches across. And that is an NEO. That is the type of body we are talking about.
Other missions include Deep Impact, Stardust, Deep Space 1, and DAWN. As you can see, this is a multi-faceted program of orbital and sample return missions that promise to increase exponentially our knowledge of these types of bodies. We, of course, regret that we will not have the data that we had hoped to derive from the CONTOUR Mission, but we may very well have another cometary mission proposed in response to future announcements of opportunity in our Discovery Program.
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In your letter of invitation, you asked me to address what I envision NASA's role to be in future NEO detection. NASA is a space agency, therefore, I believe that our involvement in any potential or expanded future NEO activity should be limited to those endeavors which require a space-based platform. There are other Federal entities with far more expertise in ground-based telescope developments and observations that would be more suitable candidates to lead that portion of any future NEO endeavor.
As you may know, there is a debate in the scientific community as to whether or not it would be prudent to attempt to identify NEOs with smaller diameters, as David pointed out, the ones that could wipe out Southern California. We are actually identifying some of those now as a byproduct of our search for the larger objects.
When we have finished our sampling of the larger-than-one-kilometer class, we should have a statistically meaningful picture of the size of the population in that 100-meter to one-kilometer size range. The population is not well known at this point, nor is it clear that completing a census of all NEOs with diameters as small as 100 or 200 or 300 is even technically feasible. I recently initiated a science definition team made up of recognized experts in this field, which will consider this topic and report back to me in June of 2003.
In summary, the search for NEOs with smaller diameters is a daunting and potentially very costly test, and should not be pursued without a sound and well thought out implementation strategy with believable costs. We must also remember that characterizing these objects is just as important as identifying them, actually more important in terms of diverting a potential Earth-crossing asteroid. Sometimes the NEO debate focuses too much, in my opinion, on just categorization and not enough on understanding what these things are. Knowing their shape, their rotation, their mass, their density, their chemistry would be vitally important as this country develops potential risk mitigation capabilities. And this is the area where NASA and its space missions can make the most significant contribution.
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In that light, two bold new technology initiatives being pursued by the Space Science Enterprise: in-space propulsion, which was funded by this Congress last year, and the new Nuclear Systems Initiative, which is proposed for 2003, offer new opportunities to enable even more capable missions to NEOs earlier in the next decade. And I might add parenthetically that ultimately, if we find something coming at us and we don't have a lot of notice, we are going to want to get there fast. Having in-space propulsion and, more importantly, having nuclear electric propulsion, will enable us to get to objects much faster than our current technologies.
NASA's Space Science Enterprise has a long history of delivering outstanding science to the American public, and we intend to continue that trend with our current mission set including those missions dedicated to understanding Near-Earth Objects. Thank you, Mr. Chairman.
[The prepared statement of Dr. Weiler follows:]
PREPARED STATEMENT OF EDWARD J. WEILER
Mr. Chairman and Members of the Subcommittee: It is a privilege to be here today and report to you on the progress of NASA's Near-Earth Object (NEO) search effort. In addition to identifying NEOs, this program is also focused on determining the shapes, densities, internal structures and compositions of the NEOs and their parent population, the main-belt asteroids. I will also share with you my views on the future role of NASA with respect to exploration of these bodies.
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Background
NASA's NEO Program makes ground-based observations with the goal of identifying 90 percent of those NEOs that are 1 km or larger and characterizing a sample of them. This is a ten-year program, which began in 1998 and should be completed in 2008. (It should be noted that NASA had begun searching for NEOs many years before this program officially started.)
The threshold size for an asteroid striking the Earth to produce a global catastrophe is 1 km in diameter. NASA has an active program to detect such objects that could potentially strike the Earth and to identify their orbits. The best current estimates are that the total population of NEOs with diameters larger than 1 km is about 1000. The 1 km diameter limit for an NEO was set after extensive discussions within the scientific community to determine the size of an object that would likely threaten civilization. This community consensus is codified in the Spaceguard Report and in the Shoemaker Report. For comparison, the object that likely caused the extinction of the dinosaurs was in the 5–10 km range. The current survey of NEOs in that range is considered complete.
Status: NASA's NEO Search Program
As of the end of September, NASA has detected 619 NEOs with diameters larger than 1 km. We are currently discovering about 100 per year. At the present time, we have six groups which are funded by NASA's Near-Earth Objects program to conduct this type of research. These groups, selected though peer review, have ten telescopes among them searching for NEOs. One of these groups just completed (and another one is about to complete) major upgrades to its facility; therefore, we expect this pace of discovery to continue, if not increase. In some cases, the search programs are not able to obtain the number of observations required to determine the orbit elements of certain objects to sufficient accuracy to fully characterize the orbital parameters. These objects require additional astrometric observations, commonly called ''follow-up observations.'' We have also funded four investigations to obtain astrometric follow-up observations of those objects that cannot be easily followed by the primary search programs.
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Now, how well are we doing? I am happy to report that we are doing quite well; in fact, we are even a bit ahead of schedule. The graph below shows the discovery of NEOs over time and also the upper and lower boundaries of the likely population of NEOs with diameters larger than 1 km.
81931c.eps
There have been various reports to the effect that NASA would not reach its metric—90 percent of all the NEOs with diameters larger than 1 km—until many years after the end of 2008. However, these analyses have been based on the performance of individual search efforts, and they have tended not to use the current performance of the NEO search effort as a whole. As with most things, experience increases proficiency; therefore, we expect the rate of detection to increase. Even if we were to stay at our current rate, however, we are more than halfway to our goal of 90 percent by the end of 2008.
That does not mean we will grow complacent; we intend to continue to vigorously pursue detection of NEOs. In fact, we anticipate even better results due to technological developments such as better detector arrays, migration of existing search efforts to larger telescopes, and additional telescopes dedicated to the search program. In short, we are working to achieve both our goal and our metric and expect to be successful at both. One unanticipated result of the NEO search will be a list of over 1,000 potential candidates for future space science missions.
NASA's Future Role with Respect to NEOs
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Next I would like to turn to another question. What should NASA's role be in the future? NASA is a space agency. While we are proud of our success in implementing the Congress's direction to us with regard to the search for NEOs, we do not feel that we should play a role in any follow-on search and cataloging effort unless that effort needs to be specifically space-based in nature. There are other agencies with far more expertise in ground-based observations that would be more suitable candidates to lead that portion of a future NEO endeavor.
NASA does, however, continue to have a large role to play in the scientific space exploration of asteroids. The frequent access to space for small missions offered by NASA's Discovery Program has benefited the study of asteroids and comets as no other program to date. The first in-depth study of an NEO, Eros, was performed by the NEAR–Shoemaker mission. The body of data returned by NEAR–Shoemaker was so large, and the quality of the data so high, that NEAR's database will require years of analysis. Just this year, we initiated funding for the first 17 investigations of that data. NEAR–Shoemaker's exploration of Eros will be followed by detailed exploration of two other asteroids, Vesta and Ceres, by the upcoming DAWN mission, currently scheduled to launch in 2006. There is no reason to expect that science-driven exploration of the asteroids, and of course NEOs, will not continue through the Discovery program. We believe that the critical measurements required for developing potential mitigation efforts are substantially the same as those required to achieve the pure scientific goals identified for these objects. We must be able to understand and characterize these objects before any mitigation efforts are even considered.
In addition to NEAR and DAWN, NASA has several other missions dedicated to studying comets and asteroids, such as Deep Impact and Stardust. Our total investment in understanding these bodies, both in the past and in our current FY 2003 budget run-out, is approximately $1.6 billion. That does not even take into account those spacecraft that have provided ''bonus'' information, such as Galileo, which found a moon orbiting asteroid Ida, and Deep Space 1, a technology demonstration mission that performed a close-up fly-by of comet Borelly. NASA deeply regrets not having the potential discoveries from the recently failed CONTOUR mission, which was to have studied Comets Encke and Schwassmann-Wachmann 3.
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NASA's bold new technology initiatives, the In-Space Propulsion (ISP) Initiative and the Nuclear Systems Initiative (NSI), together offer new opportunities to enable capable new missions to NEOs early in the next decade. Improvements in solar-electric propulsion and development of solar sails are examples of new capabilities that might allow a spacecraft like NEAR–Shoemaker to visit many NEOs during a single mission rather than just one (and at the cost of a Discovery mission). If we are ever faced with the requirement to modify the motion of an NEO over time to ensure that the object will not come close to the Earth, nuclear propulsion may very well be the answer. The Nuclear Systems Initiative could address two elements in understanding the potential hazards of NEOs by: (1) providing technologies that could significantly increase our ability to identify and track NEOs, and (2) to possibly—in the future—provide sufficient power to move an Earth-intersecting object. The NSI could enable power and propulsion for an extended survey (in one mission) of multiple NEOs to determine their composition, which is a critical factor in understanding how to mitigate the risk of an Earth-intersecting object. In the future, the technologies under development by the NSI could provide us with the means to redirect the path of an Earth-intersecting asteroid, once we understand the orbital mechanics of these objects sufficiently to understand how to do this. These programs are being developed to serve a wide range of needs across NASA, but they will most certainly prove beneficial for space missions that help us to better understand and characterize NEOs.
What Should the Nation Be Doing Beyond the Current Goal?
I feel that it is premature to consider an extension of our current national program to include a complete search for smaller-sized NEOs. There are several reasons for this belief. The first is that we need to have a better understanding of the true size of the population down to at least 100 m. How will we get the improved data we need on this population? We will obtain the necessary data from the existing NASA search effort for NEOs. The search program now finds about two NEOs with diameters less than 1 km for every large one (diameter greater than 1 km) that we find. In addition, we are supporting a search program which is optimized to detect smaller NEOs. We expect by the end of this decade to have a much better picture of the true size of the population, and hence, what will be required to detect all of them.
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The second issue is how such a search could be most efficiently and cost-effectively implemented. Two groups that wish to build large survey systems have argued that the search goal should be extended to 300 m. NASA has at least two concerns with this proposition. First, we do not possess a non-advocate trade study to tell us how best to do such a search. For example, one issue to be addressed is whether it would be better to build one large 8 m class telescope or 24 m search telescopes. At these sizes, is a space-based system an option? Second, why 300 m? The present limiting diameter of 1 km was the product of a broad public discussion. When we have another broad public discussion, the answer could be: ''Leave the present limiting diameter as it stands.'' Or, perhaps the result of broad national debate on this issue would be: ''Catalog the population down to 100 m.'' We at NASA don't know the answers to these questions, and we believe that further commitments to extend the search are simply premature at this point.
Within the Office of Space Science, the Solar System Exploration Division Director has appointed a small Science Definition Team (SDT) to consider the technical issues related to extending the search for NEOs to smaller sizes. The goal of the SDT is to evaluate what is technologically possible today. The scope of the SDT does not include consideration of any change to our present NEO search goal.
Conclusion
NASA has made impressive strides in achieving its goal of cataloging 90 percent of all Near-Earth Objects with diameters of more than 1 km and characterizing a sample of them. We are currently ahead of schedule with respect to having this effort completed in the 2008 time frame. While NASA certainly agrees that because these objects pose a potential threat to the Earth, they should be studied and understood, we respectfully defend our position that any expansion of NASA's current NEO effort is premature. Before any further effort is undertaken, we would want input from the scientific community as to how this subject should be approached, and if indeed NASA is even the proper agency to lead this type of an undertaking. I will be happy to expand on any of these thoughts during the question-and-answer period. Thank you, Mr. Chairman and Members of the Subcommittee.
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BIOGRAPHY FOR EDWARD J. WEILER
Dr. Weiler was named the NASA Associate Administrator for Space Science in 1998. Under his leadership, NASA's Space Science Enterprise has had numerous successes, including the Chandra, NEAR, MAP, FUSE and Mars Odyssey missions. According to the 2001 Science News metric of contributions to world discoveries and technological achievement, Space Science's contribution is at a six-year high of 6.9 percent. Sharing the excitement of these scientific discoveries is an important part of Dr. Weiler's philosophy, and the Space Science Enterprise's interaction and partnership with the academic community and the informal education community (e.g., planetaria, museums) has grown exponentially in recent years.
Prior to his appointment as Associate Administrator, Dr. Weiler served as the Director of the Astronomical Search for Origins Program at NASA Headquarters in Washington, D.C. since March 1996. He served as the Chief Scientist for the Hubble Space Telescope since 1979. Dr. Weiler joined NASA Headquarters in 1978 as a staff scientist and was promoted to the Chief of the Ultraviolet/Visible and Gravitational Astrophysics Division in 1979.
Prior to joining NASA, Dr. Weiler was a member of the Princeton University research staff. He joined Princeton in 1976 and was based at the Goddard Space Flight Center as the director of science operations of the Orbiting Astronomical Observatory-3 (COPERNICUS).
Dr. Weiler received his Ph.D. in astrophysics from Northwestern University in January 1976. He has published numerous papers in the scientific journals. In his role as the Hubble Space Telescope Chief Scientist, he acted as the prime scientific spokesperson for the program and has appeared on a number of national TV programs including NIGHTLINE, TODAY, GOOD MORNING AMERICA, etc. For his lead role in the Hubble science program over the past two decades, Dr. Weiler was awarded the NASA Outstanding Leadership Medal and the 1994 Presidential Rank Award of Meritorious Executive. More recent recognition of his accomplishments includes another NASA Outstanding Leadership Medal, the NASA Distinguished Service Medal, and the Distinguished Presidential Rank Award.
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Dr. Weiler was born in Chicago, Illinois in 1949.
Chairman ROHRABACHER. Thank you very much. And our next witness is Dr. Joseph Burn—Burns, excuse me. He is the Irving Porter Church Professor of Engineering and Astronomy at Cornell University. Dr. Burns will outline for us the National Academy of Sciences' recommendations of the recent Near-Earth Object Survey Report. And I welcome you, Dr. Burns. And you may proceed.
STATEMENT OF DR. JOSEPH A. BURNS, IRVING PORTER CHURCH PROFESSOR OF ENGINEERING AND ASTRONOMY, CORNELL UNIVERSITY
Dr. BURNS. Good morning, Mr. Rohrabacher, and other Members of the Committee. I am pleased to be here. Let me lead by congratulating you on the passage of the Pete Conrad bill. I think it is important to bring in the amateur community in this exciting venture.
As you stated, I am representing the Steering Committee of the National Academy of Sciences Solar System Exploration Survey. These surveys were—are commissioned by NASA every decade, obviously, in order for communities, the planetary community, in this case especially, to look at what they have accomplished so far, try and identify the important questions that remain, and what facilities are needed to answer those questions. I have placed the appendix of our report, which just came out a couple of months ago. I placed that in the—in my executive summary in case you are interested.
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We—as part of that survey of all of Solar System Exploration, we have looked at the NEO problem. And we—for that reason and for other reasons, we have identified now a new goal for NASA, and that goal is to assess the threats that our planet faces, among them being the threat posed by asteroids.
I don't need to repeat the arguments given by the other witnesses, especially David, and in fact, included in the original call to this meeting, about the threat that the asteroids pose to our species. This is a real threat with devastating consequences, as David has emphasized. There is a small probability of this event occurring in our lifetimes, but it is an inevitable event, as the record shows, the geologic record shows, over the long-term. And it is posed both by Near-Earth Asteroids as well as comets.
We need to know, as we have seen here, a census of the objects that threaten our planet, that is, the orbits, the numbers of these objects, down to very small sizes, but we also need the properties, as Dr. Weiler has mentioned. And that will require visible and infrared observations, radar observations to probe the surfaces, and ultimately missions. And in this way, by knowing their properties, we will be able to mitigate the hazards that we face once we try to deflect the objects.
Part of our study, as I said, looked at Near-Earth Objects. We decided that one way to be able to take this census would be to get a dedicated large telescope. The telescope would be about 50—I am sorry, 20 feet across. It would be a wide-field telescope, so you would be able to see much of the night sky. And you would be able to survey the entire night sky every couple of weeks. This would allow us to get down to 300 meters in size, and there are a large number of these objects. Some of them are being discovered presently, but something in the order of 50,000 objects going down to that size that will cross the Earth's path.
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We will also pick up lots of other great science with this telescope, something in the order of 100,000 supernova a year. We will be able to look at the Kuiper Belt at the outer edge of the solar system, do cosmological studies, all of this for a cost estimated at present at $125 million to $150 million.
We have suggested that both the NSF——
Chairman ROHRABACHER. Doctor, could I interrupt you for a moment?
Dr. BURNS. Yeah.
Chairman ROHRABACHER. You are suggesting building this large telescope. Are you suggesting that to be a space platform or to be on the——
Dr. BURNS. Ground-based telescope.
Chairman ROHRABACHER. Ground-based telescope. Yeah. Thank you.
Dr. BURNS. One of the questions that I was asked is why our Committee decided that the NSF and NASA should share equally in the costs of this instrument. I should first call your attention, this is an unusual arrangement, but it is not an unprecedented arrangement. And our reason for this was partly motivated by the same concerns that made the Committee on Science earlier—or a couple of years ago form a Committee in order to look at the possibility of agreements between the NSF and NASA on space missions.
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The NSF has a reputation of having difficulty completing large projects. The NSF has limited monies for large research initiatives, and many competitors for those funds, not only astronomers but many other fields, and they don't have a very good track record, I must admit, in solar system studies. They have a very small budget at present in solar system studies. On the other hand, the NASA Charter calls for ground-based support, mission support, and to identify and characterize these targets. It is important, I think, also for NASA to get involved in taking a census of what is out in the solar system so the appropriate space missions can be run.
I was also asked to address what the unusual roles between what the roles of the various agencies has to say—has—how that influenced the astronomy community. And it is an odd thing the way the NEOs are studied at present. At present, the—most of the observations are being taken on Air Force and privately owned telescopes, not on NASA telescopes. The research support of the individual scientists frequently comes from NASA, so it is an uncoordinated program that is looking at this. So I think that that maybe should be addressed.
We—lastly, I should say, to summarize, we believe systematically building an inventory of Near-Earth Objects is crucial to an improved understanding of the Earth's environment, especially the prediction of future hazards posed to our species. It is also a necessary first step toward a rational program of NASA's exploration of these bodies with spacecraft. We need to know both the properties of these objects and, in fact, there may be many interesting targets that remain undiscovered at present.
All in all, the Solar System Exploration Survey Committee believes that broad areas of planetary science, including, especially Near-Earth Object studies, would benefit very substantially from the construction of the LSST. And this would only cost a relatively small investment. Thank you.
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[The prepared statement of Dr. Burns follows:]
PREPARED STATEMENT OF JOSEPH A. BURNS
SOLAR SYSTEM EXPLORATION SURVEY RECOMMENDATIONS ON THE STUDY OF NEAR-EARTH OBJECTS
Introduction
Mr. Chairman, Ranking Minority Member, and Members of the Subcommittee: thank you for inviting me to testify on behalf of the National Academies' Solar System Exploration Survey. My name is Joseph Burns, and I am Irving Porter Church Professor of Engineering and Professor of Astronomy at Cornell University. I appear today in my capacity as a steering group member of the Solar System Exploration (SSE) Survey, and as a former chair of the National Research Council's Committee on Planetary and Lunar Exploration (COMPLEX). I was also a member of the Astronomy & Astrophysics Survey's panel on Ultraviolet and Infrared Astronomy from Space.
As you know, the Astronomy and Astrophysics community has a long history of creating, through the National Research Council (NRC), decadal surveys of their field. These surveys lay out the community's research goals for the next decade, identify key questions that need to be answered, and propose new facilities with which to conduct this fundamental research.
In April 2001, NASA Associate Administrator for Space Science Edward Weiler asked the NRC to conduct a similar survey for planetary exploration. Our report, New Frontiers in the Solar System, is the result of that activity. The Solar System Exploration Survey was conducted by an ad hoc committee of the Space Studies Board (SSB), overseen by COMPLEX. This committee was comprised of some 50 scientists, drawn from a diverse set of institutions, research areas, and backgrounds; it also received input from more than 300 colleagues. The SSE Survey had four subpanels which focused on issues pertaining to different types of solar system bodies (Inner Planets, Giant Planets, Large Satellites, and Primitive Bodies) and received direct input from COMPLEX on Mars issues and from the Committee on the Origins and Evolution of Life on issues pertaining to Astrobiology.
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New Frontiers in the Solar System (the Executive Summary is appended to this statement) recommends a scientific and exploration strategy for NASA's Office of Space Science that will both enable dramatic new discoveries in this decade and position the agency to continue to make such discoveries well into the future. Your invitation indicated that I should focus on the conclusions that the SSE Survey reached in the area of Near-Earth Objects (NEOs).
Near-Earth Objects
The SSE Survey's charge from NASA included a request to summarize the extent of our current understanding of the solar system. This task was delegated to the subpanels, which in the particular case of NEOs was handled by the Primitive Bodies Panel.
Scientifically, the history of impacts on the Earth is vital for understanding how the planet evolved and how life arose. For example, it has been suggested that a majority of the water on this planet was delivered by comet impacts. A better known example of the role of impacts is the Cretaceous-Tertiary event that led to global mass extinctions, including that of the dinosaurs. Another case is the 20 megaton (MT) equivalent-energy explosion that devastated 2000 square-kilometers of pine forest in the Siberian tundra in 1908. The SSE Survey identifies the exploration of the terrestrial space environment with regards to potential hazards as a new goal for the Nation's solar system exploration enterprise.
Current surveys have identified an estimated 50 percent of NEOs that have a diameter of 1 kilometer or greater and approximately 10–15 percent of objects between 0.5 and 1 km. The vast majority of these latter objects have yet to be discovered, but a statistical analysis indicates a one percent probability of impact by a 300 m body in the next century. Such an object would deliver 1000 MT of energy, cause regional devastation, and (assuming an average of 10 people per square-kilometer on Earth) result in 100,000 fatalities. The damage caused by an impact near a city or into a coastal ocean would be orders of magnitude higher. As of a year ago, 340 objects larger than a kilometer had been catalogued as Potentially Hazardous Asteroids. In addition, the number of undiscovered comets with impact potential is large and unknown.
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The Primitive Bodies panel went on to state:
''Important scientific goals are associated with the NEO populations, including their origin, fragmentation and dynamical histories, and compositions and differentiation. These and other scientific issues are also vital to the mitigation of the impact hazard (emphasis added), as methods of deflection of objects potentially on course for an impact with Earth are explored. Information especially relevant to hazard mitigation includes knowledge of the internal structures of near-Earth asteroids and comets, their degree of fracture and the presence of large core pieces, the fractal dimensions of their structures, and their degree of cohesion or friction.''
While almost all of the SSE Survey's recommendations involved NASA flight missions, the Primitive Bodies subpanel recommended that ground-based telescopes be used to do a majority of the study of NEOs, supplemented by airborne and orbital telescopes.
A survey for NEOs demands an exacting observational strategy. To locate NEOs as small as 300 m requires a survey down to 24th magnitude (16 million times fainter than the feeblest stars that are visible to the naked eye). If images are to be taken every 10 sec to allow the sky to be studied often, the necessary capability is almost 100 times better than that of existing survey telescopes. NEOs spend only a fraction of each orbit in Earth's neighborhood, where they are most easily seen. Repeated observations over a decade would be required to explore the full volume of space populated by these objects. Such a survey would identify several hundred NEOs per night and obtain astrometric (positional) measurements on the much larger (and growing) number of NEOs that it had already discovered. Precise astrometry is needed to determine the orbital parameters of the NEOs and to assign a hazard assessment to each object. Astrometry at monthly intervals would ensure against losing track of these fast-moving objects in the months and years after discovery.
