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geosynchronous orbit(jee-oh-sink -rŏ-nŭs) An Earth orbit made by an artificial satellite (moving west to east) that has a period of 24 hours, equal to the Earth's period of rotation on its axis. If the orbit is inclined to the equatorial plane the satellite will appear from Earth to trace out a figure-of-eight, once per day, between latitudes corresponding to the angle of orbital inclination to the equator. If the 24-hour orbit lies in the equatorial plane, and is circular, the satellite will appear from Earth to be almost stationary; the orbit and orbiting body are then termed geostationary. A geostationary orbit has an altitude of 36 000 km.
A geosynchronous or geostationary orbit is very difficult to achieve, requiring a very high orbital velocity. Satellites in such orbits are used for communications and navigation and also for certain types of Earth observations. Most communications satellites are now geostationary, with groups of three or more, spaced around the orbit, giving global coverage.