Full NRC Report! Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies: Final Report

Above are the links for both the Interim and the Just-Released Final Report.  Here are the Findings and Recommendations of the Final Report:

• Finding: Congress has mandated that NASA discover 90 percent of all near-Earth objects 140 meters in diameter or greater by 2020. The administration has not requested and Congress has not appropriated new funds to meet this objective. Only limited facilities are currently involved in this survey/discovery effort, funded by NASA’s existing budget.
• Finding: The current near-Earth object surveys cannot meet the goals of the 2005 George E. Brown, Jr. Near-Earth Object Survey Act directing NASA to discover 90 percent of all near-Earth objects 140 meters in diameter or greater by 2020.
• Finding: The selected approach to completing the George E. Brown, Jr. Near-Earth Object Survey will depend on nonscientific factors:
• If completion of the survey as close to the original 2020 deadline as possible is considered most important, a space mission conducted in concert with observations using a suitable ground-based telescope and selected by peer-reviewed competition is the best approach.
• This combination could complete the survey well before 2030, perhaps as early as 2022 if funding were appropriated quickly.
• If cost conservation is deemed most important, the use of a large ground-based telescope is the best approach. Under this option, the survey could not be completed by the original 2020 deadline, but could be completed before 2030. To achieve the intended cost effectiveness, the funding to construct the telescope must come largely on the basis of non-NEO programs.
• Recommendation: Because recent studies of meteor airbursts have suggested that near-Earth objects as small as 30 to 50 meters in diameter could be highly destructive, surveys should attempt to detect as many 30- to 50-meter objects as possible. This search for smaller-diameter objects should not be allowed to interfere with the survey for objects 140-meters in diameter or greater.
• Finding: The Arecibo and Goldstone radar systems play a unique role in the characterization of NEOs, providing unmatched accuracy in orbit determination, and insight into size, shape, surface structure, and other properties for objects within their latitude coverage and detection range.
• Recommendation: Immediate action is required to ensure the continued operation of the Arecibo Observatory at a level sufficient to maintain and staff the radar facility. Additionally, NASA and NSF should support a vigorous program of radar observations of NEOs at Arecibo and NASA should support such a program at Goldstone for orbit determination and characterization of physical properties.
• Recommendation: The United States should initiate a peer-reviewed, targeted research program in the area of impact hazard and mitigation of NEOs. Because this is a policy driven, applied program, it should not be in competition with basic scientific research programs or funded from them. This research program should encompass three principal task areas: surveys, characterization, and mitigation. The scope should include analysis, simulation, and laboratory experiments. This research program does not include mitigation space experiments or tests which are treated elsewhere in this report.
• Recommendation: The United States should take the lead in organizing and empowering a suitable international entity to participate in developing a detailed plan for dealing with the NEO hazard.
• Recommendation: Data from NEO airburst events observed by the U.S. Department of Defense satellites should be made available to the scientific community to allow it to improve understanding of the NEO hazards to Earth.
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• Finding: The mandated survey to locate 90 percent of near-Earth objects 140-meters in diameter or greater has not yet been funded by the federal government. Because the survey requires several years to budget and build new equipment, and then to conduct the search, completion by 2020 is not realistic.
• Finding: The selected approach to completing the George E. Brown, Jr. Near-Earth Object Survey will depend on nonscientific factors:
• • If completion of the survey as close to the original 2020 deadline as possible is considered most important, a space mission conducted in concert with observations using a suitable ground-based telescope and selected by peer-reviewed competition is the best approach. This combination could complete the survey well before 2030, perhaps as early as 2022 if funding were appropriated quickly.
• • If cost conservation is deemed most important, the use of a large ground-based telescope is the best approach. Under this option, the survey could not be completed by the original 2020 deadline, but could be completed before 2030. To achieve the intended cost-effectiveness, the funding to construct the telescope must come largely on the basis of non-NEO programs.
• Finding: It is highly probable that the next destructive NEO event will be an airburst from a <50- meter object, not a crater-forming impact.
• Recommendation: Because recent studies of meteor airbursts have suggested that near-Earth objects as small as 30 to 50 meters in diameter could be highly destructive, surveys should attempt to detect as many 30- to 50-meter objects as possible. This search for smaller-diameter objects should not be allowed to interfere with the survey for objects 140-meters in diameter or greater.
• Finding: The best opportunities for physical characterization of most NEOs occur during close Earth approaches when these objects are optically bright. Existing programs of ground-based optical observations for characterization of NEOs are few in number, and are not coordinated among different observing teams. Many observable NEOs are not characterized.
• Finding: The capabilities of Arecibo and Goldstone are complementary and many observing campaigns have utilized their synergy. One of the primary advantages of having two radar facilities is that one can serve as a backup for the other.
• Finding: The number of NEOs observed by radar per year could be increased about fivefold by obtaining sufficient observing time.
• Finding: Radar cannot be used to discover NEOs, but is a powerful tool for rapidly improving our knowledge of the orbit of a newly found object, and thus characterizing its potential hazard to Earth.
• Finding: The Arecibo and Goldstone radar systems play a unique role in the characterization of NEOs, providing unmatched accuracy in orbit determination, and insight into size, shape, surface structure, and other properties for objects within their latitude coverage and detection range.
• Finding: Congress has directed NASA to ensure that Arecibo is available for radar observations, but has not appropriated funds for this work.
• Recommendation: Immediate action is required to ensure the continued operation of the Arecibo Observatory at a level sufficient to maintain and staff the radar facility. Additionally, NASA and NSF should support a vigorous program of radar observations of NEOs at Arecibo and NASA should support such a program at Goldstone for orbit determination and characterization of physical properties.