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Large-aperture Synoptic Survey Telescope
In its most recent decadal survey, the Astronomy and Astrophysics community selected the proposed Large-aperture Synoptic Survey Telescope (LSST) as their third major ground-based priority. In addition, our SSE Survey chose LSST to be its top-ranked ground-based facility. Telescopes like HST and Keck peer at selected, very localized regions of the sky or study individual sources with high sensitivity. However, another type of telescope is needed to survey the entire sky relatively quickly, so that periodic maps can be constructed that will reveal not only the positions of target sources, but their time variability as well. The Large-aperture Synoptic Survey Telescope is a 6.5-m-effective-diameter, very wide field (3 deg) telescope that will produce a digital map of the visible sky every week. For this type of survey observation, the LSST will be a hundred times more powerful than the Keck telescopes, the world's largest at present. Not only will LSST carry out an optical survey of the sky far deeper than any previous survey, but also—just as importantly—it will also add the new dimension of time and thereby open up a new realm of discovery. By surveying the sky each month for over a decade, LSST would revolutionize our understanding of various topics in astronomy concerning objects whose brightnesses vary on time scales of days to years. NEOs, which drift across a largely unchanging sky, are easily identified. The LSST could locate 90 percent of all near-Earth objects down to 300 m in size, enable computations of their orbits, and permit assessment of their threat to Earth. In addition, this facility could be used to discover and track objects in the Kuiper Belt, a largely unexplored, primordial component of our solar system. It would discover and monitor a wide variety of variable objects, such as the optical afterglows of gamma-ray bursts. In addition, it would find approximately 100,000 supernovae per year, and be useful for many other cosmological observations.
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The detectors of choice for the temporal monitoring tasks would be thinned charge-coupled devices (CCDs); the requisite extrapolation from existing systems should constitute only a small technological risk. An infrared capability of a comparably wide field would be considerably more challenging but could evolve as the second phase of the telescope's operation. Instrumentation for LSST would be an ideal way to involve independent observatories with this basically public facility.
NASA/NSF Cooperation
Historically, the National Science Foundation (NSF) has built and operated ground-based telescopes, whereas NASA has done the same for space-based observatories. Although the Astronomy and Astrophysics Survey was noncommittal on who should build the LSST, the SSE Survey included a recommendation that NASA share equally with NSF in the telescope's construction and operations costs.
Such an arrangement has precedent. The SSE Survey noted that:
''NASA continues to play a major role in supporting the use of Earth-based optical telescopes for planetary studies. It funds the complete operations of the IRTF (InfraRed Telescope Facility), a 3 m diameter telescope located on Hawaii's Mauna Kea. In return for access to 50 percent of the observing time for non-solar-system observations, the NSF supports the development of IRTF's instrumentation. This telescope has provided vital data in support of flight missions and will continue to do so. As another example, NASA currently buys one-sixth of the observing time on the privately operated Keck 10 m telescopes. This time was purchased to test interferometric techniques in support of future spaceflight missions such as SIM (Space Interferometry Mission) and TPF (Terrestrial Planet Finder).''
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The solar system exploration community is concerned that the NSF is often unwilling to fund solar system research. This is particularly unfortunate given NSF's charter to support the best science and its leadership role in other aspects of ground-based astronomy.
The shared responsibility between NASA and the NSF that we recommend is also endorsed by the more general findings last year of the NRC's Committee on the Organization and Management of Research in Astronomy and Astrophysics (COMRAA), chaired by Norman Augustine. COMRAA's report recommended that NASA continue to ''support critical ground-based facilities and scientifically enabling precursor and follow-up observations that are essential to the success of space missions.'' COMRAA also noted that in 1980 the NSF provided most of the research grants in astronomy and astrophysics, but today NASA is the major supporter of such research.
The roles of the agencies also affect the ability of scientists to conduct a census of Near-Earth Objects. The SSE Survey commented that:
''interestingly enough, NASA has no systematic survey-capability to discover the population distribution of the solar-system bodies. To do this, NASA relies on research grants to individual observers who must gain access to their own facilities. The large NEOs are being efficiently discovered using small telescopes for which NASA provides instrumentation funding, but all the other solar system populations—e.g., comets, Centaurs, satellites of the outer planets, and Kuiper Belt Objects—are being characterized almost entirely using non-NASA facilities. This is a major deficiency. . .''
The construction of the LSST would provide a central, federally sponsored location for such research.
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LSST Costs and Survey Below 300 Meters
The costs of the LSST are projected by the 2001 Astronomy and Astrophysics Survey as being $83 million for capital construction and $42 million for data processing and distribution for five years of operation, for a total cost of $125 million. Routine operating costs, including a technical and support staff of 20 people, are estimated at approximately $3 million per year. The LSST will be able to routinely discover and characterize NEOs down to 300 m in diameter. Increasing the sensitivity of the survey to 100 m would mean increasing the sensitivity of the telescope by a factor of ten. This may represent a ''beyond the state-of-the-art'' challenge to telescope builder, and certainly a much larger telescope—three times the LSST and probably 10 to 100 times the cost unless innovative designs are found. The number of discovered objects would correspondingly increase substantially; this large data set may challenge current capabilities.
Concluding Thoughts
By way of summary, let me place the LSST into the context of a robust scientific program. Systematically building an inventory of the Near-Earth Objects is crucial to an improved understanding of Earth's environment, especially to the prediction of future hazards posed to our species. It is also a necessary first step towards a rational program of NASA's exploration of these bodies with spacecraft: many of the most interesting targets may remain, as yet, undiscovered. The ability to create and play a ''motion picture'' of the night sky will also provide new insights in a wide variety of disciplines from cosmology to astrophysics to solar system exploration. A suitable analog might be the deepened knowledge that is obtained from dynamic movies of swirling clouds and weather patterns, as compared to an occasional static photo.
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The immense volume of data from the LSST would provide a reservoir of information for numerous graduate students and researchers, as well as established scientists. Further, LSST will support flight missions—for example, identifying possible fly-by targets for a spacecraft mission to explore the Kuiper Belt. All in all, the SSE Survey committee believes that broad areas of planetary science, particularly NEO studies, would benefit very substantially from the construction of the LSST for a relatively small investment.
Thank you again, Mr. Chairman, for the opportunity to appear before the subcommittee today. I would be glad to answer any questions that you or your subcommittee members may have.
APPENDIX A
BIOGRAPHY FOR JOSEPH A. BURNS
Joseph A. Burns is the I.P. Church Professor of Engineering and Astronomy at Cornell University, where most of his professional life has been spent. He is a member of the Steering Committee of the just-completed Solar System Exploration Decadal Survey of the National Research Council; in the mid-1990s he had chaired a similar survey. He also served on one of the panels for the Astronomy and Astrophysics Decadal Survey (2000). His areas of research are planetary dynamics and the solar system's structure. Burns is a member of three spacecraft imaging teams. Using ground-based telescopes and spacecraft, his students have discovered several planetary rings and about twenty small satellites of the giant planets.
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Starting in the late 1970s Burns edited Icarus, the principal journal of planetary science, for about twenty years. He is presently is a Reviewing Editor of the journal Science. Burns is a Vice President of the American Astronomical Society and he has led its Divisions of Planetary Science (DPS) and on Dynamical Astronomy. He is a fellow of the American Geophysical Union and the American Association for the Advancement of Science, as well as a member of the Russian Academy of Sciences and the International Academy of Astronautics. Burns holds the USSR's Schmidt Medal and the DPS' Masursky Prize as well as three NASA medals for scientific achievement.
APPENDIX B
New Frontiers in the Solar System
Executive Summary
Solar system exploration is that grand human endeavor which reaches out through interplanetary space to discover the nature and origins of the system of planets in which we live and to learn whether life exists beyond Earth. It is an international enterprise involving scientists, engineers, managers, politicians, and others, sometimes working together and sometimes in competition, to open new frontiers of knowledge. It has a proud past, a productive present, and an auspicious future.
Solar system exploration is a compelling activity. It places within our grasp answers to basic questions of profound human interest: Are we alone? Where did we come from? What is our destiny? Further, it leads to the creation of knowledge that will improve the human condition. Mars and icy satellite explorations may soon provide an answer to the first of these questions. Exploration of comets, primitive asteroids, and Kuiper Belt objects may have much to say about the second. Surveys of near-Earth objects and further exploration of planetary atmospheres will say something about the third. Finally, explorations of all planetary environments will result in a much-improved understanding of the natural processes that shape the world in which we live.
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This survey was requested by the National Aeronautics and Space Administration (NASA) to determine the contemporary nature of solar system exploration and why it remains a compelling activity today. A broad survey of the state of knowledge was requested. In addition, NASA asked for identification of the top-level scientific questions to guide its ongoing program and a prioritized list of the most promising avenues for flight investigations and supporting ground-based activities. To accomplish this task, the Solar System Exploration Survey's (SSE Survey's) Steering Group and panels have worked with scientists, professional societies, NASA and National Science Foundation (NSF) officials, people at government and private laboratories, and members of the interested public. The remarkable breadth and diversity in the subject are evident in the panel reports that are contained in Part One of this survey. Together they strongly reinforce the idea that a high-level integration of the goals, ideas, and requirements that exist in the community is essential if a practical exploration strategy for the next decade is to emerge. Such an integrated strategy is the objective of Part Two.
CROSSCUTTING THEMES AND KEY QUESTIONS
Based on the material presented in Part One of this report, the SSE Survey has identified four recurring issues, or crosscutting themes, that form an appropriate basis for an integrated strategy that can be realized by a series of missions to be flown over the next decade. The four crosscutting themes are as follows:
1. The First Billion Years of Solar System History. This first theme covers the formative period that features the initial accretion and development of Earth and its sibling planets, including the emergence of life on our globe. This pivotal epoch in the solar system's history is only dimly glimpsed at present.
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2. Volatiles and Organics: The Stuff of Life. The second theme addresses the reality that life requires organic materials and volatiles, notably, liquid water. These materials originally condensed in the outer reaches of the solar nebula and were later delivered to the planets aboard organic-rich comets and asteroids.
3. The Origin and Evolution of Habitable Worlds. The third theme recognizes that our concept of the ''habitable zone'' has been overturned, and greatly broadened, by recent findings on Earth and elsewhere throughout our galaxy. Taking inventory of our planetary neighborhood will help to trace the evolutionary paths of the other planets and the eventual fate of our own.
4. Processes: How Planetary Systems Work. The fourth theme seeks deeper understanding of the fundamental mechanisms operating in the solar system today. Comprehending such processes—and how they apply to planetary bodies—is the keystone of planetary science. This will provide deep insight into the evolution of all the worlds within the solar system and of the multitude of planets being discovered around other stars.
Devolving from these four crosscutting themes are 12 key scientific questions. These are shown in Table ES.1, together with the names of the facilities and missions recommended as the most appropriate activities to address these questions. The priority and measurement objectives of these various projects are summarized in the next section.
PRIORITIES FOR FLIGHT MISSIONS AND ADVANCED TECHNOLOGY
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Progress on the tabulated scientific themes and key questions will require a series of spaceflights and supporting Earth-based activities. It is crucial to maintain a mix of mission sizes and complexities in order to balance available resources against potential schemes for implementation. For example, certain aspects of the key science questions can be met through focused and cost-effective Discovery missions (<$325 million), while other high-priority science issues will require larger, more capable projects, to be called New Frontiers. About once per decade, Flagship missions (>$650 million) will be necessary for sample return or comprehensive investigations of particularly worthy targets. Some future endeavors are so vast in scope or so difficult (e.g., sample return from Mars) that no single nation acting alone may be willing to allocate all of the resources necessary to accomplish them, and the SSE Survey recommends that NASA encourage and continue to pursue cooperative programs with other nations. Not only is the investigation of our celestial neighborhood inherently an international venture, but the U.S. Solar System Exploration program will also benefit programmatically and scientifically from such joint ventures.
Discovery missions are reserved for innovative and competitively procured projects responsive to new findings beyond the Nation's long-term strategy. Such missions can satisfy many of the objectives identified in Part One by the individual panels. Given Discovery's highly successful start, the SSE Survey endorses the continuation of this program, which relies on principal-investigator leadership and competition to obtain the greatest science return within a cost cap. A flight rate of no less than one launch every 18 months is recommended.
Particularly critical in this strategy is the initiation of New Frontiers, a line of medium-class, principal-investigator-led missions as proposed in the President's fiscal year (FY) 2003 budget. The SSE Survey strongly endorses the New Frontiers initiative. These spacecraft should be competitively procured and should have flights every two or three years, with the total cost capped at approximately twice that of a Discovery mission. Target selection should be guided by the list in this report.
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Experience has shown that large missions, which enable detailed, extended, and scientifically multifaceted observations, are an essential element of the mission mix. They allow the comprehensive exploration of science targets of extraordinarily high interest. Comparable past missions have included Viking, Voyager, Galileo, and Cassini-Huygens. The SSE Survey recommends that Flagship (>$650 million) missions be developed and flown at a rate of about one per decade. In addition, for large missions of such inclusive scientific breadth, a broad cross section of the community should be involved in the early planning stages.
Programmatic efficiencies are often gained by extending operational flights beyond their nominal lifetimes. Current candidates for continuation include Cassini, projects in the Mars Exploration Program, and several Discovery flights. The SSE Survey supports the current Senior Review process for deciding the scientific merits of a proposed mission extension and recommends that early planning be done to provide adequate funding of mission extensions, particularly Flagship missions and missions with international partners.
Because resources are finite, the SSE Survey prioritized all new flight missions within each category along with any associated activities. To assess priorities in the selection of particular missions, it used the following criteria: scientific merit, ''opportunity,'' and technological readiness. Scientific merit was measured by judging whether a project has the possibility of creating or changing a paradigm and whether the new knowledge that it produces will have a pivotal effect on the direction of future research, and, finally, on the SSE Survey's appraisal of how that knowledge would substantially strengthen the factual base of current understanding.
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Because of wide differences in mission scope and the diverse circumstances of implementation, the SSE Survey, at NASA's request, prioritized only within three cost classes: small (<$325 million), medium ($325 million to $650 million), and large (>$650 million). Also, since the Mars Exploration Program line is already successfully established as a separate entity within NASA, its missions are prioritized separately in this report.
The recommendations from the SSE Survey's panels have been integrated with the Solar System Exploration program's overall goals and key questions in order to arrive at the flight-mission priorities listed in Table ES.2. The SSE Survey has included five New Frontiers missions in its priority list, recognizing that not all might be affordable within the constraints of the budgets available over the next decade.
Recommended Solar System Flight Missions (non-Mars)
Europa Geophysical Explorer
The Europa Geophysical Explorer (EGE), a Flagship mission, will investigate the probable subsurface ocean of Europa and its overlying ice shell as the critical first step in understanding the potential habitability of icy satellites. While orbiting Europa, EGE will employ gravity and altimetry measurements of Europa's tidal fluctuations to define the properties of any interior ocean and characterize the satellite's ice shell. Additional remote-sensing observations will examine the three-dimensional distribution of subsurface liquid water; elucidate the formation of surface features, including sites of current or recent activity; and identify and map surface composition, with emphasis on compounds of astrobiological interest. Prior to Europa-orbit insertion, EGE's instruments will scrutinize Ganymede and Callisto, moons that also may have subsurface oceans, thereby illuminating Europa's planetary and astrobiological context. Europa's thorough reconnaissance is a stepping-stone toward understanding the astrobiological potential of all icy satellites and will pave the way for future landings on this intriguing object.
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Kuiper Belt-Pluto Explorer
The Kuiper Belt-Pluto Explorer (KBP) will be the first spacecraft dispatched for scientific measurements within this remote, entirely unexplored outer half of the solar system. KBP will fly past Pluto-Charon and continue on to do reconnaissance of several additional Kuiper Belt objects (KBOs). KBP's value increases as it observes more KBOs and investigates the diversity of their properties. This region should be home for the most primitive material in the solar system. KBP will address the prospect that KBOs have played a role in importing basic volatiles and molecular stock to the inner solar system, where habitable environments were created. The SSE Survey anticipates that the information returned from this mission might lead to a new paradigm for the origin and evolution of these objects and their significance in the evolution of objects in other parts of the solar system.
South Pole-Aitken Basin Sample Return
The South Pole-Aitken Basin Sample Return (SPA–SR) mission will return samples from the Moon in order to constrain the early impact history of the inner solar system and to comprehend the nature of the Moon's upper mantle. The South Pole-Aitken Basin, the largest impact structure known in the solar system, penetrates through the lunar crust. It is stratigraphically the oldest and deepest impact feature preserved on the Moon. The SPA–SR mission will help determine the nature of the differentiation of terrestrial planets and provide insight into the very early history of the Earth-Moon system. SPA–SR will also enable the development of sample acquisition, handling, and return technologies to be applied on other future missions.
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Jupiter Polar Orbiter with Probes
The Jupiter Polar Orbiter with Probes (JPOP) mission will determine if Jupiter has a central core, a key issue that should decide between the two competing scenarios for the planet's origin. It will measure water abundance, which plays a pivotal role in understanding giant planet formation. This parameter indicates how volatiles (HO, CH, NH, and HS) were incorporated in the giant planets and, more specifically, the degree to which volatiles were transported from beyond Neptune to the inner solar system. The mission will probe the planet's deep winds to at least the 100-bar pressure level and may lead to an explanation of the extreme stability of the cloud-top weather systems. From its cloud-skimming orbit, JPOP will investigate the fine structure of the planet's magnetic field, providing information on how its internal dynamo works. Lastly, the spacecraft will repeatedly visit the hitherto-unexplored polar plasma environment, where magnetospheric currents crash into the turbulent atmosphere to generate powerful aurorae.
Venus In Situ Explorer
On descent, the Venus In Situ Explorer (VISE) mission will make compositional and isotopic measurements of the atmosphere and—quickly—of the surface. It will loft a core sample from Venus's hellish surface to cooler altitudes, where further geochemical and mineralogical data will be obtained. VISE will provide key measurements of the lower atmosphere and of surface-atmosphere interactions on Earth's would-be twin. The project will elucidate the history and stability of Venus's atmospheric greenhouse and its bizarre geological record. It will also advance the technologies required for the sample return from Venus expected in the following decade.
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Comet Surface Sample Return
The Comet Surface Sample Return (CSSR) mission will collect materials from the near surface of an active comet and return them to Earth for analysis. These samples will furnish direct evidence on how cometary activity is driven. Information will be provided on the manner in which cometary materials are bound together and on how small bodies accrete at scales from microns to centimeters. By comparing materials on the nucleus against the coma's constituents, CSSR will indicate the selection effects at work. It will also inventory organic materials in comets. Finally, CSSR will yield the first clues on crystalline structure, isotopic ratios, and the physical relationships between volatiles, ice, refractory materials, and the comet's porosity. These observations will give important information about the building blocks of the planets.
Small Missions
Recommendations for small missions include a series of Discovery flights at the rate of at least one every 18 months and an extension to the Cassini-Huygens mission (Cassini Extended), presuming that the nominal mission is successful. Discovery missions are, by intent, not subject to long-term planning. Rather, they exist to create frequent opportunities to fly small missions addressing fundamental scientific questions and to pursue new research problems in creative and innovative ways.
Recommended Mars Flight Missions
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For Mars exploration, the SSE Survey endorses the current science-driven strategy of seeking (i.e., remote sensing), in situ measurements (science from landers), and sampling to understand Mars as a planet, understand its astrobiological significance, and afford unique perspectives about the origin of life on Earth. The evolution of life and planetary environments are intimately tied together. To understand the potential habitability of Mars, whether it has or has not supported life, we must understand tectonic, magmatic, and hydrologic evolution as well as geochemical cycles of biological relevance. The return of materials from known locations on Mars is essential in order to address science goals, including those of astrobiology, and to provide the opportunity for novel measurements, such as age-dating and ultimate ground-truth.
Mars Smart Lander
The Mars Smart Lander (MSL) mission will conduct in situ investigations of a water-modified site that has been identified from orbit. It will provide ground truth for orbital interpretations and test hypotheses for the formation of geological features. The types of in situ measurements possible include atmospheric sampling, mineralogy and chemical composition, and tests for the presence of organics. The mission should either drill to get below the hostile surface environment or have substantial ranging capability. While carrying out its science mission, MSL should test and validate technology required for later sample return.
Mars Long-Lived Lander Network
The Mars Long-Lived Lander Network (MLN) is a grid of science stations making coordinated measurements around Mars's globe for at least 1 martian year. The highest-priority objectives for network science on Mars are the determination of the planet's internal structure, including its core; the elucidation of surface and near-surface composition as well as thermal and mechanical properties; and extensive synoptic measurements of the atmosphere and weather. In addition, heat flow, atmospheric gas isotopic observations (to constrain the size of currently active volatile reservoirs), subsurface oxidizing properties, and surface-atmosphere volatile exchange processes will be valuable. This mission will complement the much-more-limited and localized French NetLander that will have four probes spaced across Mars's equatorial regions.
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Mars Sample Return
Mars Sample Return (MSR) is required in order to perform definitive measurements to test for the presence of life, or for extinct life, as well as to address Mars's geochemical and thermal evolution. Further, Mars's atmosphere and now frozen hydrosphere will require highly sophisticated measurements and analytical equipment. To accomplish key science goals, samples must be returned from Mars and scrutinized in terrestrial laboratories. For these reasons, the SSE Survey recommends that NASA begin its planning for Mars Sample Return missions so that their implementation can occur early in the decade 2013–2023. Current studies of simplified Mars sample-return missions indicate that such missions are now within technological reach. Early on, NASA should engage prospective international partners in the planning and implementation of MSR.
Small Missions
Mars Scout missions are required in order to address science areas that are not included in the core program and to respond to new discoveries derived from current and future missions. A series of such small (<$325 million) missions should be initiated within the Mars program for flights at alternating Mars launch opportunities. This program should be modeled on the Discovery program.
Mars Upper Atmosphere Orbiter (MAO) is a small mission dedicated to studies of Mars's upper atmosphere and plasma environment. This mission would provide quantitative information on the various atmospheric escape fluxes, thus quantifying current escape rates and providing a basis for backward extrapolation in our attempt to understand the evolution of Mars's atmosphere.
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Technology Directions
A significant investment in advanced technology development is also needed for the recommended new and future flight missions to better succeed. Table ES.3 identifies a number of important areas in which technology development is appropriate. The SSE Survey recommends that NASA commit to significant new investments in advanced technology so that future high-priority flight missions can succeed.
RESEARCH INFRASTRUCTURE
In an era of competitively selected missions for space exploration, it will continue to be necessary to improve the technical expertise and infrastructure of organizations providing the vital services that enable the planning and operation of all solar system exploration missions.
For missions to be the most productive scientifically, a level of funding must be ensured that is sufficient not only for the successful operation of the flight but also for the contemporaneous analysis of the data and the publication of scientific results. Moreover, the SSE Survey's mission priorities rest on a foundation that must be secured and buttressed. This foundation includes fundamental research, technology development, follow-on data analysis, ground-based facilities, sample-analysis programs, and education and public outreach activities.
The entire pipeline that brings data from distant spacecraft to the broad research community must be systematically improved. Insufficient downlink communications capacity through the Deep Space Network (DSN) currently restricts the return of data from all missions, as occasionally does the DSN's limited geographical coverage. The DSN needs to be continually upgraded as new technologies become available and system demands increase.
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Once data are on the ground, they must be swiftly archived in a widely accepted and usable format. The Planetary Data System (PDS) should be included as a scientific partner at the very early stages of missions; its must be sized to accomplish its future tasks. In order to utilize the returned information effectively, analysis programs ought to be in place to fund investigators immediately upon delivery of ready-to-use data to the PDS. Data-analysis programs should be merged across lines (e.g., Discovery, New Frontiers) rather than being tied to individual missions.
A healthy research and analysis (R&A) program is the most basic requirement for a successful program of flight missions. The SSE Survey recommends an increase over the decade in the research and analysis programs at a rate above inflation that parallels the increase in the number of missions, amount of data, and diversity of objects studied. Previous National Research Council (NRC) studies have shown that after a serious decline in the early to mid-1990s,(see footnote 2) the overall funding for R&A programs in NASA's Office of Space Science climbed in recent years to approximately 20 percent of the overall flight-mission budget.(see footnote 3) Figures supplied by NASA's Solar System Exploration program show that the corresponding value for planetary activities is currently closer to 25 percent and is projected to stay at about this level for the next several years. The SSE Survey believes that this is an appropriate allocation of resources.
