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The term Spaceguard loosely refers to a number of efforts to discover and study near-Earth objects (NEO). Asteroids are discovered by telescopes which repeatedly survey large areas of sky. Efforts which concentrate on discovering NEOs are considered part of the "Spaceguard Survey," regardless of which organization they are affiliated with. A number of organizations have also raised related discussions and proposals on asteroid-impact avoidance. == History == Arthur C. Clarke coined the term in his novel ''Rendezvous with Rama'' (1972) where SPACEGUARD was the name of an early warning system created following a catastrophic asteroid impact.〔Michael Paine (2000-04-26), ("Bigger Telescopes Seek Killer Asteroids" ), ''Space.com'' (accessed on 2010-06-26)〕 This name was later adopted by a number of real life efforts to discover and study near-Earth objects. A 1992 US Congressional study produced a "Spaceguard Survey Report"〔David Morrison (1992), "(The Spaceguard Survey Report )", ''(NASA Studies )'' at Asteroid and Comet Impact Hazards, NASA Ames Research Center.〕 which led to a mandate that NASA locate 90% of near-Earth asteroids larger than 1 km within 10 years. This is often referred to as the "Spaceguard Goal." A number of efforts which receive money through NASA are all considered to be working on the "Spaceguard Project." The impact of Comet Shoemaker–Levy 9 to Jupiter in July 1994 created a greater perception of importance to the detection of near Earth objects. As David Levy stated in an interview "The giggle factor disappeared after Shoemaker-Levy 9." He was referring to the contemporary attitude that extinction level events were so improbable that those advocating for research for detection and possible deflection methods were only paranoid alarmists. The impact of one of its fragments created a giant dark spot over 12,000 km across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT (600 times the world's nuclear arsenal). After the impact of Comet Shoemaker-Levy 9, asteroid detection programs all over the world received greater funding. The Working Group on Near-Earth Objects (WGNEO) of the International Astronomical Union held a workshop in 1995 entitled ''Beginning the Spaceguard Survey''〔(Beginning the Spaceguard Survey ), Vulcano Workshop (1995), IAU Working Group on Near-Earth Objects. (accessed on 2010-06-26)〕 which led to an international organization called the Spaceguard Foundation. Subsequently there have been Spaceguard associations or foundations formed in countries around the world to support the ideas of discovering and studying near-Earth objects. Generally, the Spaceguard organizations formed within individual countries are associated with the international foundation or with the NASA efforts only by name, common interests, and similar goals. The initial Spaceguard Goal was achieved, although in slightly longer than 10 years. An extension to the project gave NASA the mandate of reducing the minimum size at which more than 90% of near-Earth asteroids are known to 140 m.〔Harris, Alan. ( What Spaceguard did ), ''Nature, Vol. 453, pp. 1178-1179, June 26, 2008, DOI:10.1038/4531178a; Published online 25 June 2008 (subscription).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「spaceguard」の詳細全文を読む スポンサード リンク
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