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A geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit (GEO) is a circular orbit above the Earth's equator and following the direction of the Earth's rotation.〔( A geostationary Earth orbit satellite model using Easy Java Simulation Loo Kang Wee and Giam Hwee Goh 2013 Phys. Educ. 48 72 )〕 An object in such an orbit has an orbital period equal to the Earth's rotational period (one sidereal day), and thus appears motionless, at a fixed position in the sky, to ground observers. Communications satellites and weather satellites are often placed in geostationary orbits, so that the satellite antennas (located on earth) which communicate with them do not have to rotate to track them, but can be pointed permanently at the position in the sky where the satellites are located. Using this characteristic, ocean color satellites with visible and near-infrared light sensors (e.g. the Geostationary Ocean Color Imager (GOCI)) can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments. A geostationary orbit is a particular type of geosynchronous orbit, the distinction being that while an object in geosynchronous orbit returns to the same point in the sky at the same time each day, an object in geostationary orbit never leaves that position. The notion of a geosynchronous satellite for communication purposes was first published in 1928 (but not widely so) by Herman Potočnik. The first appearance of a geostationary orbit in popular literature was in the first Venus Equilateral story by George O. Smith,〔"(Korvus's message is sent) to a small, squat building at the outskirts of Northern Landing. It was hurled at the sky. … It … arrived at the relay station tired and worn, … when it reached a space station only five hundred miles above the city of North Landing." 〕 but Smith did not go into details. British science fiction author Arthur C. Clarke disseminated the idea widely, with more details on how it would work, in a 1945 paper entitled "Extra-Terrestrial Relays — Can Rocket Stations Give Worldwide Radio Coverage?", published in ''Wireless World'' magazine. Clarke acknowledged the connection in his introduction to ''The Complete Venus Equilateral''.〔"It is therefore quite possible that these stories influenced me subconsciously when … I worked out the principles of synchronous communications satellistes …", op. cit, p. x〕 The orbit, which Clarke first described as useful for broadcast and relay communications satellites, is sometimes called the Clarke Orbit.〔(【引用サイトリンク】 url = http://www2.jpl.nasa.gov/basics/bsf5-1.php )〕 Similarly, the Clarke Belt is the part of space about above sea level, in the plane of the Equator, where near-geostationary orbits may be implemented. The Clarke Orbit is about in circumference. == Practical uses == Most commercial communications satellites, broadcast satellites and SBAS satellites operate in geostationary orbits. A geostationary transfer orbit is used to move a satellite from low Earth orbit (LEO) into a geostationary orbit. The first satellite placed into a geostationary orbit was the Syncom-3, launched by a Delta D rocket in 1964. A worldwide network of operational geostationary meteorological satellites is used to provide visible and infrared images of Earth's surface and atmosphere. These satellite systems include: * the United States GOES * Meteosat, launched by the European Space Agency and operated by the European Weather Satellite Organization, EUMETSAT * the Japanese MTSAT * India's INSAT series A statite, a hypothetical satellite that uses a solar sail to modify its orbit, could theoretically hold itself in a geostationary "orbit" with different altitude and/or inclination from the "traditional" equatorial geostationary orbit. 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「Geostationary orbit」の詳細全文を読む スポンサード リンク
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