NASA's Astrobiology program has appropriately become deeply interwoven into the solar system exploration research and analysis program. The SSE Survey encourages NASA to continue the integration of astrobiology science objectives with those of other space science disciplines. Astrobiological expertise should be called upon when identifying optimal mission strategies and design requirements for flight-qualified instruments that address key questions in astrobiology and planetary science.
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Ground-based telescopes have been responsible for several major discoveries in solar system exploration during the past decade. Moreover, many flight missions are greatly enhanced as a result of extensive ground-based characterization of their targets. The SSE Survey recommends that NASA partner equally with the National Science Foundation to build and operate a survey facility such as the Large-aperture Synoptic Survey Telescope (LSST), described in Astronomy and Astrophysics in the New Millennium,(see footnote 4) to ensure that LSST's prime solar system objectives are accomplished. Other powerful new facilities highlighted in that report—for example, the Next Generation Space Telescope—should be designed, where appropriate, to be capable of observing moving solar system targets. In addition, NASA should continue to support ground-based observatories for planetary science, including the planetary radar capabilities at the Arecibo Observatory in Puerto Rico and in Goldstone, California, the Infrared Telescope Facility on Mauna Kea in Hawaii, and shares of cutting-edge telescopes such as the Keck telescopes on Mauna Kea, as long as they continue to be critical to missions and/or scientifically productive.
In anticipation of the return of extraterrestrial samples from several ongoing and future missions, an analogue to the data pipeline must be developed for cosmic materials. The SSE Survey recommends that well before cosmic materials are returned from planetary missions, NASA should establish a sample-analysis program to support instrument development, laboratory facilities, and the training of researchers. In addition, planetary protection requirements for missions to worlds of biological interest will require investments, as will life-detection techniques, sample quarantine facilities, and sterilization technologies. NASA's current administrative activities to develop planetary protection protocols for currently planned missions are appropriate.
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Education and Public Outreach activities connect solar system exploration with its ultimate customers—the tax-paying public—and as such are an extremely important component of the program. Solar system exploration captures the imagination of young and old alike. By correctly illustrating the scientific method at work and demonstrating scientific principles, the planetary science community's efforts in communicating with students and lay people can be influential in helping to improve science literacy and education. In most implementations today, planetary scientists and education specialists work hand-in-hand to derive innovative and effective activities for communicating about solar system exploration with students, teachers, and the public. Although some problems remain, this program is well managed and is on a solid foundation.
CONCLUSIONS
For nearly 40 years, the U.S. Solar System Exploration program has led to an explosion of knowledge and awe with respect to our celestial neighborhood as ground-based telescopes and spacecraft have become much more capable while reaching out farther from Earth. We are now poised to address issues about our origins that have puzzled our forebears since civilization's beginning. Answers to profound questions about our origins and our future may be within our grasp. This survey describes an aggressive and yet rational strategy to deepen our analysis of such questions and finally resolve many long-standing mysteries during the next decade.
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Chairman ROHRABACHER. Thank you very much. Our next witness, Dr. Brian Marsden, is the Director of the Minor Planet Center under the auspices of the Smithsonian Astrophysiological [sic-Astrophysical] Observatory. Boy, I got that out. He will discuss the role of the Minor Planet Center and the role it plays in the Near-Earth Object Survey. Dr. Marsden?
STATEMENT OF DR. BRIAN G. MARSDEN, DIRECTOR, MINOR PLANET CENTER, SMITHSONIAN ASTROPHYSICAL OBSERVATORY
Dr. MARSDEN. Mr. Chairman, Distinguished Members of the Committee, thank you for inviting me here. It is actually astrophysical observatory, I am sorry. I am sorry to have to correct you, but I do congratulate——
Chairman ROHRABACHER. I didn't get it out after all.
Dr. MARSDEN. But I do congratulate you on the passage of H.R. 5303.
Chairman ROHRABACHER. The Chairman will have to excuse himself. You know what, being the Vice-chairman, I am going to ask Dr. Weldon to take over while I am gone. I apologize. We have got to take care of Saddam Hussein as well as these other threats, right?
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Dr. MARSDEN. The Minor Planet Center plays a key role in that it receives observations by e-mail of the sky positions of asteroids and comets many times a day from dozens of observers around the world. The MPC tries to make sense of these observations, establishing the identifications of known objects and estimating likely orbital trajectories of unknown objects that frequently link with similar calculations from observations on neighboring nights and thereby ultimately allow these objects also to become known.
Although the MPC may receive tens of thousands of observations on a given day, it is important to appreciate that only 1 to 0.1 percent of them are NEOs—most of them are main belt asteroids between Mars and Jupiter. And the NEOs are usually, but not always, recognized by their faster sky motions.
If a new object seems a likely NEO candidate, the Minor Planet Center puts a prediction of the object's position for the next couple of days in the World Wide Web on what is called the NEO Confirmation Page. Observers monitor this page, make and report confirmatory observations that allow the MPC to update the prediction. When there are enough follow-up observations to compute a reasonably definite orbit, the MPC makes a more formal electronic publication with all of the available data. That usually takes about 36 hours. Continuing observations and refined orbital calculations are then issued essentially on a daily basis.
Of the present three-member Minor Planet Center staff, one is a Federal employee at the Smithsonian, namely myself, one is paid from a contract from NASA, and one is paid from subscriptions to the Minor Planet Center publications. The Minor Planet Center's computing equipment is mainly purchased from gifts from the Tamkin Foundation of Los Angeles to the Smithsonian. A very small subvention is provided by the International Astronomical Union.
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Although more than 80 percent of the observers who provide data to the MPC are amateur astronomers, they actually contribute less than 20 percent of the observations. There are the two dominant programs, LINEAR and NEAT, as mentioned in my more complete deposition. Very occasionally an amateur will discover an NEO, but the principal contribution of the amateurs is in making follow-up observations, and we very much appreciate what they do. I think that the best encouragement to amateurs is to provide the means for them to improve their equipment, get new electronic detectors. The Planetary Society, NASA, and the Wilson Comet Award have helped very much in this connection, and I also hope that the Pete Conrad Award now on its way will do likewise.
As for the future, the MPC has responded to surges in observational activity in the past. And the current inventory of 15 million observations, this is asteroids generally, and 200,000 orbits in its files has doubled during the last 18 months or so, and that will continue to double.
The main problem we have is simply the lack of manpower. Despite its considerable experience, the present staff of three is surely insufficient to maintain the current aim of 16/7 coverage and well below what would be needed for 24/7 coverage that some would like. If we are to extend the current one kilometer, half a mile mandate of NASA down to the 200 or 300 meters that has—that had been mentioned, still more staff would obviously be needed. But I think there would need—be a need for relatively modest additions to the MPC's computing facilities and procedures. The—down—if you go down to 200 meters—well, you said 50,000 of them. I came up with 40,000, but that is okay. We have already got 1,800 of those with the existing program, and they are being added to at 400 a year. So you can see that by the end of the century, we will have most of them. So—but maybe we want to do it more quickly than that. If we are going to go down to the—to a 50-meter level, as I think the next speaker is going to discuss, then probably we will have to do searches from space, and it would be a very different proposition. And then the Minor Planet Center would probably only be a small part of a much larger organization that would be necessary to handle them. Thank you.
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[The prepared statement of Dr. Marsden follows:]
PREPARED STATEMENT OF BRIAN G. MARSDEN
Accurate measurements of the positions of asteroids and comets, including known and candidate NEOs, are received by the Minor Planet Center (located at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts) many times a day in e-mail messages from up to perhaps 150 observatories (both professional and amateur) around the world. Although something like half a million observations are received every month, it is important to appreciate that NEOs comprise only between 0.1 and 1 percent of the observations of asteroids as a whole, almost all of which are confined at quite safe distances from the Earth in what is termed the ''main belt'' between the orbits of Mars and Jupiter. Particularly when they are near the Earth, NEOs are usually recognizable by the fact that their apparent motions across the sky are greater than those of the main-belt asteroids, although when they are farther away (and, of course, fainter), the sky motions of NEOs and main-belt asteroids can be comparable and therefore not easily distinguishable.
The principal programs in the world for surveys for new NEOs are the ones bearing the acronyms LINEAR and NEAT (programs based in Massachusetts and California, respectively, that are largely funded by NASA but use USAF telescopes in New Mexico and Hawaii, the latter also in conjunction with a non-USAF telescope on Palomar Mountain in California), as well as three programs (also largely funded by NASA) using telescopes in Arizona. Data from these programs represent well over 80 percent of the observations received at the Minor Planet Center, where they generally arrive during the afternoon after the images were exposed. On its most productive nights LINEAR might record as many as 15,000 different objects, in which case the data may not reach the Minor Planet Center until evening. With typically from three to five observations of each object made over the course of 30–60 minutes the objects with the more unusual apparent motions can readily be picked out (usually by the observers themselves), and calculations are then made at the Minor Planet Center, first to check whether these objects are already known, and if not known, to identify those that seem most likely to be NEOs. Within 15–30 minutes of the receipt of the data, the Minor Planet Center is then able to place predictions of the likely sky positions (for the next day or so) of the best NEO candidates in the WWW on what is known as ''The NEO Confirmation Page.'' Observers around the world regularly check this webpage. Since afternoon in Massachusetts is already evening in Europe, it is sometimes then a matter of less than an hour before the Minor Planet Center receives confirmatory observations of the NEOs from observatories in Europe, at which point the orbit calculation can be refined and an improved prediction posted on the webpage well before it is night-time in the U.S. and further observations can be made from there. Those new U.S. observations will frequently include both further deliberate observations of the candidate NEOs and more accidental observations of the same objects by the survey programs that will come to light when the Minor Planet Center examines the next night's data from those programs.
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With three separate groups of observations (the,discovery data from LINEAR or NEAT, then ideally confirmatory data from Europe and follow-up data from North America the night after the discovery), it is usually possible to derive a moderately good estimate of the real orbit of an NEO, and at this point a unique designation is given to the object (the year, two letters and sometimes additional numerals), and all the relevant information (including appropriate credit to the observers) is collected and published on an official Minor Planet Electronic Circular, which is both distributed by e-mail and made accessible on the WWW. At the same time, the prediction on The NEO Confirmation Page is removed, in order to make way for further entries. At any given time, there might be as many as 20 or 30 NEO candidates awaiting confirmation, but by pruning the list there is more chance that the follow-up observers will concentrate on the objects most in need of attention. Of course, further refinement of the NEO orbits is still very necessary using observations made during the weeks (and also the years) after discovery, and the Minor Planet Center routinely disseminates this additional information in a ''Daily Orbit Update'' Electronic Circular that is prepared automatically in the wee hours of the morning from the data received the previous day.
The current scientific staff' of the Minor Planet Center consists of one Federal Employee (Smithsonian Institution), one person funded from a contract with NASA via the Jet Propulsion Laboratory and one person paid from subscriptions to the Minor Planet Center's publications. Allowing for absences, this is technically insufficient for the 16/7 operation the Center tries to maintain. There is clearly a need for at least two more employees, including a systems engineer who would be charged with maintaining the Center's cluster of computers, which are purchased from gifts made to the Smithsonian by a private foundation in California.
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As a final step in the dissemination process, it should be noted that calculations are now regularly performed by other groups, notably at NASA's Jet Propulsion Laboratory, of any remote possibilities that specific NEOs could collide with the Earth during the next century. Such calculations are fairly extensive but are quite automatic and entirely based on the observations organized and distributed by the Minor Planet Center. They are also routinely updated using the daily updates of NEO observations. Of course, it is almost always to be expected that, as further data are acquired, the impact possibilities completely disappear. That is, they will disappear unless the Earth is actually going to experience an impact—a point the dinosaurs 65 million years ago were unable to appreciate.
Most of the deliberate confirmatory and deliberate follow-up observations of NEOs, particularly those obtained in the U.S., are made by amateur astronomers. There are perhaps ten U.S. amateur groups and individuals (notably in Arizona, California, Kansas, New Mexico, Oregon, Tennessee and Wisconsin) who can be depended upon to make such observations, reliably and systematically. Although amateurs do still regularly discover main-belt asteroids (despite the dominance of the professional surveys), it is really quite rare for them to discover NEOs, but there have been NEO discoveries by amateurs in Arizona, and even Massachusetts, during the past two or three years. Amateurs tend to do better at discovering comets—some of which are technically NEOs—because these usually have a distinctive appearance and can often be found in the parts of the sky that are closer to the sun than are covered by the professional surveys. The Edgar Wilson Award for comet discoveries has therefore actually been made to between two and seven amateur astronomers each year. While the part of Pete Conrad Award for NEO discoveries will also be of some encouragement to recipients, the part awarded for follow-up observations should actually be more so. Perhaps the principal encouragement to amateurs nowadays is to make it possible for them to have ready access to the equipment they need to carry out their work. Government and private grants that have provided amateurs with electronic detectors during the past few years have been particularly effective. Of course, the Conrad and Wilson Awards could provide the same end result, but there is no guarantee. It should also be noted that there are better prospects for amateur discoveries in the southern hemisphere, because of the absence of professional surveys there.
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For more than a half-century after its inception in 1947, the Minor Planet Center functioned with just two scientific staff. By the time a third member was added in May 2000 the number of observations in its files had grown to 4.5 million (effectively from zero) and the number of objects with orbit determinations to 80,000—of which the 15,000 of guaranteed quality (i.e., the asteroids that have been given sequential numbers, and in some cases, names) represented a tenfold increase over the situation in 1947. The number of known NEOs in May 2000 was under 1000, with some 400 of them more than 1 km across. Now there are more than 15 million observations and very nearly 200,000 objects with orbit determinations—now almost 50,000 of these being numbered asteroids. There are now more than 2000 NEOs, of which some 640 are larger than 1 km. The Minor Planet Center's staff has been able to keep up with the influx, but only because of its extreme dedication. As already noted, a modest further increase in the size of the staff would be desirable—and it will be essential if the Center is to keep up with the exponential increase in data for much longer. Computing capabilities at the Minor Planet Center are very good, with new machines added from time to time, and since one staff member is particularly involved with upgrading the software, some augmentation of the staff would also allow that member to concentrate more on this important task.
Although the official NASA mandate is to concentrate on NEOs that are 1 km across or larger, there are already data on many smaller NEOs in the files. There are some 1800 NEOs down to 200–300 meters (this number increasing by around 400 annually), out of perhaps 40,000 that must exist. Even with the present observational and computational capabilities, the inventory of known objects could be a substantial fraction of the estimated total after several more decades (particularly if one also considers redefining NEOs to include only those objects that pass somewhat closer to the sun than the present limit of some 120 million miles, for asteroids at that minimum distance cannot possibly be a significant threat to the Earth, at 91–95 million miles, for millions of years into the future). Making use of larger telescopes could allow 200-meter NEOs to be sampled to a completeness level approaching 90 percent after just a decade or two. (One worry about some of the proposed telescopes is that they are really designed for surveys of objects outside the solar system, and therefore only one image of a particular field would be obtained on a given night. As noted at the beginning of this testimony, the apparent motion of an object over an hour or so is essential for recognizing NEOs. It is also essential for linking data on a particular object from one night to another.) Given the expected increases in computing capabilities during that time, the Minor Planet Center could keep up with this (as it has clearly done before), again provided that there are sufficient staff members. It should be remembered that NEO observation, with the need for confirmation and follow-up, is necessarily an international activity, for the simple reason that it is not possible to observe the whole sky from the U.S., and it is not possible to observe the reachable sky at all times. The Minor Planet Center, with its international connections, is well-equipped to attend to this point.
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If it is decided that it would ultimately be desirable to extend the NEO searches down to a size limit of, say, 50 meters, with perhaps a million objects to find, the whole perspective does change quite significantly, and it would clearly then become efficient to make the searches from space-based telescopes. Data-management requirements would also become much more intensive, with a clear need for round-the-clock attention. While this might be the ultimate goal, the more obvious immediate step is to go down to the 200–300-meter level, as was discussed in the comprehensive Task Force Report on NEOs to the U.K. government in 2000. This would be a logical and effective transition that could be accomplished quite rapidly, and the increased data-management requirements could be reasonably addressed, as discussed in the previous paragraph.
BIOGRAPHY FOR BRIAN G. MARSDEN
Dr. Brian G. Marsden is an astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, and specializes in celestial mechanics and astrometry, with particular application to the study of comets, asteroids and natural satellites. He was born in Cambridge, England, and his undergraduate education was at Oxford University. He received his Ph.D. degree from Yale University, his dissertation being concerned with the orbits of the Galilean satellites of Jupiter. He has examined in particular the nongravitational forces that affect the motions of comets, has extensively studied the Kreutz group of sungrazing comets and is an authority on procedures for deriving useful orbital information from minimal information—something that is proving very applicable to the numerous transneptunian objects discovered in recent years. He has successfully predicted the return of several lost comets and asteroids, notably the 1992 return of Comet Swift-Tuttle, which has the longest period of any comet ever successfully predicted. In 2002 he recognized another group of now more than a dozen near-sun comets that is termed the Marsden Group. He is the author of the standard Catalogue of Cometary Orbits, fourteen editions of which have been published since 1972. He was director of the International Astronomical Union's Central Bureau for Astronomical Telegrams from 1968 to 2000, and in this capacity has been responsible for the timely dissemination of information about transient astronomical objects and events; since 1978 he has also directed the IAU's Minor Planet Center, which issues various printed and electronic publications, including monthly batches of Minor Planet Circulars with positional observations, orbital elements and related information about comets and asteroids. From 1987 to 2002 he was Associate Director for Planetary Sciences at the Harvard-Smithsonian Center for Astrophysics. He has also served as Chairman of the American Astronomical Society's Division on Dynamical Astronomy (1976–1978) and as President of the IAU's Commission on the Positions and Motions of Minor Planets, Comets and Satellites (1976–1979); he was on the Board of Directors of The Spaceguard Foundation (1996–2002), serving in particular as Vice President during 1998–2002; and he is currently President of the IAU's Commission on Astronomical Telegrams. In 1974 the minor planet (1877) was named in his honor. Among his several other honors are the Goodacre Medal of the British Astronomical Association in 1979, the University of Arizona's Van Biesbroeck Award for services to astronomy in 1989, the Camus-Waitz Medal of the Société Astronomique de France in 1993, the AAS Brouwer Award for research in dynamical astronomy in 1995 and the Lacchini Prize of the Unione Astrofili Italiani in 2001.
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Mr. WELDON [presiding]. Thank you, Dr. Marsden. Our next witness is Air Force Brigadier General Simon ''Pete'' Worden. He is here today not as a representative of the Air Force, but rather to present his views on the NEO issue. He will discuss current and possibly future roles of the Air Force in conducting surveys of Near-Earth Objects.
Welcome back. It is good to have you before the Committee. You are recognized for five minutes, General.
STATEMENT OF BRIGADIER GENERAL SIMON P. WORDEN, UNITED STATES AIR FORCE
Brigadier General WORDEN. Thank you, Mr. Chairman and Distinguished Members. I am delighted to be here. And as you point out, the Department of Defense does not have a position as of yet on this issue. That is why I am here as a—as both a space scientist and as an expert on military space operations. And I would also like to commend Chairman Rohrabacher and Congress for their recent legislation in honoring an old friend. I would like to count him as a fellow visionary, Pete Conrad. I have to note I had a rather scary ride with Pete out to the DCX Delta Clipper first flight at White Sands in his, what I call, ground-based orbital vehicle. And although I had my eyes closed during most of this flight, we discussed future targets for man flights, and asteroids were high on the list. So this is a topic of long-standing interest to me.
Now over the past few years, I have been sort of a proponent of looking very carefully at the threat. And I note, as the previous speakers have discussed, the large objects, the objects that are five, ten miles in diameter, are certainly a very important object to study. However, when I go to my leadership and talk about something that happens only every hundred million years, they think that is something we can defer probably for this year's budget.
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But I will note that there are some other threats that are beginning to concern a lot of us. First is very, very small objects, a few maybe ten feet in diameter. We see about 30 of these that hit the upper atmosphere a year. Now they explode in the upper atmosphere, so they are no threat to people on the ground, but they release energy levels equivalent to a nuclear weapon, a few kilotons in most cases.
An event occurred in the 6th of June that raised the concern on a lot of folks. Over the Mediterranean, we observed with our satellites, early warning satellites, something that released about 20 to 30 kilotons of energy, larger than the Hiroshima atomic bomb. Our concern was had this event occurred over India or Pakistan, which were at a nuclear crisis at that time, it could have triggered a—the nuclear catastrophe that we have avoided for over a half a century. So one of our concerns here is that this might be a potential topic for shared early warning. We are unique in having sensors in the United States that can determine whether these are nuclear weapons or missiles launched or a reentering object or an asteroid. But that is the first real threat we have some concern with.
Other threats from natural objects, several years ago we had what was called a meteor storm, the Leonids, which are the debris of an old comet. Every 33 years, this particular meteor storm recurs. In the 60's, it was a very large storm. There were some predictions that had it been as bad as it was then, we could have lost many of our satellites. We might have lost most of the GPS constellation. So there was a second concern of natural objects that impact the Department of Defense.
The third has been discussed. Many of these smaller objects have the potential of nuclear levels of damage. We did see, in 1996, a hundred-kiloton detonation over Greenland. That would have been enough to have caused some levels of damage on the ground. Of course, most people are aware in 1908; there was a megaton level event in Tunguska in Siberia. These are relatively small objects, from a few tens of feet to a few hundred feet in diameter. This, of course, is beyond our current capability to survey these objects, but it is something, in my opinion as a scientist, we ought to consider in the future.
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Now I think the current DOD role is to support NASA in terms of their Survey. As was noted, a number of our telescopes and equipment had been very helpful there, but there are some—there are several things that we could do in the future that might assist. We are beginning to do research on large-format detectors, Charged Coupled Devices. And we are considering potentially building a prototype of our next generation satellite tracking system that could survey all of the sky. This could serve, perhaps, the dual use as both a pathfinder for future national systems and could even itself serve to track asteroids as well as satellites.
Second, we currently have a single satellite in orbit that tracks objects in space called the MSX satellite. It is, in my opinion, in our experience, superior to ground-based systems. We believe that in the future, we are going to upgrade with a network of these satellites that could also serve as an early warning system, potentially, for some of these smaller objects, giving us, perhaps, at least hours, if not days, of warning.
Finally, the Department of Defense is doing a lot of work on what are called ''microsatellites''. These are things that weigh 100 to 200 pounds that may only cost a few million dollars to build. We think that technology has a lot of application. We—in my opinion, we need to follow up with scientific programs to these military systems. I personally strongly endorse the large telescope that was discussed here a few moments ago.
I am also delighted that amateurs are looking at the sky. They help a lot in a lot of ways. In fact, we have occasionally turned to them to track satellites. And I would also note that some of them aren't so amateur. I heard a proposal for a 60-inch telescope here from an amateur in Tucson a few days ago.
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For the short-term, what we would propose doing in the Air Force is to consider a warning center that would look at tracking objects, not just as we do today that are in Earth orbit, but also maintaining a situational awareness on objects in solar orbit, which are—include the NEOs, and making an assessment if these present any threat with a variety of sensors and making that data available to the scientific and national community. Now this would require us to have assigned a new mission, but I think that is one that could be discussed in the future and may potentially be quite promising.
Now last, I would just like to say a word on mitigation, which is something that I think I probably share an opinion with the rest of the Committee here that it is something we should probably wait to getting real serious about until threats are discovered. But in the meantime, this technology I mentioned in microsatellites could potentially be dual use that as we do experiments in the Department of Defense in the next few years, we could work with the scientific community to do some of these technology experiments that actually would go and visit some Near-Earth Asteroids.
A few years ago, I was privileged to run the technology programs in the Missile Defense Program. We did a dual use mission in 1994 called ''Clementine,'' which went to the moon and was one of the first indication of ice being in the poles of the moon. Follow-on experiments like that one or something that we could certainly consider. If these are successful, we could mount numerous missions for a few million dollars each, a much lower cost than current exploration missions, that could do the detailed physical characterization of a wide variety of asteroids.