• Finding: U.S. Department of Defense satellites have detected and continue to detect high-altitude airburst events from NEOs entering Earth’s atmosphere. Such data are valuable to the NEO community for assessing NEO hazards.
• Recommendation: Data from NEO airburst events observed by the U.S. Department of Defense satellites should be made available to the scientific community to allow it to improve understanding of the NEO hazards to Earth.
• Finding: Preliminary theoretical studies on low-altitude atmospheric Tunguska-like airbursts from asteroids as small as 30 meters in diameter suggest significant risk exists from these NEOs.
• Finding: Current models for generation of tsunamis by impacts into, or airbursts above, the ocean are not yet sufficiently reliable to establish threat levels to coastal communities.
• Recommendation: Additional observations and modeling should be performed to establish the risk associated with airbursts and with potential tsunami generation.
• Finding: Dedicated flyby spacecraft missions to NEOs provide only limited information relevant for hazard mitigation issues.
• Finding: Rendezvous spacecraft missions can provide detailed characterization of NEOs that could aid in the design and development of hazard-mitigation techniques. Such in situ characterization also allows calibration of ground- and space-based remote sensing data and may permit increased confidence in the use of remote classification of NEOs to inform future mitigation decisions.
• Recommendation: If NASA conducts human missions to NEOs, these missions should maximize the data obtained for NEO characterization.
• Finding: No single approach to mitigation is appropriate and adequate to fully prevent the effects of the full range of potential impactors, although civil defense is an appropriate component of mitigation in all cases. With adequate warning, a suite of four types of mitigation is adequate to mitigate the threat from nearly all NEOs except the most energetic ones.
• Finding: Civil defense (evacuation, sheltering in place, providing emergency infrastructure) is a cost-effective mitigation measure for saving lives from the smallest NEO impact events and is a necessary part of mitigation for larger events. If an NEO is predicted to impact on a specific, inhabited location, there is likely to be strong pressure for more than the most cost-effective method for saving lives.
• Finding: Slow-push-pull techniques are the most accurately controllable and are adequate for changing the orbits of small NEOs (tens of meters to roughly 100 m in diameter) with decades of advance warning and for somewhat larger NEOs (hundreds of meters) in those few cases where it would pass through a keyhole that would put the NEO onto an impact trajectory. Of the slow push/pull techniques, the gravity tractor appears to be the most independent of variations in the properties of the NEO and by far the closest to technological readiness.
• Finding: Kinetic impactors are adequate to prevent impacts on Earth by moderately sized NEOs (many hundreds of meters to 1 kilometer) with decades of advance warning. The concept has been demonstrated in space, but the result is sensitive to the properties of the NEO and requires further study.
• Finding: Unless a large flotilla (100 or more) of massive spacecraft was sent as impactors, nuclear explosions are the only current, practical means for changing the orbit of large NEOs (diameters greater than about 1 km). They also remain as a backup strategy for somewhat smaller objects if other methods have failed. They may be the only method for dealing with smaller objects when warning time is short, but additional research is necessary for these cases.
• Finding: For a wide range of impact scenarios, launch capability exists to deliver an appropriate payload to mitigate an NEO. For some scenarios, particularly short warning scenarios, the capability is inadequate. Development of foreseen heavy-lift launch vehicles, such as the Ares cargo vehicle, should enable the use of a variety of methods for NEOs up to 2 times larger than is possible with current launch vehicles
• Finding: Mitigation of the threat from NEOs benefits dramatically from in-situ characterization of the NEO prior to mitigation, if there is time to do so.
• Finding: Changing the orbit of an NEO with our current understanding is sufficiently uncertain that, in most cases, it requires an accompanying verification. This is easy to implement with many slow-push techniques but requires considerable additional effort for other techniques.
• Recommendation: If Congress chooses to fund mitigation research at an appropriately high level, the first priority for a space mission in the mitigation area is an experimental test of a kinetic impactor along with a characterization, monitoring and verification system, such as the Don Quijote mission that was previously considered, but not funded, by ESA. This mission would produce the most significant advances in understanding and provide an ideal chance for international collaboration in a realistic mitigation scenario.
• Recommendation: The United States should initiate a peer-reviewed, targeted research program in the area of impact hazard and mitigation of NEOs. Because this is a policy driven, applied program, it should not be in competition with basic scientific research programs or funded from them. This research program should encompass three principal task areas: surveys, characterization, and mitigation. The scope should include analysis, simulation, and laboratory experiments. This research program does not include mitigation space experiments or tests which are treated elsewhere in this report.
• Recommendation: The United States should establish a standing committee with membership from each of the relevant agencies and departments, to develop a detailed plan for treating all aspects of the threat posed to Earth by NEOs, and apportioning among these agencies and departments authority and responsibility for carrying out this plan, in coordination and collaboration with other nations. The committee would be further charged with overseeing on a continuing basis the carrying out of each agency’s and department’s activities under this plan. The Administration should designate one agency or department as the lead; the chair of the committee should be the representative from this agency or department.
• Recommendation: The United States should take the lead in organizing and empowering a suitable international entity to participate in developing a detailed plan for dealing with the NEO hazard.
• Finding: A $10 million annual level of funding would be sufficient to continue existing surveys, maintain the radar capability at the Arecibo and Goldstone observatories, and support a modest level of research on the hazards posed by NEOs. This level would not allow achievement of the goals established in the George E. Brown, Jr. Near-Earth Object Survey Act on any timescale. A $50 million annual level of funding for several years would likely be sufficient to achieve the goals of the George E. Brown, Jr. Near-Earth Object Survey Act. A $250 million annual level of funding if continued for somewhat under a decade, would be sufficient to accomplish the survey and research objectives, plus provide survey redundancy and support for a space mission to test in situ characterization and mitigation.