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Marisat satellites were the first maritime telecommunications satellites and were designed to provide dependable telecommunications for commercial shipping and the U.S Navy from stable geosynchronous orbital locations over the three major ocean regions. The three Marisat satellites, F1, F2, and F3, were built by Hughes Aircraft Corporation (HAC) for COMSAT Corporation starting in 1973. The satellites were designed to provide maritime telecommunications services in three large ocean areas, the Atlantic Ocean, the Pacific Ocean, and the Indian Ocean, and were located at 72.5° East longitude, 176.5° E, and 345° E in the geosynchronous orbital arc. The three-satellite Marisat system served as the initial INMARSAT constellation. Ownership of the three Marisat satellites was transferred to Lockheed Martin when it bought COMSAT Corp in 2000. The Marisat-F2 satellite was acquired by INTELSAT as part of the COMSAT General Corp. acquisition in October 2004. The three satellites were all launched in 1976.〔http://www.boeing.com/defense-space/space/bss/factsheets/376/marisat/marisat.html〕 MARISAT F1 was launched on 19 February 1976,〔http://www.astronautix.com/craft/marisat.htm〕 MARISAT F2 was launched on 10 June 1976, and Marisat F3 was launched at 22:44 GMT, 14 October 1976. Launch vehicle for the satellites was the McDonnell Douglas 2914 Delta rocket. The satellites were launched from Cape Canaveral by the National Aeronautics and Space Administration under contract with COMSAT. In 1981 the INMARSAT took over from the Marisat system. ==Design== The satellites were designed to be identical, with three communications payloads on board; an ultrahigh frequency UHF (240 to 400 MHz) payload for the U.S. Navy, L-band (1.5 to 1.6 GHz) for ship communications via voice, telex, facsimile and high speed data, and C-band (6/4 GHz) for communications to fixed shore stations. The Marisat satellites were a cylindrical spinning satellite design similar to earlier satellites like Syncom 1, Intelsat I and II, relying on the gyroscopic forces generated by rotating at approximately 30 rpm to provide stability in the Earth's gravitational field. They were originally designed to last 5 years, but survived much longer, with Marisat F2 operating successfully for 32 years. The cylindrical design of satellites is good for several reasons: #early satellites did not have high power computers and attitude control systems of more modern satellites, and the spinning design provides a good basic method for maintaining a known attitude in orbit about the earth, #the cylindrical design maximized the size of the satellite which could fit inside the nose cone (fairing) of the launch vehicle (rocket), and #the cylindrical design was a simpler design for a spacecraft which would have a rotating body with a de-spun payload module to allow the antenna to point continuously at the same target on the earth (see Nadir pointing). The Marisat satellites weighed about 1450 pounds (660 kilograms). Each satellite is 12 feet 6 inches (3.81 meters) in height and 7 feet 1 inch (2.15 meters) in diameter. 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「Marisat」の詳細全文を読む スポンサード リンク
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