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In summary, I guess I would like to say that I believe the Department of Defense has some considerable capabilities and technology that could assist here. I believe there is a real threat to both military operations and much broader civilian concerns. I think the U.S. military brings a lot of expertise and I would hope that as we define our national program here that we can integrate some of the capabilities as we already have. This is an item of discussion with NASA and the Department of Defense. One week from yesterday there is a partnership council with NASA and the DOD where this particular topic is on the agenda. Thank you.
[The prepared statement of Brigadier General Worden follows:]
PREPARED STATEMENT OF BRIGADIER GENERAL SIMON P. WORDEN
Chairman Rohrabacher, Congressman Gordon, and Members of the Committee:
Interest in the threat caused by natural objects (''Near-Earth Objects'' or NEOs) impacting the Earth or its atmosphere is growing. High-level commissions have met to consider the problem in such places as the United Kingdom. In the United States, NASA has devoted a few million dollars per year to studying the phenomenon. But no concrete plan exists to address the overall NEO problem.
The U.S. Department of Defense (DOD) has not perceived the NEO issue as pressing. However, DOD is assisting NASA in studying the problem. It has been DOD-developed technology, particularly in the space surveillance area, which has obtained the bulk of data we currently have on NEOs.
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I have been asked to address my perspectives on the NEO threat and what should be done about it. I make the following comments not as a representative of the U.S. DOD, but rather as a scientist who has studied NEOs, and as a space expert familiar with the technologies that might be applicable to the problem.
THE THREAT
Two and a half months ago, Pakistan and India were at full alert and poised for a large-scale war, which both sides appeared ready to escalate into nuclear war. The situation has defused—for now. Most of the world knew about this situation and watched and worried. But few know of an event over the Mediterranean on June 6th of this year that could have had a serious bearing on that outcome. U.S. early warning satellites detected a flash that indicated an energy release comparable to the Hiroshima burst. We see about 30 such bursts per year, but this one was one of the largest we have ever seen. The event was caused by the impact of a small asteroid, probably about 5–10 meters in diameter, on the Earth's atmosphere. Had you been situated on a vessel directly underneath, the intensely bright flash would have been followed by a shock wave that would have rattled the entire ship, and possibly caused minor damage.
The event of this June received little or no notice as far as we can tell. However, if it had occurred at the same latitude just a few hours earlier, the result on human affairs might have been much worse. Imagine that the bright flash accompanied by a damaging shock wave had occurred over India or Pakistan. To our knowledge, neither of those nations have the sophisticated sensors that can determine the difference between a natural NEO impact and a nuclear detonation. The resulting panic in the nuclear-armed and hair-triggered opposing forces could have been the spark that ignited a nuclear horror we have avoided for over a half century.
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I've just relayed one aspect of NEOs that should worry us all. As more and more nations acquire nuclear weapons—nations without the sophisticated controls and capabilities built up by the United States over the 40 years of Cold War—we should ensure the 30-odd yearly impacts on the upper atmosphere are well understood by all to be just what they are.
A few years ago those of us charged with protecting this nation's vital space systems, such as the Global Positioning System, became aware of another aspect of the NEO problem. This was the Leonid meteor storm. This particular storm occurs every 33 years. It is caused by the debris from a different type of NEO—a comet. When the Earth passes through the path of a comet, it can encounter the dust thrown off by that comet through its progressive passes by the sun. This dust is visible on the Earth as a spectacular meteor storm. But our satellites in space can experience the storm as a series of intensely damaging micrometeorite strikes. We know about many of these storms and we have figured out their parent comet sources. But there are some storms arising from comets that are too dim for us to see that can produce ''surprise'' events. One of these meteor storms has the potential of knocking out some or even most of our Earth-orbiting systems. If just one random satellite failure in a pager communications satellite a few years ago seriously disrupted our lives, imagine what losing dozens of satellites could do.
Most people know of the Tunguska NEO strike in Siberia in 1908. An object probably less than 100 meters in diameter struck Siberia, releasing equivalent energy of up to 10 megatons. Many experts believe there were two other smaller events later in the century—one in Central Asia in the 1940s and one in the Amazon in the 1930s. In 1996, our satellite sensors detected a burst over Greenland of approximately 100 kiloton yield. Had any of these struck over a populated area, thousands and perhaps hundreds of thousands might have perished. Experts now tell us that an even worse catastrophe than a land impact of a Tunguska-size event would be an ocean impact near a heavily populated shore. The resulting tidal wave could inundate shorelines for hundreds of miles and potentially kill millions. There are hundreds of thousands of objects the size of the Tunguska NEO that come near the Earth. We know the orbits of just a few.
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Finally, just about everyone knows of the ''dinosaur killer'' asteroids. These are objects, a few kilometers across, that strike on time scales of tens of millions of years. While the prospect of such strikes grabs people's attention and make great catastrophe movies, too much focus on these events has, in my opinion, been counterproductive. Most leaders in the United States or elsewhere believe there are more pressing problems than something that may only happen every 50–100 million years. I advocate we focus our energies on the smaller, more immediate threats. This is not to say we do not worry about the large threats. However, I'm reasonably confidant we will find almost all large objects within a decade or less. If we find any that seem to be on a near-term collision course—which I believe unlikely—we can deal with the problem then.
WHAT SHOULD WE DO?
First and foremost, when an object strikes the Earth, we must know exactly what it is and where it hit. Fortunately, our early warning satellites already do a good job of this task. Our next generation system, the Space-Based Infrared System, will be even better. The primary difficulty is that this data is also used for vital early warning purposes and its detailed performance is classified. However, in recent years, the U.S. DOD has been working to provide extracts of this data to nations potentially under missile attack with cooperative programs known as ''Shared Early Warning.'' Some data about asteroid strikes have also been released to the scientific community. Unfortunately, it takes several weeks for this data to be released. I believe we should work to assess and release this data as soon as possible to all interested parties, while ensuring sensitive performance data is safeguarded.
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We have studied what a NEO warning center might look like. I believe adding a modest number of people, probably less than 10, to current early warning centers and supporting staffs within Cheyenne Mountain could form the basis of a Natural Impact Warning Clearinghouse.
Perhaps the most urgent mid-term task has already begun. This is the systematic observation and cataloging of nearly all potentially threatening NEOs. We are probably about halfway through cataloging ''large'' NEOs (greater than a kilometer in diameter). It is interesting to note the most effective sensor has been the MIT Lincoln Lab LINEAR facility in New Mexico, which is a test bed for the next generation of military ground-based space surveillance sensors. But this ground-based system, however effective, can only address the ''large,'' highly unlikely threats. We find out every few weeks about ''modest'' asteroids a few hundred meters in diameter. Most sail by the Earth unnoticed until they have passed. In recent months, the object 2002 MN had just this sort of near miss—passing only a few tens of thousands of kilometers from the Earth. Ground-based systems such as LINEAR are unable to detect one of the most potentially damaging classes of objects, such as comets that come at us from the direction of the sun. New space-surveillance systems capable of scanning the entire sky every few days are what is needed.
New technologies for space-based and ground-based surveys of the entire space near the Earth are available. These technologies could enable us to completely catalog and warn of objects as small as the Tunguska meteor (less than 100 meters in diameter). The LINEAR system is limited primarily by the size of its main optics—about one meter in diameter. By building a set of three-meter diameter telescopes equipped with new large-format Charged Coupled Devices, the entire sky could be scanned every few weeks and the follow-up observations necessary to accurately define orbits, particularly for small objects, could be done.
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The most promising systems for wide-area survey—particularly to observe close to the sun to see objects coming up from that direction—are space-based surveillance systems. Today the only space-based space surveillance system is the DOD's Midcourse Space Experiment (MSX) satellite. This was a late 1990s missile defense test satellite, and most of its sensors have now failed. However one small package weighing about 20 kg and called the Space-Based Visible sensor is able to search and track satellites in geosynchronous orbit (GEO) using visible light. This has been a phenomenally successful mission, having lowered the number of ''lost'' objects in GEO orbit by over a factor of two. MSX is not used for imaging asteroids, but a similar sensor could be. The Canadian Space Agency, in concert with the Canadian Department of National Defense, is considering a ''microsatellite'' experiment with the entire satellite and payload weighing just 60 kg. This Near-Earth Surveillance System would track satellites in GEO orbit, as MSX does today. However, it would also be able to search the critical region near the sun for NEOs that would be missed by conventional surveys.
The U.S. DOD is planning a constellation of somewhat larger satellites to perform our basic satellite-tracking mission. Today our ground-based radars and telescopes, and even MSX, only track objects that we already know about. These systems are not true outer-space search instruments as the LINEAR system is. However, the future military space surveillance system would be able to search the entire sky. As an almost ''free'' by-product, it could also perform the NEO search mission. Larger aperture ground-based systems could then be used to follow up to get accurate orbits for the NEOs discovered by the space-based search satellites. Again, I believe there is considerable synergy between national security requirements related to man-made satellites and global security requirements related to NEO impacts.
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Regardless of how well we know NEO orbits and can predict their impacts, the fact remains that today, we have insufficient information to contemplate mitigating an impact. We do not know the internal structure of these objects. Indeed, we have reason to believe that many, if not most, are more in the nature of ''rubble piles'' than coherent objects. This structure suggests that any effort to ''push'' or divert a NEO might simply fragment it, which could potentially turn a single dangerous asteroid into hundreds of objects that could damage a much larger area.
What is needed are in situ measurements across the many classes of NEOs, including asteroids and comets. This is particularly important in the case of small (100 meter) class objects of the type we would most likely be called upon to divert. Until recently, missions to gather these data would have taken up to a decade to develop and launch and cost hundreds of millions of dollars. However, the situation looks much better with the emergence of so-called ''microsatellites,'' which weigh between 50–200 kg and can be launched as almost ''free'' auxiliary payloads on large commercial and other flights to GEO orbit. These missions can be prepared in one to two years for about $5–10M, and launched for a few million dollars as an auxiliary payload. I believe such auxiliary accommodation is a standard feature on the European Ariane launches, and could be considered here in the United States on our new Evolved Expendable Launch Vehicles.
With a capable microsatellite with several kilometers per second ''delta-V'' (maneuver capacity) launched into a GEO transfer orbit (the standard initial launch orbit for placing systems into GEO), the satellite could easily reach some NEOs and perform in situ research. This could include sample return, direct impact to determine the internal structure and the potential to move a small object. Indeed, NASA is planning several small satellite missions. The key point here, however, is that with missions costing $10M each, we can sample many types of NEOs in the next decade or so to gain a full understanding of the type of objects we face.
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There is an interesting concept to consider. If we can find the right small object in the right orbit, we might be able to nudge it into an orbit ''captured'' by the Earth. This would make a NEO a second natural satellite of Earth. Indeed, there is at least one NEO that is close to being trapped by the Earth now, 2002 AA29. If such an object were more permanently in Earth orbit, it could be more closely studied and might form the basis for long-term commercial exploitation of space. Moreover, a very interesting manned space flight mission after the Space Station could be to an asteroid; maybe even one we put into Earth's gravity sphere.
One important aspect of NEO mitigation is often overlooked. Most experts prefer to focus on the glamorous ''mitigation'' technologies—diverting or destroying objects. In fact, as the U.S. military knows well the harder part is what we call ''command and control.'' Who will determine if a threat exists? Who will decide on the course of action? Who will direct the mission and determine when mission changes are to be made? Who will determine if the mission was successful? There are many more questions.
The U.S. military has long struggled with these command and control issues that now confront the NEO community. Earlier, I noted a concept of operations for the first step in NEO mitigation—a Natural Impact Warning Clearinghouse. I believe this command and control operation could catalog and provide credible warning information on future NEO impact problems, as well as rapidly provide information on the nature of an impact.
INTERNATIONAL ISSUES
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Many have suggested any NEO impact mitigation should be an international operation. In my opinion, the United States should proceed carefully in this area. International space programs, such as the International Space Station, fill many functions. A NEO mitigation program would have only one objective. In my view, a single responsible nation would have the best chance of a successful NEO mitigation mission. The responsible nation would not need to worry about giving up national security sensitive information and technology as it would build and control the entire mission itself. As I have pointed out, the means to identify threats and mitigate them overlap with other national security objectives.
It does, however, make sense that the data gathered from surveys and in situ measurements be shared among all. This would maximize the possibility the nation best-positioned to perform a mitigation mission would come forward. One of the first tasks of the Natural Impact Warning Clearinghouse noted above could be to collect and provide a distribution point for such data.
ROLES OF THE U.S. MILITARY AND NASA
Currently, NASA has been assigned the task of addressing some NEO issues. The U.S. DOD has been asked to assist this effort. However, the U.S. DOD has not been assigned tasks, nor has any item relating to NEOs been included in military operational requirements. I believe one option would be for the U.S. DOD to assume the role of collecting available data and assessing what, if any, threat might exist from possible NEO collisions of all sizes. This does not mean other groups, in particular the international scientific community, should not continue their independent efforts. However, the U.S. DOD is likely, for the foreseeable future, to have most of the required sensors to do this job. Moreover, in my view, the U.S. DOD has the discipline and continuity to ensure consistent, long-term focus for this important job. As a consequence of this function, the U.S. DOD might collect a large quantity of important scientific data. To the degree that the vast bulk of this has no military security implications, it could be released to the international scientific community.
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In addition, I believe NASA should continue the scientific task of assessing the nature of NEOs. Performing the necessary scientific studies, including missions to NEOs to gather data, is among NASA's responsibilities. Like the 1994 U.S. DOD/NASA Clementine probe, these missions could serve as important technological demonstrations for the U.S. DOD, and might be conducted jointly with NASA.
Should a threatening NEO be discovered, it is my opinion the U.S. DOD could offer much toward mitigating the threat. Of course, with a funded and focused surveillance program for cataloging and scientific study as outlined above, we should have ample time to debate this issue before it becomes critical.
SUMMARY
NEO mitigation is a topic whose time has come. I believe various aspects related to NEO impacts, including the possibility that an impact would be misidentified as a nuclear attack, are critical national and international security issues. The focus of NEO mitigation efforts—in finding and tracking them, and in exploring and moving some—should shift to smaller objects. The near-term threats are much more likely to come from these ''small'' objects (100 meters in diameter or so) and we might be able to divert such objects without recourse to nuclear devices.
After a suitable class of NEOs is found, microsatellite missions to explore and perhaps perform test divert operations could be considered. The technologies for low-cost NEO missions exist today.
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The necessary command and control, sensor and space operations technologies and equipment are all ''dual use'' to the military. In my view, it stands to reason that strong military involvement should be considered in a national and international NEO program.
PERSPECTIVES ON THE NEAR-EARTH OBJECT (NEO) THREAT, SIMON P. WORDEN, BRIGADIER GENERAL, USAF, Deputy Director for Operations, United States Strategic Command, Peterson AFB, CO.
The opinions and concepts expressed are those of the author and do not necessarily represent the position of the Department of Defense or the United States Strategic Command.
81931g.eps
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Discussion
Mr. WELDON. I thank all of the witnesses for their very fascinating testimony and will now begin the question and answer phase of the hearing. And the gentleman from the State of Maryland, Mr. Bartlett, would you like to go first?
Mr. BARTLETT. I was privileged to be at Johns Hopkins University Applied Physics Lab when the satellite landed on Eros. I thought that provided an excellent opportunity in a very fascinating way to explain some mathematical things to people because I noted that that satellite went around Eros at about five miles an hour. At a slow trot I could have kept up with it, although what a great opportunity to explain to our young people some of these forces. I remember that Dan Goldin was very concerned that we were calling that a landing. He says it is a crash. But it is hard to crash at five miles an hour, isn't it? It turned out very well and it was still taking pictures after it landed. That is the bell for another vote, but we will have 10 minutes before we have to leave. I have a question. Since it is impossible to know what you don't know, how do you know you have cataloged 50 percent of them?
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NEO Survey
Dr. MORRISON. That is an excellent question of course and you don't know exactly. But it is a simple question of looking—when you do a survey of the sky, when you scan an area of the sky of how many of the objects that you discover are in fact already in your catalog. When you are about halfway through the survey, then for every new object you discover you'll rediscover another. When you are 90 percent of the way through then only 10 percent of the objects you think you are discovering will be new ones. And so as the survey progresses it automatically gives you a metric of how near you are coming to completion.
Mr. BARTLETT. I knew there was a good explanation. I just didn't know it. I really liked your analogy of fire insurance. Almost none of us expect that our home will burn tonight and yet you wouldn't sleep well—I am sure you would awaken your insurance agent from his bed to give you a binder on a policy if you didn't have fire insurance on your home. And you are exactly right. What we need as a nation, as a civilization really, is the equivalent of a fire insurance policy relative to any potential for future—I am not sure what that is but I am sure that we can come to grips with that. Now I know that tomorrow you have got to buy groceries and you have got to put your kid through school and you have got to make the car payment, but by golly, you still make the insurance premium payment on your home. And that is all that I ask for; possible contingencies like this that we have purchased for our people the equivalent of a fire insurance policy and we need to be moving in that direction. We have clearly not done that. We need first to access the risk. The probability is very low but the impact could be enormously high and that is exactly the kind of an event for which you buy insurance. And we haven't bought that insurance policy yet. The last question I have is how quickly could we determine this was not a nuclear explosion? One of you—General, you mentioned that. My concern is that if something like this happened in the right place and it took us too long to determine whether or not it was a nuclear explosion, there might be a few nuclear explosions as a consequence of our inability to define that and report it.
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Brigadier Gen. WORDEN. The exact—sir, the exact speed of these things are, of course, sensitive but it is in matters of less than a minute.
Differentiating Between NEOs and Nuclear Explosions
Mr. BARTLETT. That we would know the difference?
Brigadier Gen. WORDEN. Yes, sir.
Mr. BARTLETT. Then why your concerns if it happened over India or Pakistan it might have been a problem?
Brigadier Gen. WORDEN. Exactly. The issue is, is that the United States is now unique in the world in having sensors that can determine the difference.
Mr. BARTLETT. Okay. You said they don't have the sensors and so we need to make those sensors available on a worldwide basis to complete this.
Brigadier Gen. WORDEN. I believe we could do that if assigned to do that. Today we share early warning data on missile launches, for example. And it would be fairly easy to share some of those data but it has to be something that is tasked and go through a—we have a really complicated process called the Unified Command Plan, which has mission statements in it. And if this was something that the United States Government wanted us to do, it is a straightforward thing to ask us to take care of it.
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NEO Near-Misses
Mr. BARTLETT. Just one last thing. In the recent past we have had two of these that we have only observed after they passed us and in terms of celestial mechanics they just missed us by a hair breadth. Didn't they? How sanguine are you that with that experience say we are going to be able in the future to identify those that are coming at us?
Dr. MORRISON. I would like—that is a good question that I would like to speak to for just a moment. The purpose of these surveys is never to define an object on its final plunge toward Earth. Among other things, it would be too late to do anything about it. We really want to take a complete survey around the Earth and add them to our survey one at a time, calculate their orbits and determine if they pose a future risk.
Mr. BARTLETT. How did we miss those two?
Dr. MORRISON. For that purpose we didn't miss them. We found them.
Mr. BARTLETT. But after they went by.
Dr. MORRISON. Didn't matter. They didn't hit us. Did they?
Mr. BARTLETT. Barely.
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Dr. MORRISON. They were added to the catalog and there is no extra points for getting it on the way in, no demerits for getting it on the way out. Those things were going by at this rate all along. It is only now that we have the telescopes and the survey to find them. And we are finding them and every one that is added to our catalog is a success of the mission.
Dr. MARSDEN. They were very small objects. The one in June that was found three days after it passed was only 50 meters, 70 meters across. So it is not in the current mandate of the one kilometer.
Chairman ROHRABACHER. And what kind of damage could that have done had it hit——
Dr. MARSDEN. Well, it wouldn't be——
Chairman ROHRABACHER [continuing]. Southern California?
Dr. MARSDEN. Similar to what happened over Tunguska in 1908.
Chairman ROHRABACHER. You mean killing everybody?
Dr. MARSDEN. Yes. I am afraid so.
Chairman ROHRABACHER. Oh, all right. Well, I'm glad——
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Dr. MARSDEN. Maybe you'll be here in Washington.
Chairman ROHRABACHER. I was very concerned to hear——
Brigadier Gen. WORDEN. Sir, if I might add that it is possible to find these things in the way in but it is a different kind of system. It is much similar to the kind of systems we are looking at in the next decade to track all of the satellites in Earth orbit so that we kind of know where they are within a few hours. If we have that survey system and it is surveying the right area we could pick these things up on their way in but it is a different kind of system than the survey that the scientist need.
Mr. BARTLETT. Thank you very much.
Chairman ROHRABACHER. Thank you. We have a vote on and—two votes. So I am sorry. I apologize for missing your testimony. I was down again. We have a hearing on the Iraq legislation that is going through International Relations Subcommittee in which I am a member. I am not—it doesn't give me much satisfaction to know that because it missed us we don't have to worry about it, something that could, you know, just kill everybody in Southern California. But we will get back to this testimony after we vote. So it should be probably around 15 minutes but we will reconvene immediately after the—well, actually not after the last vote, but we should vote in two votes. We should come back, vote and immediately come back and so this should be about a 15-minute recess. Subcommittee is in recess.
[Recess]
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Chairman ROHRABACHER. I call this meeting of the Space and Aeronautic Subcommittee to order again. And again, thank you to the witnesses for your provocative testimony. I have got some questions of my own but I am going to tip my hat to Bart Gordon here because he has been here for the whole hearing. And I am going to try to catch up on some of the testimony of the two witnesses that I missed while going down to International Relations Committee and working on the Saddam Hussein program. So Bart, you may proceed.
Mr. GORDON. Thank you, Mr. Chairman. First let me say that I was pleased to learn through the testimony that when we find asteroids smaller than one kilometer you don't just wad it up and throw in the basket. And doctor, while we look forward to your report in June, I hope you will be making this committee aware of it, it is clearly somewhere we have to draw a line and determine what can be done cost effectively balanced with the importance. But hopefully, there can be some synergy and some economy of maybe reducing that, and we will be anxious to hear your report. Now I have got a couple of questions. Dr. Morrison, on July 9, 2002 a two-kilometer near-Earth asteroid was discovered. That announcement was followed by a number of media reports indicating that it would be on a collision course with the Earth in the year 2019. Those reports were later discounted. This is only the latest in a series of false alarms involving near-Earth asteroids. What went wrong and what should be done to reduce or eliminate the number of future false alarms?
False Alarms
Dr. MORRISON. Mr. Gordon, that is a very difficult question because we live in an open society and we share this information, and we neither can—nor should—try to control what the press reports. Those original stories that said that asteroid was on a collision course with Earth are from my perspective just flat-out wrong. They were incorrect. And I think the best we can do is be open, post the true situation on our web sites, speak with the press when they ask and let the situation take care of itself. We have tried in the past to say no. We won't say anything until we have verified, until we have gone through more testing and so on. But in fact, these stories get out and I think that we just have to live with the fact that some of those reporters are inaccurate.
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Mr. GORDON. So it was inaccurate from the start or was there some basis early on where you said this could happen but we need to check some more on it? What was——
Dr. MORRISON. The original calculations were that there was a roughly one in 100,000, perhaps one in 60,000 chance based on a preliminary orbit, of an impact. Now to say that is equivalent to it is on a course to hit the Earth is sort of like saying if you bought a lottery ticket, as you walked out of the lottery shop, the headline would say you won. Well, just the fact that you had some chance of winning isn't equivalent to winning.
Mr. GORDON. Thank you, sir. I do think—yes. Did you want to——
Dr. MARSDEN. Just if I might elaborate on this a bit more, I think this is one of the good things that has happened during the last few years that—what happens with these things, they come close to the—we know they can come close to the Earth. On occasion, they do come close to the Earth, but there is no chance of a hit. But the Earth has a gravitational influence on them so that you don't really know what they are going to do subsequently and it is found in many of these instances that there is a non-zero probability of an impact some time later in the century on another close pass. And the great thing that is happened during the last few years, since we had the event in 1998, where there was a close approach that set up things for a possible one in 50,000 impact a few years later. These calculations are being done routinely now by two groups in the world, one at JPL and one in Italy. They basically agree with each other, and this information is passed on to the astronomers who then know which objects to concentrate on. Let us make some more observations of this one so new calculations will be done to show that there is no chance of an impact any time in the future. But since—as our chairman has arranged for amateurs to be involved with this, I mean how can we get the information to all the amateurs other than by putting it in a public web page somewhere? I agree with Dave. The information has to be public. But if professional and amateur astronomers can get it, so can the press and it is the press then at that stage that sort of distort things with that kind of statement, it is on a collision course.
