WASHINGTON -- A new report from the National Research Council lays out options NASA could follow to detect more near-Earth objects (NEOs) – asteroids and comets that could pose a hazard if they cross Earth's orbit. The report says the $4 million the U.S. spends annually to search for NEOs is insufficient to meet a congressionally mandated requirement to detect NEOs that could threaten Earth. Congress mandated in 2005 that NASA discover 90 percent of NEOs whose diameter is 140 meters or greater by 2020, and asked the National Research Council in 2008 to form a committee to determine the optimum approach to doing so.  In an interim report released last year, the committee concluded that it was impossible for NASA to meet that goal, since Congress has not appropriated new funds for the survey nor has the administration asked for them.  In its final report, the committee lays out two approaches that would allow NASA to complete its goal soon after the 2020 deadline; the approach chosen would depend on the priority policymakers attach to spotting NEOs.  If finishing NASA's survey as close as possible to the original 2020 deadline is considered most important, a mission using a space-based telescope conducted in concert with observations from a suitable ground-based telescope is the best approach, the report says.  If conserving costs is deemed most important, the use of a ground-based telescope only is preferable.  The report also recommends that NASA monitor for smaller objects – those down to 30 to 50 meters in diameter -- which recent research suggests can be highly destructive.  However, the report stresses that searching for smaller objects should not interfere with first fulfilling the mandate from Congress.  Beyond completion of that mandate, the report notes the need for constant vigilance in monitoring the skies, so as to detect all dangerous NEOs.  In addition, the nation should undertake a peer-reviewed research program to better investigate the many unknown aspects connected with detecting NEOs and countering those that could be a threat.  The U.S. should also take the lead in organizing an international entity to develop a detailed plan for dealing with hazards from these objects. In addition, the report recommends that immediate action be taken to ensure the continued operation of the Arecibo Observatory in Puerto Rico.  NASA and NSF should support a vigorous program of NEO observations at Arecibo, and NASA should also support such a program at the Goldstone Deep Space Communications Complex.  Although these facilities cannot discover NEOs, they play an important role in accurately determining the orbits and characterizing the properties of NEOs within radar range. THE SCOPE OF THE HAZARD
 Near-Earth objects are asteroids and comets that orbit the sun and approach or cross Earth's orbit.  An asteroid or comet about 10 kilometers in diameter struck the Yucatan peninsula 65 million years ago and caused global devastation, probably wiping out large numbers of plant and animal species including the dinosaurs.  Objects as large as this one strike Earth only about once every 100 million years on average, the report notes.  NASA has been highly successful at detecting and tracking objects 1 kilometer in diameter or larger, and continues to search for these large objects. Objects down to sizes of about 140 meters in diameter -- which NASA has been mandated to survey for -- would cause regional damage; such impacts happen on average every 30,000 years, the report says. While impacts by large NEOs are rare, a single impact could inflict extreme damage, raising the classic problem of how to confront a possibility that is both very rare and very important.  Far more likely are those impacts that cause only moderate damage and few fatalities.  Conducting surveys for NEOs and detailed studies of ways to mitigate collisions is best viewed as a form of insurance, the report says.  How much to spend on these insurance premiums is a decision that must be made by the nation's policymakers. MITIGATING DAMAGE
 The report also examines what is known about methods to defend against NEOs.  These methods are new and still immature.  No single approach is effective for the full range of near-Earth objects, the committee concluded.  But with sufficient warning, a suite of four types of mitigation is adequate to meet the threat from all NEOs, except the most energetic ones.  

• 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.
• "Slow push" or "slow pull" methods use a spacecraft to exert force on the target object to gradually change its orbit to avoid collision with the Earth.  This technique is practical only for small NEOs (tens of meters to roughly 100 meters in diameter) or possibly for medium-sized objects (hundreds of meters), but would likely require decades of warning.  Of the slow push/pull techniques, the gravity tractor appears to be by far the closest to technological readiness.
•  Kinetic methods, which fly a spacecraft into the NEO to change its orbit, could defend against moderately sized objects (many hundreds of meters to 1 kilometer in diameter), but also may require decades of warning time. 
• Nuclear explosions are the only current, practical means for dealing with large NEOs (diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail.   

Although all of these methods are conceptually valid, none is now ready to implement on short notice, the report says.  Civil defense and kinetic impactors are probably the closest to readiness, but even these require additional study prior to reliance on them.  Given the significant unknowns about many aspects of the threat and its mitigation, the report recommends that the U.S. start a peer-reviewed, targeted research program on the hazards posed by NEOs, and how to deal with them.  Because this is a policy-driven, applied research program, it should not be in competition with basic scientific research programs or be funded from them, the report adds.    The study was sponsored by NASA at the request of Congress.  The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter.  The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.  A committee roster follows.                                                                                                                                                                                                                      Copies of DEFENDING PLANET EARTH: NEAR-EARTH OBJECT SURVEYS AND HAZARD MITIGATION STRATEGIES are available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at HTTP://WWW.NAP.EDU.   Reporters may obtain a copy from the Office of News and Public Information (contacts listed above). 
