From: House Committee on Science, Space, and Technology
Posted: Thursday, October 3, 2002
Thursday, October 3, 2002 10:00 a.m. 2318 Rayburn House Office Building
1.Purpose of Hearing
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.
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.
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 $3.5 M in FY2001 and an additional $3.5 M in FY2002 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.
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 aresponse 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)?
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.
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.
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.
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?
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 NEOobservations? 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?
Figure 1 Threat of Near-Earth Asteroids
This chart does not reflect a growing number of asteroids but rather a growth in the number that we are aware of due to the discoveries of recent NEO survey activities.
 "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.
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