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Mr. GORDON. Well, fortunately the Chairman didn't sell his house on the last occasion and it wasn't widespread panic. But I think that there needs to be a sensitivity to this and any plan on getting back into the press when these sort of things happen. You need to—sort of like corporate management. You need to have a plan when something goes awry. Did you want to—because I want to get your second question before——
Dr. BURNS. Yes. I did want to comment because I think it is a general problem, of course, of when there is a small probability event occurring, the public doesn't appreciate what is meant by a small probability event, I think, for one. And secondly, it is the way that science operates. Science operates by making a hypothesis, improving on that hypothesis by making additional observations and finding out whether or not it is true.
NASA's Role in Follow-on Research and Categorization
Mr. GORDON. But I think you can get in the media quickly as we try to talk about it in the same cycle with defining small probability. I think that if I was a listener or watcher to the media and someone said there was a small probability of being hit by an asteroid, I would be a little concerned. You know, if they said it was one in 100,000, I would be less concerned. And so I think that, you know, that your responsibility is to quickly get in and define those terms. Now move on if that is okay? Okay. Dr. Weiler, in his testimony, made two straightforward statements—in his written testimony. One was we—NASA that is—do not feel that we should play a role in any follow-on research and cataloging effort unless that effort needs to be specifically space-based in nature. And secondly, I feel it is premature to consider an extension of our current national program to include a complete search of smaller-sized NEOs. Now I would like each of you—the witnesses or anyone who would like to to comment on that statement. Or—why don't we start with—well, I don't know, Dr. Morrison. You may feel like you have a conflict there. So if you don't, then you go right ahead.
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Dr. MORRISON. I think one reason we are here this morning is that that sort of study and trade as to what the next step should be has not been completed and in fact has hardly been begun. And so I concur with Dr. Weiler in that we don't have that information yet and I think we should get it.
Mr. GORDON. But what about his feeling that NASA shouldn't be involved unless it is—there is a space-based platform, which I assume was his meaning?
Dr. MORRISON. As a scientist, I have no comment on that. That is not——
Mr. GORDON. Well, as a scientist you should have a comment. Maybe——
Dr. MORRISON. As to which agency does it? No, sir.
Mr. GORDON. Maybe as an employee of NASA, you might not. But as a scientist, you should have an opinion. Shouldn't you?
Dr. MORRISON. We are fortunate to have several agencies in the government with the capability of doing this sort of thing.
Mr. GORDON. All right. So you weren't much help to us, so anybody whose paycheck is not——
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Dr. BURNS. I am a free man here——
Mr. GORDON. Okay. Go right ahead.
Dr. BURNS [continuing]. In some ways, anyway. I go back to the original originating Act for NASA of 1958 that says that NASA, among other things, should acquire, construct, operate and maintain laboratories, research and testing sites and facilities. I also refer to the report from the Committee that was chaired by Norm Augustine that reported last year. And one of their final conclusions is that NASA should support critical ground-based facilities and scientifically enabling precursor and follow-up observations that are essential for the success of space missions. And I think that included under that will be observations of this whole panoply of objects that are coming in at us, but we need to know what these things are made up of. We need to know where they are. We need to know what our targets are, and we are not doing that today.
Mr. GORDON. Well, we need to know, but should NASA play a role——
Dr. BURNS. I think the way that you—that NASA——
Mr. GORDON [continuing]. Other than well, in a ground-base role.
Dr. BURNS. Yeah. I think they need to do whatever is necessary to run the best sort of missions possible.
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Mr. GORDON. Anyone else want to have—make——
Dr. MARSDEN. Well, as I——
Mr. GORDON. Then, Dr. Weiler, we will go back to you.
Dr. WEILER. Yes.
Dr. MARSDEN. As I said, I think it is very important that we go down to, let us say, 200-, 300-meter objects, however it is done. We could do it with the existing structure, but it will take a century. If that is satisfactory, let us do that. But I think most of us feel that it should be done a little bit more quickly than that and this is going to require bigger telescopes on the ground being used, such as——
Mr. GORDON. But my question really goes to some oversight aspects of this. You know, I don't have an opinion. I am just seeking your advice. And that is should NASA play a role only if it is space-based? In other words, should NASA not play a role if—in terms of a ground-based review?
Dr. MARSDEN. Well, I think it can play a role if it is ground-based. I don't know what other organization would do it.
Mr. GORDON. General, did you have—want to make a comment, then we will let Dr. Weiler——
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Brigadier Gen. WORDEN. Well, I mean, this, of course, gets into people's budgets so it is obviously very sensitive. I think that, you know, again as it is a consensus here, we need to go to smaller objects that requires newer systems. Some systems are being built. Some are proposed to be built. We have begun with the U.S. Government a dialog of, you know, what can we get out of existing things, what can we get out of planned things that various agencies are doing. And I think out of that will come—there is something that we are going to need, and it is probably a large telescope where they will be able to survey all of the sky, and we will discuss and argue who ought to do it, you know, and, you know, sometimes you pass the hat. And sometimes Congress tells us what to do. But I think as a summary, it needs to be done. We are discussing it between the various agencies and out of that will come some consensus, I hope. There is already begun, as Dr. Weiler pointed out, a study which people from the agencies concerned, from the Defense Department, from the National Science Foundation and from NASA are looking at this. And that is due out here in a few months. I am serving as the ex-officio DOD member on that. So I am confident we are going to get something there now. You will probably come to some impasse that, you know, we will go back and forth. But we have the mechanisms in place to solve that.
Mr. GORDON. Dr. Weiler, do you disagree with the Augustine report or you just don't want to pay for it?
Dr. WEILER. Mr. Gordon, let me address that question by addressing some of the other comments made. I appreciate the reference to the Space Act, etcetera. In my 25 years at NASA, I can honestly say that almost every ground-based facility ever built has been at one time or another justified to me as critical to my missions. And because my missions in space science are so broad you could justify every ground-based telescope on Earth as supporting the NASA Space Science mission. So that is a very delicate argument to get into, number one. Number two, in terms of do we feel a role, maybe I misled you. We are committed to Congress and we will continue to be committed to doing the ground-based survey and completing our commitment to you by 2008 of mapping all these asteroids to one kilometer or better. So we will be in this program and we are happy to be in this program. In terms of which agency is best suited to build ground-based telescopes, we are the Space Agency. I have 100 staff at NASA headquarters and a lot of people that work for me at various NASA centers. I choose those engineers and scientists because of their expertise.
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Mr. GORDON. Yeah, I don't mean to—the Chairman's making me hurry so I don't mean to shorten you, but—so if you don't—if it is not you, then who should do it?
Dr. WEILER. There are other Federal agencies that support——
Mr. GORDON. Who would you recommend?
Dr. WEILER. The National Science Foundation.
Mr. GORDON. Thank you.
Rationale for NEO Programs and Spending
Chairman ROHRABACHER. Let me just note that if we do understand that there is a danger here, and I don't believe that Bruce Willis is going to be contacted and save us at the last minute. I just have that sneaking suspicion that we as a people are going to have to get together and talk about it, as we are today, and put together a plan that might in some way help us avert a crisis situation. Because unlike the movies, there is no Bruce Willis out there, although General Worden certainly could pass for Bruce Willis, kind of. Okay. Because he has done so many exciting things in the past and accomplished——
Brigadier Gen. WORDEN. Do I get the pay raise, sir, that goes with that?
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Chairman ROHRABACHER. So anyway, let us note that I think it is up to us and that is why we are having this hearing to discuss this because there is not going to be any last-minute savior that comes out of nowhere if we face this challenge, and it is a challenge. But let us put it this way. It is not just—and I was hoping that today's discussion—I want to make sure I throw this into the discussion—would not be just about the danger of near-Earth objects, but perhaps that the near-Earth objects also represent an opportunity, which is why NASA should be the lead player in this whole scenario. Because yes, NASA should be involved with helping us confront the danger and in analyzing the danger, and in making sure that we are prepared with cooperation with other agencies to deflect the dangers so we are not hurt. But asteroids and comets of whatever size also pose an opportunity. I understand that there could be vast mineral wealth on these asteroids.
There is also scientific knowledge about creation and things that we need to know about, the development of the solar system on these asteroids. There is also—asteroids could potentially, and correct me if I am wrong, serve as a transportation system for some of our own scientific instruments, if they would be placed on asteroids and comets. Now am I way off base here? Someone want to kick—jump into that part of the discussion? And if these things do have this opportunity, certainly NASA, which is supposed to be our arm in space, should certainly be playing the major role. Well, now I understand that if NASA does, it is going to cost some money, and we might not be able to spend that same amount of money—sorry fellows—on global warming research. Now I am sorry about that. But I would think that maybe this is more important than that.
Dr. WEILER. Mr. Chairman, if I may that, is exactly——
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Chairman ROHRABACHER. Jump right in.
Dr. WEILER [continuing]. That is exactly why, I mean, we are—that is one of the reasons why we are spending a huge amount of money, $1.6 billion over the next five years, the run-out budget. And in the past to go out and not just categorize these things, which is a job that could be done from the ground. The bulk of our money by three or four or five orders of magnitude is being spent on finding out what these things are, what they are made of, and what the opportunities might be in——
Chairman ROHRABACHER. But in terms of charting this, we are only spending $4 million a year. Right? I mean, this $1.6 billion is, I believe—Dr. Marsden might—he is shaking his head yes. Is this not some sort of a little exaggeration as to how much money we are actually spending on this problem or challenge?
Dr. MARSDEN. I think I can add it up to about $3 million among the various search programs and what we at the Minor Planet Center have. And all the search programs work on a shoestring. Okay. We can bring in amateurs to help out. That doesn't cost anything.
Chairman ROHRABACHER. It costs $2000 for each of the three awards.
Dr. MARSDEN. Oh, sorry. Yes. It does cost—but is that the way we want to go? And some of the amateurs are very sophisticated, but I think more could be put into the survey programs.
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Air Force Capabilities Relating to NEOs
Chairman ROHRABACHER. And maybe more based on some of the hardware that we—not just ground-based, but also space-based hardware that would—I mean, this—the fact that NASA was able to land a vehicle on one of these asteroids was a tremendous accomplishment. And if they are able to do that, I mean, this is—really opens up a whole new universe of potential there, not only for the positive things, but for the negative things as well. General Worden, would it be the Air Force's job then if we determine something is heading in our direction to knock us out of its way? And if so, do we have the technology to do that today, knock it out of—onto another path?
Brigadier Gen. WORDEN. Well, what the Air Force's job is what we are assigned to do, so—and I am not in the business of writing orders to my own organization. So I mean——
Chairman ROHRABACHER. What about the capabilities——
Brigadier Gen. WORDEN. But the——
Chairman ROHRABACHER [continuing]. Before the orders are actually issued?
Brigadier Gen. WORDEN. If assigned, I would say the U.S. Scientific and Technical Committee can do that. That could be managed by the Department of Defense. It could be managed by NASA. It could be managed——
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Chairman ROHRABACHER. Do we have the technology——
Brigadier Gen. WORDEN. Yes.
Chairman ROHRABACHER [continuing]. Available today if a near-Earth object was heading toward the Earth that we——
Brigadier Gen. WORDEN. Well, I need to clarify that, you know, it depends how much warning you have. But——
Chairman ROHRABACHER. Let me give you a six-month or one-year warning.
Brigadier Gen. WORDEN. That is a very difficult job to do. I would think we would have a hard time with that.
Chairman ROHRABACHER. So if we have a one-year warning right now that these three objects that just barely missed us in the last couple of years, you wouldn't be able to deflect this thing if those things weren't just barely missing us, but were going to actually land on the Earth?
Brigadier Gen. WORDEN. I don't believe currently that we have the structure or the ability to do it. The technology might be there. I'd much prefer the 10-year one. We could do that.
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Chairman ROHRABACHER. Is there someone here that wants to make a guess on this? Dr. Burns.
NEO Mitigation Timetables
Dr. BURNS. I don't want to speculate on that, but I do want to point out that we don't know how to deflect anything. We know how to deflect objects that have known properties, but we don't know the properties of these things. There is a big difference between trying to push around a football and trying to push around a marshmallow.
Chairman ROHRABACHER. So we have got to study them to find out what they are all about, but also—I mean, you are saying that right now we don't know for sure that if we could just deflect it off its path——
Dr. BURNS. You know, if you go out and say you—one of the schemes that has been suggested is to set off explosions close to this thing. What if that explosion shatters the object in pieces and you get hit by buckshot rather than a shotgun shell?
Chairman ROHRABACHER. Right.
Dr. BURNS. Same thing.
Chairman ROHRABACHER. Right.
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Dr. BURNS. You know, there is the same amount of energy coming. I would like to——
Chairman ROHRABACHER. So there is a lot of uncertainties in this whole——
Dr. BURNS. Exactly.
Chairman ROHRABACHER [continuing]. Area?
Dr. BURNS. Exactly. And I'd like——
Chairman ROHRABACHER. And who is working on that? Who is working on this end of it?
Dr. BURNS. Buck Rogers, I think.
Chairman ROHRABACHER. There is nobody working on this?
Dr. WEILER. No. Well——
Chairman ROHRABACHER. Wait. Hold on. Wait a minute. There is an object in space. We just—three of them just missed the Earth. Is anybody working on if we end up finding one out there in two years out——
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Dr. BURNS. NASA is working on getting the properties by doing these space surveys.
Chairman ROHRABACHER. Doing properties, but what about doing something that would augment its course.
Brigadier Gen. WORDEN. Mr. Chairman.
Chairman ROHRABACHER. Yes, General.
Brigadier Gen. WORDEN. There is been a lot of work done on that.
Chairman ROHRABACHER. Okay.
Brigadier Gen. WORDEN. But it has not been official work by U.S. Government agencies. A lot of scientists and engineers have done proposals. There were a series of workshops in the early '90's on this topic. There have been workshops here recently on the topic.
Chairman ROHRABACHER. But we have not followed through in actually producing the technology.
Brigadier Gen. WORDEN. Well, the interesting thing, as my colleagues have pointed out, is that the summary of those is there are a whole variety of proposals of how one might mitigate them. The difficulty is, is that to choose among those, we all agree the first thing we need to do is find out what are the properties of these. Are they single objects, are they rubble piles, are they made out of, you know, stuff that is stuck together well, or——
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Chairman ROHRABACHER. I got you. We understand that. That is—but——
Brigadier Gen. WORDEN. If that is—so our conclusion of all of those workshops was—the next step is to get that information.
Chairman ROHRABACHER. But in reality what we are talking about is we are totally unprepared. If somebody would say tomorrow, oh, my gosh, this thing is coming in our direction. We didn't notice it for the last five years, but it is coming in our direction. It is going to be here in 18 months, we are now totally unprepared to try to do something that would have some modicum of success in deflecting it from hitting the Earth?
Dr. WEILER. Mr. Chairman, I think the answer to your question is probably yes if you only have that much notice. But I think it is important to point out that with the cataloging efforts, we are going to probably have more than that amount of notice.
Chairman ROHRABACHER. Right. But the point is we had three objects that went by and we didn't even know them at all. And again, it is not really a lot of satisfaction knowing well, gee, they missed us, so we don't really have to worry about it.
Dr. WEILER. But I want to—I don't want to leave you the impression that nothing is being done. I think it is—but we haven't talked about it a lot.
NEO Oceanic Impact Effects
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Chairman ROHRABACHER. Okay. Let me make it sort of—who is the one who talked about if the thing lands in the ocean and it really—was that you, Dr. Marsden?
Dr. MARSDEN. No. I think I——
Chairman ROHRABACHER. Okay. Dr. Marsden, let me ask you. If one of these smaller objects land in the ocean, what type of tidal wave does it generate, the smaller ones that you are talking about?
Dr. MARSDEN. 200 meters would be a pretty good tidal wave.
Dr. WEILER. Yeah. More than you would surf on.
Chairman ROHRABACHER. How big? No. How tall are we talking? What is a—is that—that is 500 feet or more?
Dr. MORRISON. Yeah. The calculations——
Dr. WEILER. More. Yeah.
Chairman ROHRABACHER. You are talking about like a 1000-foot wave?
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Dr. MARSDEN. Yes.
Dr. WEILER. Yes. It is a big one.
Chairman ROHRABACHER. Oh, only a 1000-foot wave. Only destroy New York or New Jersey or Southern California, San Francisco.
Dr. BURNS. I mean, that is the issue.
Chairman ROHRABACHER. How far as we talking about?
Dr. BURNS. Just runs over the whole place.
Chairman ROHRABACHER. And we are not prepared to stop that. All right.
Dr. MARSDEN. No. We are not.
Chairman ROHRABACHER. I got it.
Dr. MORRISON. But we are prepared to give you decades of warning.
Chairman ROHRABACHER. Well, we're just happy. Are we talking about a wave that is going to stop at Philadelphia or Kansas City? I mean, what—this is—you know what? This is really a serious matter and quite frankly it doesn't sound like to me that we have—and that is the purpose of this hearing, to draw some attention on it. And even though the chances are small, the price we would pay is horrendous. We have Mr. Weiner from New York who is now—I'll be happy to yield for.
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NEO Near-Misses (Cont.)
Mr. WEINER. Let me see if I can summarize. You have got down to near science something that is going to hit us in about 1000 years. Something that missed us by—we accidentally caught in the rearview mirror as it went by us, well, oops, sorry about that. It seems to me a little bit backwards in terms of the imperatives of the issue. We can't take testimony and hear witnesses and hear the members here say, well, here is why this is important because we could get hit with one of these suckers, and then say ''but we are going to start looking first at all the stuff in the vast universe before we get the stuff that is coming right at us.'' It seems to me, frankly, counter-intuitive that you would approach the problem in that way. Does 2002 NT-7 mean anything to any of the panel?
Dr. MARSDEN. Yes. This is the one we had in July.
Mr. WEINER. Right. The Lincoln—this is the description that was written for me. By no means am I an expert, although I did see Armageddon and I want my $8 back.
Dr. MARSDEN. Me too.
Mr. WEINER. The Lincoln Near-Earth Asteroid Research Center in New Mexico detected a 1.2 mile wide asteroid that it projects could hit the Earth as early as 2019.
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Dr. MARSDEN. That was what was——
Mr. WEINER. That is what we were talking about.
Dr. MARSDEN [continuing]. Done from—yes. That is the one.
Mr. WEINER. Okay. Now that is less than 20 years away. Okay. Now——
Dr. MARSDEN. It has gone away though. That——
Mr. WEINER. All gone?
Dr. MARSDEN. It is gone.
Mr. WEINER. Okay. So we don't have to worry about that one anymore?
Dr. MARSDEN. We don't have to worry about that one. Gone.
Mr. WEINER. It can't be liked sucked back into our gravitational——
Dr. MARSDEN. No, no. We are quite safe in 2019 from that object.
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Mr. WEINER. Thank you. One less thing that will keep me up at night. It strikes me, though, gentlemen, if I could that it seems that you all have trouble seeing things that come in the same direction as the sun.
Dr. MARSDEN. Yes. But at other times, they come from the other direction.
Mr. WEINER. I am not concerned about the ones that are going to miss me, sir. Those I am somehow—I am more sanguine about the ones that are going to miss me than the ones that we haven't seen that might hit me.
Dr. MARSDEN. Yes. But also——
Mr. WEINER. Yeah. Go ahead.
Dr. MARSDEN. Our surveys—the surveys will find everything that they can. They are doing a very good job on kilometer-sized objects at the moment. We are working down to smaller objects. These things are orbiting the sun, so if we can see them when they are far enough away in the dark
sky——
Mr. WEINER. Yeah. But I am asking you—I am no longer discussing the things that you see and you can testify here that——
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Dr. MARSDEN. Well——
Mr. WEINER [continuing]. You have got cataloged. I am concerned about the ones that frankly are more troublesome.
Dr. BURNS. If I might interrupt, the——
Mr. WEINER. Sure.
Dr. BURNS. The issue is that these objects, as they orbit, they go—not only go inside——
Mr. WEINER. Right. I understand.
Dr. BURNS [continuing]. They go out, but we can catch them on the way out, and they'll come back later on.
Mr. WEINER. No. I understand, you know. But it is one to say on the ball field I lost it in the sun. This is quite a different situation here I suspect.
Brigadier Gen. WORDEN. Sir, if you could—we do have a proposed experiment that is being looked at right now that would be potentially something that the Canadian Space Agency, the Canadian Department of National Defense and the U.S. DOD would sponsor. It is in the preliminary discussions that would be one of these little hundred pound satellites that would look—it is a prototype dual use that would look interior to the Earth's orbit, so it would be the first experiment to look at what is coming from that direction. It also, by the way, would survey Earth-orbiting satellites that—in the geo-synchronous belt——
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Mr. WEINER. Yeah.
Brigadier Gen. WORDEN [continuing]. Where the communication satellites are. That is an experiment that could be done later this decade. It is a potential one. There is technology that look interesting.
Mr. WEINER. Yeah.
Brigadier Gen. WORDEN. And that would be the first prototype of that. Now if——
Mr. WEINER. Well, I—but if I could just interrupt, you know, Dr. Morrison testified earlier that you don't give any more or less credit for things that you just missed, that you just saw, that you are trying to take the full picture. I have to tell you if we just missed one and we didn't know it was coming, I don't know why there isn't a greater amount of resource doing a forensic examination about what the heck we did wrong that we missed that one. Can you give me some sense of—I mean, I would hope that you are not just saying, well, this is one that is behind us; that you are saying, wow, how did we miss this one? Give me some ways that we miss stuff. Like to tell me how something—intuitively you would think when it get closer, it is bigger, and so tell me how one slips through the cracks like that or an example—perhaps using a specific example maybe you could help us understand that.
Dr. MORRISON. Well, first these that we are talking about since we did detect them did not slip through the cracks. They are now in our survey. Their orbits have been computed——
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Mr. WEINER. Dr. Morrison, can I interrupt——
Dr. MORRISON [continuing]. And they will——
Mr. WEINER [continuing]. On my point because it is clear you are not understanding the concern that now at least three members have expressed. There is a fundamental and extraordinarily, to me, obvious problem with saying that, oh, it is just the same as one that we cataloged that is 200 years away. No. It is a near miss as with all things. As with a near miss in a plane crash, I would hope that you would treat that one as a great deal greater importance to our body of knowledge than one that we did happen to catch up with 1000 years away. So are you telling me now that there isn't a full-scale, bells going off analysis when we do miss one slightly, and yes, you did miss it. Saying that you got it after it passed is wrong.
Dr. MORRISON. We miss a great——
Mr. WEINER. Let me just let Dr. Morrison take that.
Dr. MORRISON. We miss a great many. Until this survey began we missed them all. Now we are picking them up. That is major progress.
Mr. WEINER. This one was one that before you started looking that carefully——
Dr. MORRISON. Five years ago, it would have gone by and we would not have seen it. There are objects like that going by the Earth continuously.
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Mr. WEINER. Okay.
Dr. BURNS. The point is that we don't have a complete survey. I mean, that is what we are here for, trying to say that there should be a complete survey.
Mr. WEINER. No. But——
Dr. BURNS. We are looking at small portions of the sky for small periods of time.
Mr. WEINER. I see. So you can't look at close, little less close, a little less close, a little less close?
Dr. BURNS. Right.
Mr. WEINER. You can't do it that way?
Dr. BURNS. These come winging past, and in some sense, I mean, you are certainly right when you say if it is closer it is brighter. But remember, it also moves faster, and so it can whip through your telescope before you have a chance of seeing it.