Contacts: Sara Frueh, Media Relations Officer
Alison Burnette, Media Relations Assistant
National Research Council
202-334-2138; e-mail news@nas.edu NATIONAL RESEARCH COUNCILDivision on Engineering and Physical SciencesAeronautics and Space Engineering BoardSpace Studies Board COMMITTEE TO REVIEW NEAR-EARTH OBJECT SURVEYS AND HAZARD MITIGATION STRATEGIES STEERING COMMITTEE IRWIN I. SHAPIRO1 (CHAIR)Timken University ProfessorHarvard University; andSenior Smithsonian ScientistHarvard-Smithsonian Center for AstrophysicsCambridge, Mass. MICHAEL A'HEARN (VICE CHAIR)ProfessorDepartment of AstronomyUniversity of MarylandCollege Park FAITH VILAS (VICE CHAIR)DirectorMMT ObservatoryMt. Hopkins, Ariz. ANDREW F. CHENGChief ScientistSpace DepartmentApplied Physics LaboratoryJohns Hopkins UniversityLaurel, Md. FRANK CULBERTSON JR.Senior Vice PresidentOrbital Sciences Corp.Dulles, Va. DAVID C. JEWITT1ProfessorDepartment of Earth and Space Sciences, andInstitute for Geophysics and Planetary PhysicsUniversity of CaliforniaLos Angeles STEPHEN MACKWELLDirectorLunar and Planetary InstituteHouston H. JAY MELOSH1University Distinguished ProfessorPurdue UniversityWest Lafayette, Ind. JOSEPH H. ROTHENBERGPresidentUniversal Space NetworkDarnestown, Md. SURVEY/DETECTION PANEL FAITH VILAS (CHAIR)DirectorMMT ObservatoryMt. Hopkins, Ariz. PAUL ABELLResearch ScientistPlanetary Science InstituteHouston ROBERT F. ARENTZNew Business ManagerBall Aerospace and Technologies Corp.Boulder, Colo. LANCE A.M. BENNERResearch ScientistJet Propulsion LaboratoryPasadena, Calif. WILLIAM F. BOTTKEAssistant DirectorDepartment of Space StudiesSouthwest Research InstituteBoulder, Colo. WILLIAM E. BURROWSIndependent Aerospace Writer and HistorianStamford, Conn. ANDREW F. CHENGChief ScientistSpace DepartmentApplied Physics LaboratoryJohns Hopkins UniversityLaurel, Md. ROBERT D. CULPProfessorDepartment of Aerospace Engineering SciencesUniversity of ColoradoBoulder YANGA FERNANDEZAssistant Professor of Planetary Science/AstronomyDepartment of PhysicsUniversity of Central FloridaOrlando LYNNE JONESLLST FellowDepartment of AstronomyUniversity of WashingtonSeattle STEPHEN MACKWELLDirectorLunar and Planetary InstituteHouston AMY MAINZERResearch ScientistJet Propulsion LaboratoryPasadena, Calif. GORDON H. PETTENGILL1Professor of Planetary PhysicsDepartment of Earth, Atmospheric, and Planetary SciencesMassachusetts Institute of TechnologyCambridge JOHN RICEProfessorDepartment of StatisticsUniversity of CaliforniaBerkeley MITIGATION PANEL MICHAEL A'HEARN (CHAIR)ProfessorDepartment of AstronomyUniversity of MarylandCollege Park MICHAEL J.S. BELTOMPresident and Deputy Principal InvestigatorBelton Space Exploration Initiatives LLCTucson, Ariz. MARK BOSLOUGHPrincipal MemberExploratory Simulation Technologies DepartmentSandia National LaboratoriesAlbuquerque, N.M. CLARK R. CHAPMANSenior ScientistDepartment of Space StudiesSouthwest Research InstituteBoulder, Colo. SIGRID CLOSEAssistant ProfessorDepartment of Aeronautics and AstronauticsStanford UniversityStanford, Calif. JAMES A. DATORDirectorHawaii Research Center for Future StudiesDepartment of Political SciencesUniversity of HawaiiManoa DAVID S.P. DEARBORNResearch ScientistLawrence Livermore National LaboratoryLivermore, Calif. KEITH A. HOLSAPPLEProfessorAeronautics and Astronautics DepartmentUniversity of WashingtonSeattle DAVID Y. KUSNIERKIEWICZChief EngineerSpace DepartmentApplied Physics LaboratoryJohns Hopkins UniversityMcLean, Va. PAULO LOZANOCharles Stark Draper Assistant Professor
of Aeronautics and AstronauticsDepartment of Aeronautics and AstronauticsMassachusetts Institute of TechnologyCambridge EDWARD D. MCCULLOUGHPrincipal Scientist Boeing (RETIRED)Riverside, Calif. H. JAY MELOSH1University Distinguished ProfessorPurdue UniversityWest Lafayette, Ind. DAVID J. NASH2PresidentDave Nash & Associates LLCBirmingham, Ala. DANIEL J. SCHEERESProfessorDepartment of Aerospace Engineering SciencesColorado Center for Astrodynamics ResearchUniversity of ColoradoBoulder SARAH T. STEWART-MUKHOPADHYAYJohn L. Loeb Associate Professor of the
Natural SciencesDepartment of Earth and Planetary SciencesHarvard UniversityCambridge KATHRYN C. THORNTONAssociate DeanDepartment of Science, Technology, and
SocietyUniversity of VirginiaCharlottesville RESEARCH COUNCIL STAFF DWAYNE A. DAYStudy Co-Director PAUL JACKSONStudy Co-Director                                                                       1 Member, National Academy of Sciences2 Member, National Academy of Engineering