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188-001BNSC NEO FC/IFC/IBC/BC 5/9/00 3:16 pm Page 2 Report of the Task Force on potentially hazardous NEAR EARTH OBJECTS 188-001BNSC NEO FC/IFC/IBC/BC 5/9/00 3:16 pm Page 3 Cover (front and back) SOLAR SYSTEM showing the Sun, the planets, the main belt of asteroids and the orbit of a typical comet (drawing not to scale). The planets are, counting from the Sun: Mercury, Venus, Earth, Mars (to the left), the giant planet Jupiter (to the right) and Saturn (top left, back cover). The comet, coming from the far reaches of the Solar System, is shown in two positions along its orbit. The comet’s tail always points directly away from the Sun. The belt of asteroids contains about one million objects over 1kilometre in size. Some asteroids are deflected by Jupiter’s gravitational field to become Near Earth Objects. A stony asteroid is shown at the bottom of the cover; it is covered with small craters by the impact of other asteroids over the ages. Inside front and back covers Asteroid and comet impact craters on far side of Moon. Title page Moon impact craters (bottom) and Earth (top) photographed from US Clementine spacecraft 1994. *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 1 NASA Report of the Task Force on potentially hazardous Near Earth Objects September 2000 *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 3 CONTENTS List of Graphs, Tables Chapter 7 and Illustrations 4 Activities in Britain 27 Terms of Reference Chapter 8 and Membership of Task Force 5 Mitigation possibilities 28 Acknowledgements 5 Chapter 9 What is to be done? Executive Summary 6 including recommendations 30 Summary of Annex A Recommendations 7 Chronology 36 Chapter 1 Annex B Introduction 9 Impacts and Close Approaches of Asteroids Chapter 2 and Comets 39 Asteroids, Comets and Near Earth Objects 11 Annex C Ground-based Telescopes Chapter 3 and Radars 43 Environmental Effects on Earth 15 Annex D Space-based Missions 46 Chapter 4 Overall Risk 20 Glossary 49 Chapter 5 Bibliography (and websites) 51 Observational Techniques 22 Acknowledgements Chapter 6 for Illustrations 54 Current Activities and Future Plans 24 3 *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 4 LIST OF GRAPHS, TABLES & ILLUSTRATIONS Graphs Comet Hale-Bopp above Stonehenge Numbers of near Earth asteroids by size (Chapter 2) (Chapter 2) Orbits of Halley’s comet and Hale-Bopp Frequency of impacts of near Earth asteroids (Chapter 2) by size (Chapter 3) Sources of long and short period comets (Chapter 2) Tables Comet Shoemaker-Levy 9 hitting Jupiter, 1994 Impact effects by size of Near Earth Object (Chapter 3) (Chapter 3) Asteroid and comet impact craters on Moon Estimated fatalities for wide variety of different (Chapter 3) impact scenarios (Chapter 4) Tsunami from Eltanin impact, Illustrations South East Pacific Solar System (Cover) (Chapter 3) Asteroid and comet impact craters on Moon Clearwater Lakes, Quebec, formed from twin (Inside front and back covers) impact craters (Chapter 3) Moon craters and Earth (Title page) Asteroid seen by movement against fixed stars Orbits of all known near Earth asteroids (Chapter 5) (Chapter 1) LINEAR Survey Telescope, New Mexico Barringer Crater,Arizona (Chapter 6) (Chapter 1) United Kingdom Schmidt Telescope,Australia Asteroid Eros from orbiting spacecraft (Chapter 7) (Chapter 2) NASA’s Deep Impact mission to hit comet Orbits of asteroids Aten,Apollo and Amor (Chapter 8) (Chapter 2) Asteroid belt within Jupiter’s orbit (Chapter 2) 4 *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 5 TERMS OF REFERENCE AND MEMBERSHIP OF TASK FORCE On 4 January 2000 the Minister for Science, Lord to take in the light of 1 and 2 above and on Sainsbury, announced the setting up of a Task Force the communication of issues to the public; and on Potentially Hazardous Near Earth Objects to report to the Director General of the (NEOs). British National Space Centre (BNSC) by the The Task Force was invited to make proposals to middle of 2000. the Government on how the United Kingdom The Task Force was chaired by Dr Harry Atkinson should best contribute to international effort on with Sir Crispin Tickell and Professor David Near Earth Objects; and to Williams as members. 1. confirm the nature of the hazard and potential The British National Space Centre provided the levels of risk; Secretary, Richard Tremayne-Smith, and general 2. identify the current UK contribution to support.The Task Force met on a number of international efforts; occasions and presented its Report to the Director General of the British National Space Centre in 3. advise the Government on what further action August 2000. ACKNOWLEDGEMENTS The Task Force has been supported by the British Ben Atkinson, Jim Beletic,Andrea Boattini, Roger National Space Centre; and has been helped greatly Bonnet, Giacomo Cavallo, Catherine Cesarsky, by many people in the United Kingdom, in Europe, Moustafa Chahine,Andrew Cheng, Paul Chodas, the United States and in other countries.We cannot Victor Clube, Marcello Coradini, Ian Corbett, David hope to name them all. Crichton, Len Culhane, David Dale,Vernon J Ehlers, Jim Emerson,Walter Flury, Bob Fosbury, Simon However, our particular thanks go to the following French, Iain Gilmour, Monica Grady, Robert people who have made substantial contributions to Hawley, Eleanor Helin, Jeremy Hodge, Ken our understanding of the subject and in other ways: Hodgkins, John Houghton, David Hughes, Julian Johannes Anderson, Mark Bailey,Andrea Carusi, Hunt, Raymond Hyde, Syuzo Isobe, Lindley Alan Fitzsimmons,Tom Gehrels,Alan Harris, Johnson,Adrian Jones, Patrick Laycock, Jean Le Nigel Holloway, Brian Marsden,Tony Mayer, Guen, Robert MacMillan,Vittorio Manno, Neil David Morrison, Paul Murdin, Martin Rees, McBride, Craig McKay, Duncan Moore, Patrick Hans Richter, Jay Tate, Richard West, Iwan Williams, Moore,Tom Morgan,Ian Morison, Richard Pete Worden, Don Yeomans;and a special thanks to Oberman, Ron Oxburgh, Lembit Öpik,Vernon Duncan Steel for suggesting many of the illustrations Pankokin, Carl Pilcher, Klaus Pinkau, John Ponsonby, and in other ways. Steven Pravdo, David Price,Antonio Rodotà, Michael Schultz, John Schumacher, Geoff Sommers, In addition, the following have much helped us: Hugh Van Horn,Victor Vilhard, Dan Weedman, Michael A’Hearn, Morris Aizenman, David Asher, Chandra Wickramasinghe, John Zarnecki. 