Brigadier Gen. WORDEN. Well, I think——
Dr. BURNS. Having small portions——
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Brigadier Gen. WORDEN [continuing]. The key is how these telescopes work. They have a very small, you know—it is like——
Mr. WEINER. Right.
Brigadier Gen. WORDEN [continuing]. Looking through a soda straw.
Mr. WEINER. Right.
Brigadier Gen. WORDEN. They take a long time to scan all the sky. And it is—today we don't scan the whole sky all the time. You——
Mr. WEINER. So you are taking little slices of the——
Brigadier Gen. WORDEN. Right So——
Mr. WEINER [continuing]. Pie and you are seeing things close and far in the same picture?
Brigadier Gen. WORDEN. Right.
Dr. BURNS. Exactly. And it is——
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Brigadier Gen. WORDEN. Now, to do the whole sky frequently requires new systems. Some of those systems we are going to build in the Defense Department to look at satellites. Other ones, the scientific community has proposed in this large synoptic survey telescope.
Mr. WEINER. All right. Listen. I am not the sharpest tool in the shed, but let me ask you this question.
Brigadier Gen. WORDEN. But that telescope, by the way, will survey the whole sky once a week that——
Mr. WEINER. I hear you. But let me ask you this question. I mean, maybe that new—maybe this isn't a technological problem. Maybe there is something about physics that I don't understand. Couldn't we develop a detection device, a telescope of something that does a quick zip around looking for just the big things, the big lights, the big—you can't do it?
Dr. MARSDEN. No. No. No.
Mr. WEINER. Physically—the laws of physics, I am just barking up the wrong tree.
Dr. MARSDEN. Well, we have done the big bright ones. You have got to find these when they are far away. You want to try to find them. The farther away, the better. And this requires a bigger telescope——
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Mr. WEINER. Okay. Now, let me just——
Dr. MARSDEN [continuing]. That shows——
Mr. WEINER. One final question. I appreciate, Mr. Chairman, you letting me pursue this. So we have a window of ignorance that lasts, what, a couple of hundred years like that we keep—we don't know the nearest stuff? So all of the statistics that we have gathered and all the information we found about ones that are bearing down on us, there really is a blind spot that we have going——
Dr. BURNS. I think it is—I think the——
Dr. MARSDEN. No. It is not a blind spot.
Dr. BURNS. Maybe the issue is these objects pass through the Earth's orbit every couple of years—a single object. It is not like we are watching——
Mr. WEINER. I see.
Dr. BURNS [continuing]. These things coming from far away. It is just that our orbits are crossing and occasionally, we get very close to one of the objects.
Mr. WEINER. I see. So the way I am visualizing it is like a bullet.
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Dr. BURNS. It is not like a—they are not attacking us in that sense. You know, they are not——
Mr. WEINER. Got you.
Dr. BURNS [continuing]. An Armada coming in at us.
Mr. WEINER. Got you. And just one final question. General, I have in my four years here in Congress never experienced a military man coming before a committee in uniform, active guy saying I am not speaking for my agency. I am just curious now, what is the relationship of this issue to the Air Force? It is a weird disclaimer. I have never seen a disclaimer like this when someone like you testifies. You don't speak for the Air Force. You are speaking for you but you are here as a Brigadier General. What is going on? Is this some Area 51 stuff going on or what? What is going on?
Brigadier Gen. WORDEN. That would be nice if it was. There is a long standing interest in this topic. I am an astronomer by background.
Mr. WEINER. Right.
Brigadier Gen. WORDEN. And I am probably one of the more senior scientists in uniform. So as such, I have been an active participant in these various studies. So from that perspective, I am recognized by my service and the Department as somebody that has, you know, opinions outside what might be official perspective. The second point is that we have agreed over the last few years that we will assist NASA in any way we can, you know, provided it doesn't cost much money. I mean, that is—because this is not an assigned mission. So our official position on this——
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Mr. WEINER. Because this isn't consistent with your mission of defending the country.
Brigadier Gen. WORDEN. Well, we have specific assigned missions of defending the country against, you know, hostile manmade threats. We also have an assigned mission that if task through—and there is a lot of laws about——
Mr. WEINER. Right.
Brigadier Gen. WORDEN [continuing]. You know, posse comitatus and so forth that we can assist civil agencies. We just established two days ago a command now responsible for the defense—Homeland Defense to assist that but we are not the lead agency. So it is kind of a delicate line, frankly, of testifying. So I was asked to do this by the Committee and so I am here as a scientist.
Mr. WEINER. But I would find nowhere in the Air Force budget a line item that I could look to see like research or things that are being developed to deal with this threat?
Brigadier Gen. WORDEN. That's correct. Thank you.
Mr. WEINER. Thank you, Mr. Chairman.
NEO Oceanic Impact Effects (Cont.)
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Mr. BARTLETT [presiding]. Thank you very much, and we will adjourn the hearing in a few minutes. And thank you all very much for your testimony. I would just like to, for a few moments, explore what is the most probable consequence of an asteroid hitting our planet, and it is going to hit in the water somewhere because we are what, three-fourths water? It is going to hit in the water somewhere. You don't have a chart with you probably that shows the relationship between the size of the asteroid and the height of the tsunami that would be produced by that if it hit in the ocean, but can you give us just in 30 seconds some idea as to the relationship of the height of the tsunami to the size of the asteroid and how far inland it would go?
Dr. MARSDEN. It depends whether it is in deep or shallow water as well.
Mr. BARTLETT. Well, let us assume it hits in the middle of the——
Dr. MARSDEN. Middle of the Pacific. Middle of the Pacific has got to be 200 meters before you get a respectable tidal wave that would do damage.
Dr. MORRISON. There are a variety of scientist who have looked at this and they don't fully agree with the numbers. But I am just trying to put together in my head—and I hope this is right—if you wanted a very rough number, take the diameter of the asteroid, divide it by 10 and you get the height of the wave that would propagate out to thousands of miles.
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Mr. BARTLETT. Okay.
Dr. MARSDEN. Yes.
Mr. BARTLETT. Okay. Now how much of a warning——
Dr. MORRISON. So a 100-meter asteroid would produce a 10-meter wave. A 500-foot asteroid would produce a 500-foot wave very, very approximately.
Mr. BARTLETT. Okay. How fast do those waves propagate and if one hit in the mid-Atlantic, you know, a 1000 foot—some of you before said that we could get a 1000-foot tsunami. That is——
Dr. MARSDEN. Hours. Hours.
Mr. BARTLETT. What?
Dr. MARSDEN. Hours.
Dr. MORRISON. Several hours.
Mr. BARTLETT. Several hours. Okay. How far would it go inland? Obviously Florida is a wash. Isn't it? Okay. If you live in Cincinnati, are you okay?
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Dr. BURNS. Cincinnati, you are fine.
Mr. BARTLETT. Cincinnati, you are okay. How about Pittsburgh?
Dr. MARSDEN. Yes.
Dr. BURNS. Yeah. Sure.
Mr. BARTLETT. You are okay in Pittsburgh. Philadelphia has got a problem.
Dr. MARSDEN. A bit.
Mr. BARTLETT. Okay. Scranton is on the border. I just wanted to get some feel for this because the most probable place that you are going to hit obviously is going to be water because we are three-fourths water, and I was concerned about how much. So we have several hours notice if one hits in the——
Dr. MARSDEN. In the middle. Yes.
Mr. BARTLETT. Yeah. I tried to get out of Washington on 9/11. It took me five hours to get out of Washington that day. So if there is a crisis like this, why, we are not going to depopulate our cities very quickly. Are we? Are we?
Dr. BURNS. Right.
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Mr. BARTLETT. Mr. Chairman, you have returned. Do you have any comments?
Chairman ROHRABACHER. Are you finished?
Mr. BARTLETT. I am finished, sir.
Chairman ROHRABACHER. All right.
Mr. BARTLETT. We were going to thank them and wrap it up.
Chairman ROHRABACHER. All right. So we have been taking care of big objects in space that could really cause millions of deaths, and we have been taking care of Saddam Hussein today. So good work, fellows, and you know, this is what people of our country expect us to handle, short term threats like that of Saddam Hussein. But also they expect us to take care of these long-term threats and to make sure that five years from now we don't have another near miss and that we have people sitting on a panel and saying, well, if one comes up within the next 18 months, we still couldn't handle it. Now, within five years I would hope that if we have this panel again or a similar panel within five years and who knows, Mr. Gordon may be the Chairman of this Subcommittee then. I might be sitting way down there. But I would hope when asked the question that the General or whoever is there states that, oh, yes, Mr. Congressman, we are prepared. If we spot one of these things heading for the Earth and we have 18 months to prepare for it, we know now that we can protect this planet. And I think that is vital and I hope the discussion that we have had today will motivate people in government and outside of government to take a look at this question and start doing what is necessary to take us some steps ahead because it is not—it is not irresponsible for us to look this far ahead to this potential threat even as we take care of threats that are closer to home right now. And I want to thank the witnesses.
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This has been a lively hearing especially for me as I am running out and back and forth like this. But I am sorry that I missed some of your testimony. But I know this has been very rewarding. Bart, do you have anything else you would like to add on this? There is something—there is one other point that I needed to make and it just isn't crossing my mind right now. But because of that I will advise Subcommittee Members that they may request additional information or they may place something into the record and ask unanimous consent that I be able to do so within one week of the date of this. And with that said, what was that——
Long-period Comets
Dr. MARSDEN. Long-period comets. We never addressed the long-period comets.
Chairman ROHRABACHER. All right. Why—I would like to ask you about that.
Dr. MARSDEN. Well, everything we have said has been about asteroids. We can do even the kilometer size. But, I mean, there are—there is the problem of the long-period comets. We are going to have that ultimately. They come from very great distances. And if we are lucky, we see them out at the distance of Jupiter and we maybe have two years. The Hale Bopp Comet a few years ago was discovered there and this was what, 40 kilometers across, something like that coming at us. This is a real problem that is—after we
have——
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Chairman ROHRABACHER. So comets——
Dr. MARSDEN. Comet—long-period comets are a problem we are always going to have.
Chairman ROHRABACHER. And we haven't even touched on that here.
Dr. MARSDEN. No, we haven't.
Chairman ROHRABACHER. Dr. Weiler, yes.
Dr. WEILER. Mr. Chairman, so you can sleep a little better tonight, the study that I talked about, which we are finally getting going and I am going to report back to you hopefully in June includes comments in terms of what we need to do for other—if we are going to build big telescopes on the ground or the space let us do it right one time——
Chairman ROHRABACHER. Okay.
Dr. WEILER [continuing]. And not keep building more telescopes.
Chairman ROHRABACHER. And let us not forget this too. The Chair admonished us to also think about these things as possible opportunities as well, not only because we can use them as transportation systems into the far out universe, and—or we can plant, you know—planting our equipment on there and things such as that. So——
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Dr. BURNS. And I think—if I might interrupt just for a second. In that regard, that is really one of the ways in which NASA should be involved is if we are going to do those sorts of things, we need to know where the objects are.
Chairman ROHRABACHER. Okay. With that said, thank you all very much again. This subcommittee is adjourned.
[Whereupon, at 12:25 p.m., the Subcommittee was adjourned.]
Appendix 1:
Answers to Post-Hearing Questions
ANSWERS TO POST-HEARING QUESTIONS
Responses by David Morrison, Senior Scientist, NASA Ames Research Center
Questions Submitted by Chairman Dana Rohrabacher
Q1. If the goal for surveying NEAs were extended to comprehensively include smaller objects of a few hundred meters in size, what new kinds of telescopes and technology would be needed?
A1. The technology is available to conduct a NEA survey to reach smaller and fainter objects than the current Spaceguard Survey, which emphasizes NEAs 1 km or larger in diameter. The primary requirement is for larger very-wide-field telescopes to reach fainter objects. The basic survey strategy for a larger telescope is the same; the only significant difference is that a telescope designed to detect fainter asteroids (astronomical magnitudes 23 to 24) would also make its own follow-up observations to ensure that an accurate orbit can be calculated for each new NEA.
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Q2. Do you believe a ''ground-based'' system for detecting NEOs is better than a space based system? Why?
A2. NEAs can be discovered by either ground-based or space-based telescopes or a combination of the two. Whether a ground-based or space-based survey is more cost-effectively is entirely dependent upon the size of the object being surveyed and the time allotted to complete the survey.
Q2a. Please estimate the differences in cost and technical difficulty between a possible future space-based vs. ground-based NEO survey that would include objects down to 300 m in size.
A2a. To achieve a complete survey of NEAs to a given size (such as 300 m diameter), the telescope (either ground-based or space-based) must be large enough to detect faint objects. The requirements for the telescope size are approximately the same whether it is in space or on the ground. The primary differences, therefore, are (1) the cost of launching and operating a telescope in space compared to a similar instrument on the ground, and (2) the ability to keep the telescope operational for the decade or more needed to complete a survey.
Q2b. What would be required for follow-up tracking and cataloging of the objects?
A2b. Any survey that focuses on NEAs much smaller than the 1 km objective of the current Spaceguard Survey will probably need to do its own follow-up observations as a part of the survey observing strategy. This is true whether the survey is ground-based or space-based. Additional follow-up for selected objects will be obtained with astronomical telescopes operating at optical and infrared wavelengths and with radar telescopes; most of these studies are likely to continue to be carried out primarily with ground-based telescopes.
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Q3. Based on surveys of experts, two panels of the NRC have recommended the joint development and operation, by NASA and the NSF, of a ''LSST'' for advanced surveys of NEOs as small as 300 m in size. Do you concur with this recommendation? Why or why not?
A3. Such studies are currently being carried out by science working groups within both NASA and NSF. NASA has accepted the mandate to catalog 90 percent of the NEOs with diameters of 1 km or greater; however, we expect that surveying the skies for NEOs as small as 300 m may be astronomically expensive. The NASA-sponsored SDT will attempt a preliminary answer to the questions of efficacy and cost.
Q4. How much time do you estimate we will have if the current or future NEO survey detects a large incoming asteroid or comet?
A4. The Spaceguard strategy, as first articulated in the 1992 NASA Spaceguard Working Group Report, is to gradually build up a catalogue, as complete as possible, of NEAs that have the possibility of colliding with the Earth in the future. Orbits are calculated for each of these discovered objects, and the conditions of any future close encounters are analyzed. If one of these NEAs is on an impact trajectory, it is generally possible to predict this collision decades to centuries in advance. This decades-to-centuries timescale for the prediction does not depend on the size of the asteroid. The orbits of smaller asteroids are equally stable to those of large ones, and their future positions can be predicted with equal precision. This survey strategy applies to any object that repeatedly comes into the inner solar system, either near-Earth asteroid or short-period comet. It does not apply to long-period comets. Our current ability to detect a new long-period comet and predict its orbit is in the range of 1–2 years. Fortunately, such long-period comets represent a very small part of the total impact risk. To date, we have not discovered a single asteroid that will impact Earth.
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Q4a. Will more complete surveys help increase warning time?
A4a. Not necessarily. Again, to date, we have not discovered a single asteroid that will impact Earth. For those not yet surveyed, we have no way of knowing.
Q4b. Will there be sufficient time to develop a mitigation strategy?
A4b. We do not know.
Q4c. Should agencies such as NASA or the DOD be working to develop a mitigation strategy ahead of time? What agencies do you recommend should participate?
A4c. NASA has the mandate to investigate the science of asteroids and comets. We are interested in determining their physical properties such as density, rotation rate, composition and origin. We take this mandate seriously. If an object should ever be discovered that might collide with the Earth, such scientific knowledge will be critical.
Questions Submitted by Representative Bart Gordon
Q1a. Regarding long-period comets, how much of a risk do they pose?
A1a. We know that the impact hazard is dominated by Near-Earth Asteroids (NEAs); estimates of the contribution from long-period comets usually put these at between one percent and five percent of the total hazard. Current research, while not definitive, also suggests that there are very few small comets (less than 1 km diameter), in which case the risk from small comet impacts may be negligible. Further study of the size distribution of comets would be useful to improve our understanding of the risk they may pose.
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Q2b. Is there anything that can be done to improve their detection rate, and if so, how difficult would it be and how much do you estimate it would cost?
A2b. If a deeper survey of NEAs is undertaken by extending the Spaceguard Goal to smaller sizes of asteroids, we will also improve our ability to detect long-period comets. NASA Headquarters has convened a Science Definition Team to provide information on which an estimated cost can be based.
Q2. What information do you believe is required to decide on a follow-up strategy for NEOs? What is the best way to gather that information, and how should the scientific community be involved in the process?
A2. The current Spaceguard Survey is highly successful. However, the operational strategy for any extension of the Spaceguard Goal to smaller sizes needs to be worked out in detail. These issues are currently being examined by science working groups within both NASA and NSF. Follow-up observations of selected objects by optical and infrared telescopes and by radar will also require continuing or enhanced access by asteroid astronomers to large telescopes and radar systems.
Question Submitted by Representative Anthony Weiner
Q1. Approximately 20 percent of the southern skies are not searched for NEOs because there are no active search efforts in that hemisphere. Yet, any NEO that now is undiscoverable in the south will be seen in the north—and the search will take considerably longer without a southern hemisphere research facility. Would you like to comment on that statement?
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A1. The present NASA NEO program is working to bring a southern hemisphere search effort on-line, however, we are currently using astrometric follow-up with observations from facilities in Australia and Argentina which actually removes some of the urgency for search operations from the southern hemisphere.
ANSWERS TO POST-HEARING QUESTIONS
Responses by Edward J. Weiler, NASA Associate Administrator for Space Science
Questions Submitted by Chairman Dana Rohrabacher
Q1. According to your testimony, NASA seems to be making good progress in meeting the Spaceguard goal of identifying 90 percent of Near-Earth Asteroids larger than one-kilometer in size by 2008. And yet you state that if the goal is extended to include smaller objects, NASA should not conduct the survey unless it is done from space.
Q1a. Please explain why you believe NASA should only be involved in the NEO survey if it includes a space-based survey?
Q1b. The recent National Academy of Sciences blue-ribbon panel, the committee on the Organization and Management of Research in Astronomy and Astrophysics (COMRAA), recommended that NASA continue to support ground-based telescopes that support NASA space missions. Does the ground-based NASA NEO survey support in-depth space missions to study asteroids and comets, like NEAR–Shoemaker and DAWN, by identifying nearby objects and providing information on the NEO population? Would a future survey of NEOs smaller than one kilometer in size benefit future NASA missions?
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Q1c. Do you believe that space-based telescopes are a better alternative than ground-based for future NEO surveys? Would space-based telescopes be more cost effective than ground-based telescopes? What space-based platforms, locations, and technology should be most highly considered for future NEO surveys?
A1a,b,c. As a space agency, NASA's assets and expertise are best suited to pursue space-based studies, including in situ explorations of these bodies—something only NASA can do. NASA is and will continue to be the lead agency relative to the scientific study and characterization of NEOs. NASA continues to fund scientists to use facilities run by those agencies responsible for ground-based telescopes. In fact, the Solar System Exploration Division within the Office of Space Science funds over $3M in individual grants to scientists for ground-based NEO research. What the Office of Space Science does not routinely fund is the operational cost of running ground-based telescopes.
NASA continues to support ground-based telescopes that deliver data required for our space-based science missions. In a few cases, ground-based NEO surveys have provided some useful information for NASA's in-depth missions to study asteroids and comets. We do not believe that there is much scientific interest in sending probes to the smaller asteroids; therefore, a survey of these objects would not likely prove useful in that regard. However, NASA has convened a team to investigate: 1) what will be required to complete a more inclusive survey; 2) what assets would be most appropriate should such and undertaking be considered; and, 3) what the realistic associated costs would be.
Q2a. You state in your testimony that it is premature to consider extending the current national survey program for surveys of Near-Earth Objects to search for smaller objects until there is a broad public discussion on what the search goals should be and what telescopes are needed. Yet the recent decadal review of solar system exploration conducted by the National Research Council included the aggregate recommendations of many scientists in all fields of solar system science. The resulting report (''New Frontiers in the Solar System: An Integrated Exploration Strategy'') recommends a ground-based survey of objects down to sizes of about 300 meters in size.
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Do you believe this study was adequate to determine future NEO survey goals?
A2a. The study was not adequate to determine future NEO survey goals. NASA requires a thorough, non-advocate review of the various implementation strategies and the realistic associated costs for each of them in order to optimize any such approach. While the National Academy of Sciences and other such groups suggest potential targets of investigation, it is up to the Administration/Agency to implement such suggestions, and up to the Congress to fund them.
Q2b. The report recommends that NASA and the National Science Foundation partner equally to build and operate a large ground-based survey telescope to regularly scan the sky for NEOs. Do you support this recommendation? Why or why not?
A2b. NASA does not support this recommendation, nor do the findings of the recently established National Astronomy and Astrophysics Advisory Committee (NAAAC), which was set up to advise NASA and NSF on collaborative efforts. The NAAAC recommended limited NASA contributions to a primarily NSF-led effort. The Committee recommended that NSF build such a ground-based telescope and NASA continue to do what it does best by assisting them in their effort by providing large detector arrays and data sets.
Q2c. The report recommends that NASA continue its strong support of ground-based observatories for solar system exploration, including planetary radar capability for follow-up observations of NEOs. Given NASA's cut and subsequent partial restoration of funds for NEO work at Arecibo last year, what are NASA's plans for continued support of ground-based planetary radar facilities?
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A2c. NASA funds approximately $4 million year of ground-based scientific investigations of NEOs, including the use of the Arecibo telescope. This exceeds the total amount of funding expended by NSF on planetary investigations each year. NASA did not substantially cut Arecibo funding last year, and we will continue funding scientists to use the Arecibo facility, but NSF is responsible for facility maintenance.
Q3. You state that a new Science Definition Team (SDT) has been appointed within NASA to consider technical issues related to extending the search for NEOs to smaller sizes. Will the SDT consider and compare both space-based and ground-based strategies? What is the scope and schedule of the SDT's activities? What has the SDT been directed to produce?
A3. The Science Definition Team will investigate: 1) what will be required to complete a more inclusive survey; 2) what assets would be most appropriate should such an undertaking be considered; and, 3) what the realistic associated costs would be.
Questions Submitted by Representative Bart Gordon
Q1. What are the costs and benefits of extending the Near-Earth Object survey to look for objects smaller than 1 km?
A1. To date, there has been no thorough, non-advocate review to decide what the benefits of such a search might be, nor is there a realistic assessment of the potentially significant costs involved.
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Q2. Beyond NASA's current activities to identify and catalog Near-Earth Objects with diameters of 1 km or greater, what do you see as NASA's future role in the search for Near-Earth Objects?
A2. NASA's unique assets and expertise are best suited to pursue any space-based studies of NEOs, including in situ explorations of these bodies—something only NASA can do. NASA is and will continue to be the lead agency relative to the scientific study and characterization of such objects.
Q3. In specific terms, how does NASA currently collaborate with other U.S. and non-U.S. Agencies and organizations to address the potential threat posed by Near-Earth Objects, and how would you propose that collaboration be conducted in the future?
A3. The National Aeronautics and Space Administration and Air Force Space Command established the Partnership Council in 1997. Membership has since been expanded to include National Reconnaissance Office, Unified Space Command, and the Defense Research and Engineering Command. The purpose of the Partnership Council is to find ways to save money, reduce risk, and integrate planning efforts in areas of mutual interest. In particular, the group is focused on collaborative efforts and joint opportunities that allow the most effective and efficient implementation of the Nation's space program. The Partnership Council is composed of the leadership of each member organization.
Q4. Dr. Weiler, in your testimony you stated that with respect to expanding the search for potentially hazardous Near-Earth Objects: ''Before any further effort is undertaken, we would want input from the scientific community as to how this subject should be approached. . .'' However, the National Research Council's Solar System Exploration Survey, which was commissioned by you, has now recommended that (in order to address the Survey's Key Question #10: ''What hazards do solar system objects present to Earth's biosphere''): ''. . .NASA partner equally with the National Science Foundation to build and operate a survey facility, such as the Large-Aperture Synoptic Survey Telescope (LSST).''
