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Vanguard 2 or Vanguard II is an Earth-orbiting satellite launched February 17, 1959, aboard a Vanguard SLV 4 rocket as part of the United States Navy's Project Vanguard.〔(【引用サイトリンク】 VANGUARD - A HISTORY, CHAPTER 12, SUCCESS - AND AFTER )〕 The satellite was designed to measure cloud-cover distribution over the daylight portion of its orbit, for a period of 19 days, and to provide information on the density of the atmosphere for the lifetime of its orbit (about 300 years). As of July 21, 2015, Vanguard 2 was still in orbit. ==Design== The spacecraft is a magnesium sphere 20 in (50.8 cm) in diameter. It contained two optical telescopes with two photocells. The sphere was internally gold-plated, and externally covered with an aluminum deposit coated with silicon oxide of sufficient thickness to provide thermal control for the instrumentation. Radio communication was provided by a 1 W, 108.03 MHz telemetry transmitter and a 10 mW, 108 MHz beacon transmitter that sent a continuous signal for tracking purposes. A command receiver was used to activate a tape recorder that relayed telescope experiment data to the telemetry transmitter. The power supply for the instrumentation was provided by mercury batteries. 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「Vanguard 2」の詳細全文を読む スポンサード リンク
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