5 *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 6 ExecutiveEXECUTIVE summarySUMMARY normous numbers of asteroids and comets bring them near to the Earth.With greater orbit the Sun. Only a tiny fraction of information about them, fairly accurate predictions them follow paths that bring them near can be made.The risk from comets is between 10 the Earth. These Near Earth Objects and 30 per cent of that from asteroids.The advance rangeE in size from pebbles to mountains, and travel at warning period for a potential impact from a long high speeds. period comet may be as short as a year compared to Such objects have collided with the Earth since its decades or centuries for asteroids. Short period formation, and brought the carbon and water which comets can be considered along with asteroids. made life possible.They have also caused widespread The threat from Near Earth Objects raises major changes in the Earth’s surface, and occasional issues, among them the inadequacy of current extinctions of such living organisms as the dinosaurs. knowledge, confirmation of hazard after initial The threat has only recently been recognised and observation, disaster management (if the worst accepted.This has come about through advances in came to the worst), methods of mitigation telescope technology allowing the study of these including deflection, and reliable communication usually faint objects, the identification of craters on with the public.The Task Force believes that steps the moon, other planets and the Earth as a result of should be taken at government level to set in place impacts, and the dramatic collision of pieces of the appropriate bodies – international, European comet Shoemaker-Levy 9 with Jupiter in 1994. including national – where these issues can be Impacts represent a significant risk to human and discussed and decisions taken.The United other forms of life. Means now exist to mitigate the Kingdom is well placed to make a significant consequences of such impacts for the human species. contribution to what should be a global effort. The largest uncertainty in risk analysis arises from The recommendations of the Task Force are given our incomplete knowledge of asteroids whose orbits with supporting arguments in Chapter 9. 6 *188-001 NEO Task FINAL a 5/9/00 3:17 pm Page 7 SummarySUMMARY OF of recommendationRECOMMENDATIONSs ecommendations 1 to 9 cover the Accurate orbit United Kingdom’s scientific role determination within an international effort and Recommendations 10 to 14 the Recommendation 4 We recommend that the 1 metre Johannes Kapteyn coordinationR of all aspects of the subject Telescope on La Palma, in which the United Kingdom internationally, in Europe and in Britain. is a partner, be dedicated to follow-up observations of Near Earth Objects. Survey and discovery of Near Earth Objects Composition and Recommendation 1 gross properties We recommend that the Government should seek Recommendation 5 partners, preferably in Europe, to build in the We recommend that negotiations take place with the southern hemisphere an advanced new 3 metre-class partners with whom the United Kingdom shares survey telescope for surveying substantially smaller suitable telescopes to establish an arrangement for objects than those now systematically observed by small amounts of time to be provided under other telescopes. The telescope should be dedicated to appropriate financial terms for spectroscopic follow- work on Near Earth Objects and be located on an up of Near Earth Objects.
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  • Detecting the Yarkovsky Effect Among Near-Earth Asteroids From

    Detecting the Yarkovsky Effect Among Near-Earth Asteroids From

    Detecting the Yarkovsky effect among near-Earth asteroids from astrometric data Alessio Del Vignaa,b, Laura Faggiolid, Andrea Milania, Federica Spotoc, Davide Farnocchiae, Benoit Carryf aDipartimento di Matematica, Universit`adi Pisa, Largo Bruno Pontecorvo 5, Pisa, Italy bSpace Dynamics Services s.r.l., via Mario Giuntini, Navacchio di Cascina, Pisa, Italy cIMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, Univ. Lille, 77 av. Denfert-Rochereau F-75014 Paris, France dESA SSA-NEO Coordination Centre, Largo Galileo Galilei, 1, 00044 Frascati (RM), Italy eJet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, Pasadena, 91109 CA, USA fUniversit´eCˆote d’Azur, Observatoire de la Cˆote d’Azur, CNRS, Laboratoire Lagrange, Boulevard de l’Observatoire, Nice, France Abstract We present an updated set of near-Earth asteroids with a Yarkovsky-related semi- major axis drift detected from the orbital fit to the astrometry. We find 87 reliable detections after filtering for the signal-to-noise ratio of the Yarkovsky drift esti- mate and making sure the estimate is compatible with the physical properties of the analyzed object. Furthermore, we find a list of 24 marginally significant detec- tions, for which future astrometry could result in a Yarkovsky detection. A further outcome of the filtering procedure is a list of detections that we consider spurious because unrealistic or not explicable with the Yarkovsky effect. Among the smallest asteroids of our sample, we determined four detections of solar radiation pressure, in addition to the Yarkovsky effect. As the data volume increases in the near fu- ture, our goal is to develop methods to generate very long lists of asteroids with reliably detected Yarkovsky effect, with limited amounts of case by case specific adjustments.