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USA-214, known before launch as Advanced Extremely High Frequency 1 or AEHF SV-1, is a military communications satellite operated by the United States Air Force. It is the first of four spacecraft to be launched as part of the Advanced Extremely High Frequency program, which will replace the earlier Milstar system.〔(【引用サイトリンク】title=Atlas V AEHF-1 Mission Overview )〕 The USA-214 spacecraft was constructed by Lockheed Martin, and is based on the A2100 satellite bus. The spacecraft has a mass of and a design life of 14 years. It will be used to provide super high frequency and extremely high frequency communications for the armed forces of the United States, as well as those of the United Kingdom, the Netherlands, and Canada.〔 ==Launch and orbital insertion== USA-214 was launched by United Launch Alliance, using an Atlas V 531 carrier rocket flying from Space Launch Complex 41 at the Cape Canaveral Air Force Station. The launch occurred at 11:07 UTC on 14 August 2010, and resulted in the spacecraft being deployed successfully into a geosynchronous transfer orbit with a perigee of , an apogee of , and 22.2° degrees inclination. The spacecraft was intended to manoeuvre from the transfer orbit into which it was launched to its operational geosynchronous orbit by means of a Liquid Apogee Engine (LAE) and several Hall effect thrusters, a process which normally takes 105 days. However, the satellite's Liquid Apogee Engine malfunctioned shortly after ignition on both its first burn on 15 August 2010 and a second attempt on 17 August,〔Ray, Justin (Sept. 2, 2010), ''Spaceflight Now'', "(Investigators probing what went wrong with AEHF 1 )" (accessed Dec. 14, 2011)〕 and it was declared inoperable.〔〔(【引用サイトリンク】url=http://spaceflightnow.com/atlas/av019/101019aehf2.html )〕 To solve the problem, the perigee altitude was raised to 4700 km (2900 miles) using twelve firings of the smaller Reaction Engine Assembly thrusters, originally intended for attitude control during LAE maneuvers.〔Ray, Justin (October 9, 2011), ''Spaceflight Now'', "(Air Force satellite's epic ascent should finish soon )" (accessed Dec. 14 2011)〕 From this altitude, the solar arrays were deployed and the orbit was raised toward the operational orbit over the course of nine months using the 0.27 Newton Hall thrusters, a form of electric propulsion which is highly efficient, but produces very low thrust. 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「USA-214」の詳細全文を読む スポンサード リンク
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