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Q4a. That seems like a pretty clear recommendation by the scientific community. Is NASA prepared to accept the NRC's recommendation? If not, why not?
Q4b. What, if any, additional scientific input do you think is required, and what is your specific plan and timetable for receiving that input?
A4a&b. NASA does not support this recommendation, nor do the findings of the recently established National Astronomy and Astrophysics Advisory Committee (NAAAC), which was set up to advise NASA and NSF on collaborative efforts. The NAAAC recommendation limited NASA contributions to a primarily NSF-led effort. The Committee recommended that NSF build such a ground-based telescope and NASA continue to do what it does best, which is to assist them in their effort by providing large detector arrays and data sets. While the National Academy of Sciences and other such groups suggest potential targets of investigation, it is up to the Administration/Agency to implement such suggestions, and up to the Congress to fund them.
NASA's primary goal with regard to NEOs is to complete the Spaceguard Report goal of cataloging 90 percent of those objects larger than 1km by 2008, since they pose the biggest threat to our planet. It is as important, if not more important, that we continue to pursue missions, which will help us understand and categorize the properties of these objects. Our exploration efforts to date—and those on the horizon in our current budget run-out—total $1.6 billion. These missions were peer-reviewed and competitively selected, and they include NEAR–Shoemaker (which, after sending back important data on asteroids 253 Mathilde and Eros, actually landed on the surface of Eros), Deep Impact, Stardust, Deep Space I, and Dawn.
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To help determine what NASA's future role regarding NEOs should be, NASA has convened a Science Definition Team to investigate: 1) what will be required to complete a more inclusive survey of NEOs; 2) what assets would be most appropriate should such and undertaking be considered; and 3) what the realistic associated costs would be. The team's report is due in June 2003.
Questions Submitted by Representative Anthony Weiner
Q1. How much money has NASA invested in the construction, development, instrumenting, and operation of ground-based telescopes in the last 10 years, including the funds spent on the Keck Observatory, the interferometer any at the Keck telescopes, and the upgrade of the Arecibo radio antenna and radar system?
A1. NASA does support some critical ground-based observations when they are required for the success of its space-based missions. However, this only occurs in the rare instances where other agencies do not provide adequate ground-based operational support. Over the past 10 years, NASA has spent approximately $160 million for ground-based astronomy (e.g., Keck, Infrared Telescope Facility, Arecibo).
Q2. Given that quantity of funds committed by NASA to ground-based observing, please explain why you now say it is inappropriate for NASA to fund more ground-based telescope(s) to search for NEOs?
A2. NASA is not the lead agency within the government for the support of ground-based astronomy; that role is played by the NSF's Division of Astronomical Sciences. Their charter (http://www.nsf.gov/mps/divisions/ast/about/c–overview.htm) clearly states:
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The NSF is the lead Federal agency for the support of ground-based astronomy. Funding is provided through grants, contracts, and cooperative agreements awarded in response to unsolicited, investigator-initiated proposals.
Program areas in the Division of Astronomical Sciences (AST), supported primarily through individual investigator awards, include planetary astronomy, stellar astronomy and astrophysics, galactic astronomy, extragalactic astronomy and cosmology. A broad base of observational, theoretical, and laboratory research is aimed at understanding the states of matter and physical processes in the Solar System, our Milky Way galaxy, and the Universe. Funding is also available for advanced technologies and instrumentation, university radio facilities, and a variety of special programs.
NSF's AST supports the development and operation of four National Astronomy Centers the National Optical Astronomy Observatory (NOAO), the National Solar Observatory (NSO), the National Radio Astronomy Observatory (NRAO), and the National Astronomy and Ionosphere Center (NAIC).
Q3. Given that the ground-based NEO surveys funded by NASA are in direct support of NASA's spacecraft missions and that NASA has, historically, conducted ground-based research in support of spacecraft missions, please give an example of a large-scale ground based telescopic survey funded by NSF that was made in direct support of a spacecraft mission. If there has not been one, please explain why NSF should be expected to start doing so now by funding NEO surveys.
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A3. The ground-based NEO surveys funded by NASA are being conducted to comply with a Congressional directive of identifying 90 percent of all NEO's 1 km or larger within 10 years; these NEO surveys are not conducted in support of NASA spacecraft missions. There has never been an NSF-funded ground-based survey in direct support of a NASA space-based mission.
Q4. In response to your reference to the NEO Science Definition Team that is currently being funded by NASA, and the NSF study with a similar charter that is currently being conducted as a part of the Large-Aperture Synoptic Space Telescope (LSST) study at National Optical Astronomy Observatories (NOAO), and in recognition that there has been an overlap in the membership of these two panels, please explain the apparent duplication of effort between the parallel studies of the NEO hazard being conducted simultaneously by NASA and NSF.
A4. The teams actually have two different objectives. The role of the NASA SDT is to provide an objective, non-advocate assessment of whether any additional search is needed, and if so, what resources would be required to expand the search for NEOs to smaller objects. This assessment would help determine what role, if any, NASA would play in this effort.
The role of the LSST group is to design a multi-purpose facility that would search for NEOs greater than 300 m; advocacy is one of its goals. In addition, there already exists an Air Force-funded program called PANSTARRS to survey the skies for smaller objects.
Q5. Is it possible for NASA to fund NEO searches out of its existing budget, and if so, can you estimate the total cost of funding needed for detection of ALL NEOs one kilometer in diameter or greater? Can you also estimate the additional cost of detection of ALL NEOs less than one kilometer?
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A5. NASA has adequate funding identified to complete its commitment to Congress of identifying 90 percent of all NEO's 1 km or larger within 10 years; the total cost in real year dollars for this effort is approximately $40 million. At this point we cannot estimate the additional cost of detecting smaller-class objects. Identifying each and every NEO smaller than 1 km is virtually impossible.
Q6. Is there a protocol in place in the event that an Earth-threatening object is detected? To what organizations/offices would the problem be reported? What mitigation steps would be taken?
A6. Observers in this country and from other nations report discoveries of NEOs to the Minor Planet Center (MPC) of the International Astronomical Union (IAU). The MPC is located at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. The MPC is an open repository. The data needed to determine if any asteroid will present a hazard to the Earth in the future are thus available to anyone with the capability to project the motion of both the NEO and the Earth into the future from the orbital elements. There are a number of groups both in this country and in the rest of the world who can do such calculations. The IAU has established a Working Group on Near-Earth Objects (WGNEO), and this group has established a voluntary technical review process. In this process, investigators who calculate that a newly discovered NEO present a hazard to the Earth, are asked to inform the Chairman of the WGNEO who will ask a hazard review team to review the prediction. If the hazard review team agrees, the information is placed on the IAU web site. This peer review process was developed after several ''false alarms'' were reported over the last few years and has worked very well. With the Internet, the review process is extremely rapid. The website for the WGNEO is http://web.mit.edu/rpb/wgneo/.
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ANSWERS TO POST-HEARING QUESTIONS
Responses by Joseph A. Burns, Irving Porter Church Professor of Engineering and Astronomy, Cornell University
Questions Submitted by Chairman Dana Rohrabacher
Q1. The recent recommendation from the Solar System Exploration Survey report of the National Research Council recommends that NASA and the National Science Foundation cooperate to build and operate a large ground-based survey telescope to extend the national survey of Near-Earth Objects (NEOs) to comprehensively include smaller objects down to 300 meters in size.
Q1a. Why is 300 meters a good target size?
A1a. As various witnesses stated, today's goal of finding 90 percent of 1 km objects is designed to identify the ''global killers,'' those asteroids that could devastate our planet. Impacts by smaller objects have more modest effects but occur more frequently; for example, 300 m asteroids are ten times more abundant than 1 km objects. Crashes of 300 m asteroids into oceans will ''merely'' cause regional catastrophes (such as the destruction of New England or the California coast) via the tsunamis that would be generated; 300 m impacts could also destroy an area the size of Virginia if they instead hit on land.(see footnote 5) Even objects with diameters below 300 m could, if ''aimed'' precisely, level large urban centers such as metropolitan New York or Tokyo; however, because such localized targets cover only a small fraction of Earth's surface, the overall risk of these latter impacts is low.
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That is, different risks are associated with different impactor sizes. The 300 m limit that we have discussed is set more by today's technological capability rather than by some intrinsic change in the nature of the threat posed at this size. Thus the size limit of 300 m is a matter of practicality, not a fundamental size that must be attained. To detect such a size would require a telescope of about 6 m diameter; this would give a significant improvement in capability, but telescopes of such size are commonly built today and are affordable. No formal cost vs. risk analysis, beyond the above, has been carried out to my knowledge.
Q1b. How much would such a telescope cost to develop? What about the costs of ongoing survey activities and data management?
A1b. According to the 2001 Astronomy & Astrophysics Decadal Survey,(see footnote 6) the LSST is projected to cost $140 million (in FY 2000 dollars); this includes $83 million for capital construction and $42M for data processing and distribution for 5 years of operation; routine operating costs, supporting a technical staff of about twenty, are estimated at $3 million per year. It should be kept in mind, however, that these are preliminary figures, and that this particular LSST design is only one of several study concepts. By way of comparison, NASA's current entire program for investigating Near-Earth Object has an annual budget of $3.5–$4.0 million; these funds support NEO discoveries and follow-up observations, physical characterization, and orbit studies leading to impact predictions.
Q2. In his testimony, Dr. Weiler stated that NASA should not be involved in future extended surveys for NEOs if they use ground-based telescopes. And yet the recommendation from the National Research Council report explicitly states that NASA should partner with the National Science Foundation to build and operate a ground-based survey telescope to search for NEOs.
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Q2a. Why should NASA be involved at all in a ground-based survey effort?
A2a. First, I should say that I feel that Dr. Weiler's position that NASA should not be involved in ground-based facilities is apparently at odds with the NASA Act of 1958, which authorizes NASA to ''acquire, construct, . . .operate and maintain laboratories, research and testing sites and facilities.'' More recently, the final recommendation of the Augustine report (''U.S. Astronomy and Astrophysics: Managing an Integrated Program'', 2001) is that ''NASA should. . .support critical ground-based facilities and scientifically enabling precursor and follow-up observations that are essential to the success of space missions.'' (p.44)
An extensive ground-based survey of the near-Earth environment is consistent with various NASA objectives:
1) From the point of view of space-mission planning, a survey like that designed by the LSST community would be useful to identify the best and most accessible targets for flights to asteroids, comets and Kuiper Belt Objects. At present, this population of targets is not well understood as indicated by recent spacecraft measurements. The information from follow-up studies to that survey would also enable NASA to choose the most meaningful instrument packages for such missions.
2) From a technological standpoint, developing the equipment and software necessary to conduct a ground-based survey should benefit future NASA space missions.
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3) Apart from these practical reasons, good scientific motives exist to understand the nature of the Near-Earth population. These objects bombard the Earth; they carry primitive organic materials; and in the long run they may provide relatively cheap resources for space-travelers.
Furthermore, some in the planetary community believe that the NSF has abdicated its responsibility for supporting planetary research (its current budget in this discipline is much less than one percent of NASA's). NASA's involvement would ensure that the LSST would be used to study both solar system bodies as well as much more distant targets. In addition, scientific monitoring activities, such as meteorological measurements, have traditionally been carried out by governmental agencies other than NSF, which instead primarily funds small, short-lived individual research grants.
Q2b. Does ground-based NEO monitoring, such as with planetary radar facilities at Arecibo, need NASA support? Why or why not?
A2b. In order to develop appropriate mitigation strategies for averting asteroid collisions, it is crucial that the physical properties (density, homogeneity, strength, surface character, etc.) of near-Earth asteroids be measured. This will require employing a suite of ground-based instruments (infrared telescopes, radar facilities, etc.) and ultimately space missions. Radar detections can also be used to dramatically improve orbital positions, thereby pinpointing orbital crossing times. The scientific and aerospace engineering communities have no strong preference (that I am aware of) that these investigations be carried out by any particular agency (e.g., NASA rather than the NSF), although historically the former has been carrying the vast bulk of the load.
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Q2c. What unique contributions can NASA and the National Science Foundation make toward the effort?
A2c. The NSF can contribute its experience in constructing and operating ground-based observatories, such as NOAO (National Optical Astronomical Observatories) or NRAO (National Radio Astronomy Observatory). NASA can provide its knowhow in successfully managing large scientific projects. It can furnish its broad background in the scientific study of solar system bodies, especially in the handling of large scientific data sets. NASA's expertise with sensitive detectors is also likely to be valuable. The Solar System Exploration Survey felt that NASA's involvement would ensure that two of the leading science objectives for the LSST (observations and characterization of NEOs and Kuiper Belt Objects), as identified by the Astronomy and Astrophysics Decadal Report (pp. 38–39), would be completed.(see footnote 7) Finally, NASA is uniquely qualified to coordinate the ground-based research with spacecraft studies and thereby to guarantee that the target properties—so critical for effective mitigation—are properly measured.
Questions Submitted by Representative Bart Gordon
Q1. In your testimony, you state that the National Research Council's Solar System Exploration Survey ''. . .identifies the exploration of the terrestrial space environment with regards to potential hazards as a new goal for the Nation's solar system exploration enterprise.''
Q1a. Why did the members of the Survey believe that Near-Earth Object hazards research should become an explicit goal for solar system exploration?
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A1a. There is a growing recognition within the scientific community that we need to be more responsive to the public at large. The inclusion of NEO hazard research as an explicit goal for solar system exploration is based on the understanding that the future of our planet Earth is a question of considerable concern to the general public. In addition the solar system exploration community is in a unique position to address this valid concern.
In addition, the study of NEO hazards fits into recent attempts to address a broad range of topics:
1) Since the space age began nearly a half-century ago, impacts have been demonstrated to play a vital role in the evolution of the solar system and its constituent bodies (e.g., the current paradigm that the Moon was born following a massive collision with Earth). Although most impacts occurred in the first billion years of the solar system's history, events such as the impact of Comet Shoemaker-Levy 9 on Jupiter in 1994 show us that powerful cosmic collisions are still happening today. It is important to understand the effects of ancient and ongoing collisions.
2) Previous research on NEOs indicates that a population of massive projectiles are on Earth-crossing orbits. We need to know the sources and properties of these objects.
3) Even though not mentioned directly in our report, national security satellites have determined that small objects bombard Earth's upper atmosphere frequently. As General Worden testified during the hearing, these smaller objects do not penetrate the atmosphere but—by possibly misleading surveillance satellites to conclude that a nuclear attack is taking place—they may trigger an unwarranted response.
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Q1b. In practical terms, what should be done to achieve the goal?
A1b. To assess the NEO threat accurately, research must be carried out on several fronts. Astronomers need facilities such as the LSST to identify the vast majority of the population. Follow-up studies with infrared telescopes and radar are crucial to characterize the physical properties of the members. Spacecraft observations will ultimately be required to assure that the correct inferences are being made from ground-based measurements and to ascertain in detail the characteristics of asteroids at depth. Throughout these investigations, associated theoretical work is needed to place the results in context.
Questions Submitted by Representative Anthony Weiner
Q1. What fraction of the observing time with LSST (Large-aperture Synoptic Survey Telescope) would be dedicated to the correct observing cadence for detecting and following up NEOs?
A1. This issue is under current review by the instrument study team. Three questions are being addressed, one being the precise strategy (different filters, exposure times, revisit frequencies, etc.) to be used; another concerning the efficacy of optimized, less than all-sky coverage; and the final one being how effective any particular strategy of cadence and coverage would be in meeting other scientific goals. A recent workshop proposed that an optimized search strategy could be devised that would be quite successful in discovering the most hazardous NEOs with less than all-sky coverage. However, consensus has not yet been reached. One knowledgeable observer states that obtaining 90 percent completeness down to around 300 m diameter in ten years is achievable using of order half of the observing time, but more work is needed to confirm this opinion.
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Q2. Please clarify the need for LSST for NEO surveying when Pan-STARRS has already been funded by the Air Force.
A2. The Pan-STARRS project is useful in doing technology development (data handling is particular critical) for the LSST effort; in fact the Pan-STARRS documentation describes itself as a precursor to a larger follow-on instrument, such as the LSST. Through-put (the product of collecting area times sky coverage) is the vital measure in how well a telescope can detect faint, fast-moving objects, such as the 300 m to 1 km sized asteroids that are the goal of the LSST NEO survey. In that regard, keep in mind that the combined collecting area of the four Pan-STARRS telescopes is less than half that of the proposed LSST collecting area.
ANSWERS TO POST-HEARING QUESTIONS
Responses by Brian G. Marsden, Director, Minor Planet Center, Smithsonian Astrophysical Observatory
Questions Submitted by Chairman Dana Rohrabacher
Q1. If the current survey goal for Near-Earth Objects (NEOs) is extended to comprehensively include smaller objects of a few hundred meters in size, how would the Minor Planet Center need to be augmented to support the increase in data?
A1. If the current NEO survey goal is extended to include objects down to a few hundred meters in size in a comprehensive manner, I estimate that the current Minor Planet Center staff of just three people would need to be extended to 10–12 people. For one thing, it would be necessary to have a round-the-clock operation, since observations are being made at and reports are being received from different longitudes all around the world. Although it is the efficient operation of computers and communications that is key to the work of the MPC, computers do have to be fed and results examined, and it is probably desirable to have two people available at all times. Furthermore, some of the staff (perhaps three or four) need to be experienced computer programmers, and there is also a need for two (I would say) systems engineers to keep the computers functioning. With benefits, one person would cost roughly $100,000 per year—rather more in the case of the systems engineers. The eight or so computers the MPC currently uses would perhaps require doubling, but nowadays computers are cheap in comparison with people.
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Q2. Once discovered, how often does a NEO need to be ''re-observed'' in order to keep its orbital parameters accurate? How much do amateur astronomers contribute to this follow-up tracking effort currently?
A2. A typical NEO candidate, recognized as a possibility from observations in the U.S. (say) within a matter of hours, is usually fully demonstrated as an NEO from observations from Europe perhaps 12 hours after that and from the U.S. the next night, so that the formal announcement with a tolerably established orbit can be made within 36 hours of the initial observations. After that, observations are usually needed less frequently (unless the object is very near the Earth), with data sets just a couple of nights a month being sufficient as long as the object is reasonably placed for observation (in a dark sky and not too faint). Amateurs actually help with these observations to a significant extent. It is also very important to try and ''recover'' the NEO when observations again become possible after a long period (perhaps years) of unobservability (with the object too faint and/or behind the sun). Amateurs are usually of less help with this because the object will often be too faint for them. Amateurs can, however, be very helpful at recognizing the new NEOs on old professional photographs from past years. Past observations can be just as good as future observations for securing accurate orbital parameters. After an orbit has been determined from observations some years apart, only occasional further monitoring is necessary.
Q3. If the survey is extended to comprehensively include smaller objects, could amateur astronomers still keep up with the tracking effort?
A3. Since the extension to smaller objects is going to mean the detection of fainter objects and require the use of larger telescopes, such as the proposed Large Synoptic Survey Telescope, it will be very difficult for amateurs to contribute to the follow-up efforts in the future. Even their use of archival images will also be jeopardized, because the smaller objects are less likely ever to have been accidentally recorded on old photographs. This is all going to mean that there will be greater pressure on the new discovery telescopes also to do their own follow-up, not necessarily deliberately, but as a semi-accidental consequence of their continuing search efforts.
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Q4. What is the role of the international community for surveys of NEOs?
A4. The present international NEO effort mainly involves follow-up, with very little discovery activity. Most of the observations are made in Europe, with countries like the Czech and Slovak Republics taking the lead, followed by Italy, Spain and Sweden; there is some amateur activity also in Austria, Germany, France, Portugal and the U.K. Outside Europe, there is some professional and amateur activity in Japan, Australia, New Zealand and Uruguay, and amateur activity in Brazil and Canada, but that's about it. The only country seemingly committed to increasing its professional activity in the future (to include searches) is Japan.
Q5. If military surveillance telescopes are used in future surveys for NEOs, do you foresee any problems with quickly releasing the data to the international community? Do you have any suggestions on how to handle potential problems of data sharing?
A5. At the present time, the two most effective NEO surveys, LINEAR and NEAT, do utilize military surveillance (satellite-tracking) telescopes. These surveys filter out the observations of satellites and submit the remaining observations (99 percent of them of main-belt asteroids, one percent of NEOs and of comets generally) to the Minor Planet Center within a matter of hours. The programs are very cooperative, and the process works well. The Minor Planet Center, in turn, is permitted to release to the international community the observations of objects (asteroids, comets and NEOs generally) that are identified or linked. Any remaining unidentified, unlinked, single-night detections are returned to the programs after one month. Most of these are spurious. observations, not of real objects. I would hope that similar arrangements could be made for any other military surveillance telescopes that would be used in future surveys.
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Ouestions Submitted by Representative Bart Gordon
Q1. There are objects called ''long-period comets'' that are not routinely picked up by current observational surveys of Near-Earth Objects. However, it is my understanding that such comets could represent a significant hazard due to their high impact energies.
A1. The problem with the long-period comets is, not so much that they aren't being found by the current NEO survey programs, but that, by their nature, they are found too late for there to be effective mitigation, if one were to be found on a collision course. The whole point about the asteroid surveys is that the asteroids travel around the sun in a matter of just a few years, going out generally no farther than Jupiter before they come back. The same is true of the short-period comets. If we find that one of these objects is going to hit the Earth, the chances are that we shall know about this long in advance, with the object going around the sun many times before the impact, with the impact at least decades, if not centuries or more, in the future. Not only does this give us time to complete our inventory, but it also gives us time to study our enemy carefully and develop specific mitigation strategies long before it is necessary to apply them—unless we are terribly unlucky and find the object on the approach that will actually impact us. Long-period comets, on the other hand, take at least two centuries (by definition), and generally a lot longer, to orbit the sun, and they come in from great distances, way beyond Jupiter, where we have no possibility of detecting them in our present surveys. If the Earth is to be hit by a long-period comet during the foreseeable future, this will therefore inevitably be on the same pass that we actually discover it—if, indeed, we do discover it before it hits. The point is that we shall certainly not have the luxury of discovering the comet decades ahead. The best we are likely to do is about two years, and that (and it will more likely be a lot less) is considered too short for effective mitigation.
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Q1a. How much of a risk are long-period comets?
A1a. Although some have estimated the risk of long-period comets as high as 25 percent of the risk of the asteroids, I think this figure is far too high. (It may partly depend on comparison of the impact energies, which are indeed much greater for the long-period comets than for the asteroids.) I estimated more like two percent already several years ago, and I understand that others are now also giving figures like this. Of course, after we have discovered all (or essentially all) of the asteroids (down to a size where impact would do no damage), essentially all of the danger would be from the long-period comets. The problem never goes away.
Q1b. Is there anything that can be done to improve their detection rate, and if so, how difficult would it be and how much do you estimate it would cost?
A1b. If we improve on the present surveys for asteroids by using larger telescopes to go down to fainter and smaller objects, there will necessarily also be some improvement with regard to the long-period comets in that it should be possible to find them when they are farther away, so we could gain some time before potential impacts—like four years instead of two years. The more comprehensive surveys necessary to find long-period cornets routinely a decade or more ahead of potential impact will require observations from space (perhaps even from probes sent to the outer solar system) and be so extremely expensive it is probably completely impractical to think of them at this time, while the danger is still small in comparison with the danger from asteroids.
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Q2. Should we wait until the current survey of NEOs is completed before we decide what, if any, follow-on survey should be undertaken? If not, when should we start the follow-on survey, and why?
A2. I think we should already have been deciding on the follow-on survey a couple of years ago, so that we could now already be starting to implement it. The fact that we have already found more than 620 kilometer-sized objects (three-quarters of them with very good orbit determinations) is great, but it really does not matter whether there are 1000, 1200 or even 1500 altogether and whether we find ''90 percent'' by the end of 2008. We'll find them within at most a few years after 2008. The important thing is that we now have so much experience with the search and that we are already finding a fair number of smaller objects, with more than 1700 altogether down to 200 meters or so (almost half of them with good orbit determinations) and the number currently increasing at a rate of 400 per year. Nevertheless, we have so far found only perhaps three percent of the 200-meter objects, and at this past year's rate it will take a century to come even close to completing the job. We should therefore embark seriously on the extension to smaller objects as a goal as soon as possible.
