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Project Vanguard was a program managed by the United States Naval Research Laboratory (NRL), which intended to launch the first artificial satellite into Earth orbit using a Vanguard rocket〔( "The Vanguard Satellite Launching Vehicle — An Engineering Summary". B. Klawans. April 1960, 212 pages. ) Martin Company Engineering Report No 11022, PDF of an optical copy.〕 as the launch vehicle from Cape Canaveral Missile Annex, Florida. In response to the surprise launch of ''Sputnik 1'' on October 4, 1957, the U.S. restarted the Explorer program, which had been proposed earlier by the Army Ballistic Missile Agency (ABMA). Privately, however, the CIA and President Dwight D. Eisenhower were aware of progress being made by the Soviets on Sputnik from secret spy plane imagery.〔PBS.org - NOVA:Sputnik Declassified〕 Together with the Jet Propulsion Laboratory (JPL), ABMA built ''Explorer 1'' and launched it on January 31, 1958. Before work was completed, however, the Soviet Union launched a second satellite, ''Sputnik 2'', on November 3, 1957. Meanwhile, the spectacular televised failure of ''Vanguard TV3'' on December 6, 1957 deepened American dismay over the country's position in the Space Race. On March 17, 1958, ''Vanguard 1'' became the second artificial satellite successfully placed in Earth orbit by the United States. It was the first solar-powered satellite. Just 152 mm (6 in) in diameter and weighing just 1.4 kg (3 lb), ''Vanguard 1'' was described by then-Soviet Premier Nikita Khrushchev as, "The grapefruit satellite."〔 (【引用サイトリンク】 Vanguard I - the World's Oldest Satellite Still in Orbit )〕 ''Vanguard 1'' is the oldest artificial satellite still in space, as Vanguard's predecessors, ''Sputnik 1'', ''Sputnik 2'', and ''Explorer 1'', have decayed from orbit. == Project history == In the early 1950s, the American Rocket Society set up an ad hoc Committee on Space Flight, of which Milton W. Rosen, NRL project manager for the Viking rocket, became chair. Encouraged by conversations between Richard W. Porter of General Electric and Alan T. Waterman, Director of the National Science Foundation (NSF), Rosen on November 27, 1954 completed a report describing the potential value of launching an earth satellite. The report was submitted to the NSF early in 1955.〔( ''Vanguard — A History'', Chapter 1. Constance M. Green and Milton Lomask, NASA SP-4202. NASA Historical Reference Collection, NASA History Office, NASA Headquarters, Washington, DC. and http://www.hq.nasa.gov/office/pao/History/SP-4202/begin.html )〕 As part of planning for the International Geophysical Year (IGY) (1957–1958), the U.S. publicly undertook to place an artificial satellite with a scientific experiment into orbit around the Earth. 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「Project Vanguard」の詳細全文を読む スポンサード リンク
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