Questions Submitted by Representative Anthony Weiner
Q1. Please elaborate on the threat of impacts by long-period comets and its significance compared to that from asteroids.
A1. The whole point about the asteroid surveys is that the asteroids travel around the sun in a matter of just a few years, going out generally no farther than Jupiter before they come back. The same is true of the short-period comets. If we find that one of these objects is going to hit the Earth, the chances are that we shall know about this long in advance, with the object going around the sun many times before the impact, with the impact at least decades, if not centuries or more, in the future. Not only does this give us time to complete our inventory, but it also gives us time to study our enemy carefully and develop specific mitigation strategies long before it is necessary to apply them—unless we are terribly unlucky and find the object on the approach that will actually impact us. Long-period comets, on the other hand, take at least two centuries (by definition), and generally a lot longer, to orbit the sun, and they come in from great distances, way beyond Jupiter, where we have no possibility of detecting them in our present surveys. If the Earth is to be hit by a long-period comet during the foreseeable future, this will therefore inevitably be on the same pass that we actually discover it—if, indeed, we do discover it before it hits. The point is that we shall certainly not have the luxury of discovering the comet decades ahead. The best we are likely to do is about two years, and that (and it will more likely be a lot less) is considered too short for effective mitigation. The good news is that, object for object, the danger of impacts from long-period comets is only perhaps two percent of that from asteroids. Of course, after we have discovered all (or essentially all) of the asteroids (down to a size where impact would do no damage), essentially all of the danger would be from the long-period comets. The problem never goes away.
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Q2. Given the Minor Planet Center currently has only three staff and limited funds, what do you think should be done to support its development/sustained operations?
A1. To carry out its current mission reasonably, I think the Minor Planet Center needs to be manned for 16 hours a day, seven days a week. That requires a minimum of five people (rather than the current three), including a qualified systems engineer to manage the Center's computers. If there is to be an extension to smaller objects, along the lines of using the proposed Large Synoptic Survey Telescope, round-the-clock operation will be needed, probably with two persons present at any time, and therefore requiring 10–12 people. Since the Minor Planet Center is international in scope, I think the source of funds should also be international. The Organization for Economic Cooperation and Development, with 30 member states (including the U.S. and every member state of the European Union), has an obvious and stated interest in the subject and may be good avenue for procuring international funding in an appropriate manner.
ANSWERS TO POST-HEARING QUESTIONS
Responses by Brigadier General Simon ''Pete'' Worden, U.S. Air Force
Q1a. What are the advantages of using space-based detection systems over ground-based, and vice-versa? Please explain.
A1a. Space-based systems have two advantages. First, they can observe 24 hours a day and are not blocked by weather. This means that for fast-moving objects—the ones that are coming closest to the Earth, they have the best chance of both finding them and getting a good track to predict whether or not the object might impact. Second, space-based systems are able to search much closer to the sun. Many of the most threatening objects, particularly comets approach Earth from this direction. Thus, space-based systems have the best chance of detecting such objects.
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Ground-based systems have traditionally been much cheaper to build and operate than space-based systems. However, the recent development of low-cost microsatellites is changing this situation. Nonetheless, to see very small objects or to follow potentially threatening objects when they are far from the Earth—a necessary function if we are to get truly accurate orbits and predictions of whether an object will impact—requires large optical systems several meters or more in diameter. Such systems are not possible to mount on small, microsatellite space systems. Thus, for the foreseeable future the most effective NEO search network will require both space- and ground-based detection systems.
Q1b. How do these proposed military surveillance systems compare with the Large-Aperture Synoptic Survey Telescope (LSST) proposed for future NEO surveys by scientists surveyed by the National Research Council? Do we need both?
A1b. Both future military space surveillance systems and the LSST are designed to address a range of problems. Both systems would include missions other than NEO identification and tracking. Military systems must survey Earth-orbiting satellites and the LSST includes astrophysical objectives separate from NEOs. Neither the military system nor the LSST can address the full range of missions of the other. In particular the LSST will perform very deep surveys of NEOs—providing key data for establishing precise orbits for NEOs. However, the LSST will cover the entire sky relatively infrequently. Conversely, military surveillance systems must cover much of the sky every few hours, but will not observe nearly as faint objects. If a potentially threatening object is approaching rapidly the military systems will have the best chance of picking it up. The LSST will provide the necessary data for establishing information on threats that might not materialize for centuries or more. In my opinion both systems are needed and could, together provide us with an effective NEO suite.
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Q2. If the military proceeds with ground-based or space-based surveillance systems for NEOs, would this replace the need for NASA or other agency involvement? If not, how can NASA and other agencies best cooperate with the military in NEO survey and response activities?
A2. If the U.S. military were to be assigned the mission of surveillance of NEOs in addition to other surveillance missions it currently has that would not change the requirement for other U.S. Government agency involvement in addressing the NEO problem. A wide variety of ground- and space-based scientific investigations outside the conventional purview of the U.S. military are essential toward gaining enough information about the NEO threat to properly assess it and devise responses if necessary. In my opinion the U.S. Government will need the combined efforts of both its security agencies and its scientific agencies such as NASA and NSF to meet the requirements. I believe a clear delineation of responsibilities and roles could be very helpful within the U.S. Government. I also believe that NASA and the DOD are beginning to study what's needed as part of the ongoing, high-level Space Partnership Council established several years ago.
Q3. You state that the biggest problem regarding mitigation of an asteroid threat is the absence of ''command and control'' structure for such an operation. Do you believe plans for mitigation of a threatening NEO should be made before such a discovery is made? What agencies do you feel should be involved in such preparations, and which agency should take the lead?
A3. Centuries of military operations have shown that almost all successful operations—particularly those which meet a surprise threat are based on clearly articulated and understood command and control structures. Not only must these be in place well before the crisis arises, but they must also be practiced and exercised. Meeting any threat, including NEOs requires a similar pre-positioned structure and procedures. While the U.S. military is probably best versed in planning for and executing operations such as will be needed to meet an NEO problem, the decision as to who should be involved, who is to be in charge, and perhaps most important who will budget for the effort is one which I leave to national leadership. I would advise that the U.S. military is an important participant and I'm confident that it would do an outstanding job if asked to lead such an effort.
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Q4. What issues such as restrictions on data release to the general public and international scientific community would need to be addressed if the U.S. Air Force were to conduct NEO surveys or serve as a clearinghouse for such data?
A4. The U.S. military provides much data openly worldwide. Perhaps the best example is the GPS satellite system. However, with any military system serving both military and non-military needs care must be taken to ensure that released data does not compromise the military capabilities that the system must also meet. I am confident, however, that future military surveillance systems can be so configured that all-relevant data on NEOs and their impact threat may be fully released internationally without compromising other military functions of such systems.
Appendix 2:
Additional Material for the Record
81931i.eps
STATEMENT SUBMITTED BY WILLIAM S. SMITH, JR.
PRESIDENT, ASSOCIATION OF UNIVERSITIES FOR RESEARCH IN ASTRONOMY, INC.
THE HAZARD PRESENTED BY SMALL ASTEROIDS AND STRATEGIES FOR DETECTING THEM
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Programs are currently in place to discover potentially hazardous Earth-crossing asteroids (PHAs) larger than one kilometer in diameter. The census should reach its goal of being approximately 90 percent complete by 2008.
Two surveys of scientific priorities for the next decade conducted by the National Research Council (Astronomy and Astrophysics in the New Millennium and New Frontiers in the Solar System) have recommended that discovery be extended to asteroids of smaller size.
The following statement summarizes the reasons for this extended survey and a potential strategy for carrying it out.
HAZARD PRESENTED BY ASTEROIDS LESS THAN ONE KILOMETER IN DIAMETER
Asteroids with sizes smaller than one kilometer in diameter present a significant hazard. While larger asteroids cause more damage per event, they also occur much less frequently. Somewhere in a size range above 1 km (0.6 miles), impacts cause global environmental effects that can put the entire population of the Earth at risk, even those that are a hemisphere away from the impact site. Such events may occur only once in a million years. In contrast, a ''Tunguska-sized'' impact, like the one that occurred over Siberia in 1908, occurs perhaps once per 1,000 years. The quantitative assessment of the hazard presented by smaller asteroids is currently in progress. The actual damage that will occur depends on a number of factors, including not only the size of the asteroid and the frequency of occurrence but also on modeling of such effects as the blast damage, earthquakes, fire, and tsunamis. The extent of the damage also depends on the composition of the asteroid and the angle at which it impacts the atmosphere.
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The large damage that would be caused by the impact of an asteroid larger than 1 km in diameter is the concern of the present ''Spaceguard Survey.'' With the technology at hand a decade ago, when Congress first called for a study of the impact hazard, the cost to conduct a survey of these most hazardous large NEOs were found to be worth the projected savings in terms of the risk posed by such large impacts. That task is now well underway, and much improved technology has become available. Accordingly, it is appropriate to ask whether it is worth implementing a next generation survey to find smaller and less hazardous, but more frequent impactors.
The smallest asteroid that can penetrate the atmosphere to or near enough to the ground to cause damage is about 50 meters (150 ft) in diameter. Smaller objects generally explode high in the atmosphere, at most dropping a few small fragments (meteorites) to the ground nearly without harm. There is no recommendation from studies by the National Research Council at the present time to search for asteroids smaller than 200–300 meters because of the limited potential for damage and because most of the time such small asteroids are too far away and therefore too faint to be detected with current techniques. Systematic searches for larger objects will continue to discover asteroids in this small size range when they venture close to the Earth.
Accordingly, the appropriate size range for a new survey for potentially hazardous asteroids is 200–300 meters to one kilometer.
STRATEGY FOR DISCOVERING AND CATALOGUING ASTEROIDS IN THE SIZE RANGE 200–300 METERS TO 1 KILOMETER
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In order to extend the ''Spaceguard Goal'' (90 percent completion in about 10 years of surveying) to a smaller size of 300 meters it is necessary to meet three requirements. First, it must be possible to reach a limiting visual magnitude of 24 according to the NRC report. Second, this limiting magnitude must be reached with a short exposure time (ideally less than 20 seconds). For fixed objects, it is possible to lengthen the exposure time in order to reach fainter limiting magnitudes; moving objects, such as PHAs, however, will move significantly during long exposures and will be more difficult to detect when their images are elongated. Third, it is necessary to survey a large area of the sky (several thousand square degrees) six times during each lunation in order to link the observations of any single asteroid and to derive a preliminary orbit.
Unlike the present Spaceguard Survey to about magnitude 19.5, this more ambitious survey cannot rely on amateur astronomers or other smaller observatories to follow up detections. Not only are such faint objects beyond the range of most other telescopes, but the sheer number of objects to be tracked becomes so great that every field imaged contains multiple objects requiring follow-up. Thus the only practical scheme is for the survey telescope to cover the entire sky multiple times per month, thereby providing the data both for discovery and for tracking and orbit determination. The National Optical Astronomy Observatory has funded a study to model the cadence required, optimum exposure times, and methods of prompt data processing.
The Large Synoptic Survey Telescope (LSST), recommended by name by the two NRC reports, is being designed to achieve these goals. It has a large aperture (8.3 m) and will reach V = 24 in 20 seconds; it has a wide field of view and can survey the entire visible sky in a few days; and it will be able to slew and settle quickly in order to maximize throughput. The community of interested scientists is developing a costed conceptual design for the LSST that will meet the goal of creating, over about a decade of observing, a catalog of PHAs that is about 90 percent complete down to diameters of 200–300 meters, with the exact details of completeness and limiting size to be determined after more detailed modeling of the predicted population of PHAs and of LSST performance.
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81931j.eps
STATEMENT SUBMITTED BY MARC SCHLATHER
PRESIDENT, PROSPACE
The Threat of Near-Earth Asteroids
On behalf of the members of ProSpace, I want to thank the committee for calling this hearing today and for inviting our organization to submit testimony. ProSpace has been working the issue of the NEO threat on Capitol Hill since our inception some eight years ago and are grateful that our work in this area has played some small part in raising the profile of this issue in Washington.
We particularly would like to acknowledge the work of Chairman Rohrabacher in this area. The most public expression of that work is the ''Charles 'Pete' Conrad Astronomy Awards Act of 2002'' which creates a prize for amateur astronomers who discover new near-Earth asteroids. ProSpace is a strong proponent of acknowledging the work of non-professionals in this area. As important, we believe the prize concept is one that we should be utilizing across a broad spectrum of space endeavors as a tool to invest in results rather than to directly fund all research. For both reasons ProSpace heartily endorses the approach put forward by the Chairman and commends it to the Congress for swift approval.
But his work to ameliorate the NEO threat goes far beyond this bill. Chairman Rohrabacher has been a vocal advocate of doing more to ameliorate the threat from Earth-crossing asteroids. This hearing is a good example of that work which we feel is vital to our future.
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Just why does ProSpace consider this subject is so important? To explain in part, let us go back in time to June 30, 1908. At just after 7:00 a.m. local time an object from space appears in the sky over western China and plunges through the atmosphere, glowing at a temperature of over 5,000 degrees. It heads over central Russia, producing a terrifying supersonic roar, preceded by a ballistic wave that levels trees and houses in its path.
At 7:17 a.m., upon reaching the area near the Stony Tunguska River at an altitude between two and nine kilometers above the ground, the object detonates with a force somewhere in the neighborhood of a 10 to 20 megaton nuclear explosion.
The resulting blast generates an area of devastation some 40 miles wide, two-thirds the area of Rhode Island. Because of the uninhabited nature of the region, few confirmed deaths are reported. It would have been a very different story if the object had impacted over a populated area of Europe instead of the Siberian outback. That little change might have resulted in as many as 500,000 deaths.
Why the history lesson? Because there is a very good chance this event was caused by an asteroid approximately 50–100 meters in diameter. And that just happens to be about the same size as the rock that passed within 75,000 miles of the Earth a few months back. No one saw that object, designated 2002 MN, until it had already passed us by.
We've seen the terrifying result of a large impact recently on one of our neighbors. In 1994, the world watched at Comet Shoemaker-Levy 9 broke up and crashed into the surface of the planet Jupiter with a force estimated to equal a billion megatons or more. The fireball created by the impact was larger in area than the Earth itself. The most alarming part of the Shoemaker-Levy 9 saga is that the comet was only discovered one year before impact.
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The purpose of sharing these stories is not to frighten but rather to focus your attention. Because if history teaches us anything, it is that the question is not whether an asteroid or comet is going to hit us. One will. Many will. Many have. More than 150 large impact craters have been located on the Earth's surface. In fact the impact scars on our planet would be as obvious as those you can see on the moon with your naked eye if it were not for the forces of natural erosion and geological events.
Among the real questions we must ask ourselves are when and where. We might get lucky again and see the impact come in an uninhabited area. But then again, we might not.
The most important question is, what can we do about it? There are three areas of concern we must address: search, warning and mitigation.
Before considering a series of specific actions and recommendations ProSpace believes are important, it would be useful to take a look at what we are currently doing—and that is regrettably little. On a challenge that could result in the death of thousands or millions or even the extinction of the human race, this nation is spending just under $4 million per year. The vast majority of those funds are devoted to looking for the so-called planet-killers, those objects of 1 kilometer in size and larger. Objects the size that caused the Tunguska devastation are not the subject of active search efforts and are only picked up by chance.
Virtually no search work is being done in the Southern Hemisphere. Much as we cannot see the Southern Cross constellation from the northern hemisphere, so too are there objects in the southern skies we are missing.
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Funding is of course an issue here. We do need to provide substantial new funding for search efforts, as well as other efforts as we will discuss shortly. But more than that, there is a fundamental paradigm shift needed in the way we look at our search efforts.
That is because we are talking about search and not research. The discovery, cataloguing and tracking of near-Earth objects is not sexy science. This is not the kind of work that results in an earth-shattering discovery by a scientist who then can publish his work in a peer journal and receive the accolades of his colleagues. It is essentially a mundane activity, looking into the skies each night and carefully logging the objects seen.
Add to that the fact that, when the Congress mandated that NASA create a program to find 90 percent of the large one-kilometer plus objects, it did so without an accompanying increase in NASA funding. The space agency was forced to fund the program out of existing science accounts, resulting in cutbacks in other research. At this point the science community that deals with NEO's remains concerned and convinced that a more robust search program mandated by the Congress will result in even more extensive cuts in other areas.
As important, it is vital that any new funding and facilities intended for search efforts be confined to those efforts. We must avoid any attempt by the scientific community to hijack new search assets for other research activities.
For those reasons we need to stop looking at NEO search as a science program and segregate those efforts from other endeavors. NEO search should be viewed as a national security concern and have its own Congressionally-provided funding stream.
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NEO Threat Identification and Mitigation: An Action Plan for the Future
To address this threat, we have consulted with recognized experts in the field, and have formulated recommendations in four specific areas.
Recommendation #1: Immediately Increase Funding for NEO Search Activities
A dramatic improvement in the rate at which asteroids are discovered would result if the United States were to increase the current level of funding, now at about $3.5 million per year, to $20 million in FY03. We recommend that Congress allocate such funding, over and above the President's request, as follows:
Increase Congressionally mandated search activities aimed at NEO's one kilometer in diameter and larger. Researchers estimate that only half of those have been located. In addition, current goals call for identifying just 90 percent of such objects within ten years, but of course any of the remaining undetected objects could have a catastrophic effect on Earth. Congress should direct NASA to continue the search for all such objects. Funding also should be provided for search activities in the Southern Hemisphere that will further increase the discovery rate.
Determine the best optical search methods to enable detection and tracking of smaller objects, such as 2002 MN. Such objects are not currently the targets of any formal search program. Rather, they are discovered as by-products of searches for larger objects. Since even one such impactor could destroy a major city and kill millions of people, we must begin looking for ways to identify objects at least down to 100 meters in diameter.
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Increase funding for the Minor Planet Center by $1 million annually: The MPC is responsible for the efficient collection, computation and dissemination of the characteristics and orbits of asteroids. It is the central international clearinghouse for tracking NEO's and must be funded at a level commensurate with its important mission.
Provide funding for more extensive follow-up observations: These efforts, which would include radar and spectroscopic observations, are vital for the refinement of asteroid orbits and determination of the object's general composition.
Recommendation #2: Create a Centralized Warning Center
One of the many challenges we face in dealing with the NEO threat is the absence of a central organization that has the authority and ability to:
Evaluate the threat potential of a particular object; and
Provide the necessary analysis and information to public agencies, both in the United States and overseas;
Respond quickly to actual impacts to reduce the possibility that the event could be misinterpreted as a nuclear attack.
We therefore recommend that Congress authorize the establishment of a centralized warning center facility under the authority of U.S. Space Command. Such a facility would accept technical, astronomical and environmental data about near-Earth asteroids and bolides and provide authoritative analysis to U.S. national leadership authorities in the event of a projected NEO impact event. Their analysis would allow senior U.S. civil and military authorities to develop appropriate responses in the event of an impact prediction.
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The analysis mission should include the determination of:
The probability that a particular NEO will strike Earth;
The likelihood that the object would penetrate Earth's atmosphere;
The potential damage from an impactor;
The best ways to disseminate this information so as to preclude misjudgments by other nations in response to an impact.
Additionally, the warning center will provide ''after the fact'' correlation of NEO impacts to minimize ''false positive'' warnings within the U.S. or regional military theaters.
Explosions from even small NEO impacts in the atmosphere, on the surface, or at sea could exacerbate existing tensions and escalate into a major international confrontation. For example, a short time ago, an El-Al pilot reported a missile fired at him from the ground while on a Tel Aviv-Moscow flight over Ukraine. He in fact had seen a small meteor.
Even more troubling was a recent atmospheric impact that produced a large, easily visible blast of light in the sky, at the same time that two nuclear-capable nations in Asia appeared on the verge of war. That high-altitude explosion occurred only a few hundred miles from the borders of the two countries and might have been mistaken for a nuclear attack by one on the other. We can and must reduce the potential for such miscalculation.
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Recommendation #3: Establish a Task Force to Develop and Coordinate Contingency Plans and Responses to Potential Impacts
Considering the nature of this NEO threat, some significant degree of contingency planning should be carried out by the United States regarding what can and should be done in advance of any impact and what can and should be done following one in response.
Should an unexpected or unavoidable impact occur on our territory or in a vital area of the globe, the United States must be able to identify the event as non-hostile, and be ready to respond to the needs of those affected by the disaster. Our reaction will require timely, accurate and secure exchanges of information between participants in the defense, emergency preparedness and scientific communities.
Therefore, we recommend that an Interagency Task Force be formed, composed of senior officials from: Department Of Homeland Security; Department of Defense; Department of State; NASA; FEMA; National Science Foundation; Office of Science and Technology Policy; and the National Research Council.
The Task Force would be charged with creating action and contingency plans for:
Emergency response to a possible impact, including diversion capabilities and civil defense preparation over the short- and long-term;
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Monitoring and analysis capabilities, robust enough to eliminate the possibility of misidentifying an impact as a nuclear attack;
Impact response scenarios, addressing the health, economic, and political effects on infrastructure and security;
NEO search technology upgrades and funding;
Initiation and formalization of international cooperation on NEO impact, search, and mitigation issues.
Recommendation #4: Advance a Vigorous Asteroid Exploration Program
We must begin research into methods and modalities of deflecting or destroying objects on a collision course with the Earth. We should be sending more unmanned probes to these objects now to learn more about them. We should be planning to send astronauts out to them as soon as we can develop the requisite technologies and vehicles. And we should be looking toward strategies to nudge these objects from their present orbit into one that will safely pass us by.
By visiting NEOs in our own ''neighborhood,'' we can sample their composition, determine their structure, and provide the facts essential to alleviating the threat. The knowledge gained from such missions will immeasurably assist in the creation of strategies and technologies for NEO deflection, should that become necessary.
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Conclusions
Each day that passes without an impact from a large object simply moves us closer to the day that does happen. If we had the ability to predict and prevent other natural disasters, such as earthquakes and hurricanes, we would. Why? Because we have in our lifetimes seen the destructive power of such events and the resulting costs in lives and damage.
Some have suggested that the way to get more attention for the danger NEO's present is to have a significant impact somewhere on the Earth. They contend that, as with September 11th, such an event would focus the attention of our leaders and the nation on the danger at hand. The problem with that suggestion is that one impact could kill thousands or even millions of people around the world. Or it might in fact end life as we know it, as it did in the time of the dinosaur.
This is an eventuality that we cannot accept, especially when it is in our power to work toward reducing the threat. There is an adage that goes, ''When did Noah build himself an ark? Before it rained!'' The time to take all of these steps is now, before the rain begins.
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(Footnote 1 return)
''Near-Earth Objects'' (NEOs) include asteroids and comets having an orbit with a closest approach to the Sun of less than 1.3 times that of the Earth (i.e., less than 120 million miles). Current NEO surveys focus primarily on Near-Earth Asteroids (NEAs). The terms ''NEO'' and ''NEA'' are thus often used interchangeably.
(Footnote 2 return)
Space Studies Board, National Research Council, Supporting Research and Data Analysis in NASA's Science Programs: Engines of Innovation and Synthesis, National Academy Press, Washington, D.C., 1998, pp. 48–50.
(Footnote 3 return)
Space Studies Board, National Research Council, Assessment of the Usefulness and Availability of NASA's Earth and Space Science Mission Data, National Academy Press, Washington, D.C., 2002, pp. 68–69.
(Footnote 4 return)
Board on Physics and Astronomy and Space Studies Board, National Research Council, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C., 2001.
(Footnote 5 return)
''Report of the Task Force on Potentially Hazardous Near-Earth Objects,'' British National Space Centre, September 2000. Page 16.
(Footnote 6 return)
''Astronomy and Astrophysics in the New Millennium,'' National Research Council, 2001. Page 10.
(Footnote 7 return)
''New Frontiers in the Solar System: An Integrated Exploration Strategy,'' NRC, 2002. Pages 380–382.