Term of the Day: GEO, MEO, and LEO

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GEO

Short for geosynchronous, or geostationary, earth orbit, a satellite system used in telecommunications. GEOs orbit the earth at 22,300 miles above the earth's surface. They are tied to the earth's rotation and are therefore in a fixed position in space in relation to the earth's surface. The satellite goes around once in its orbit for every rotation of the earth. The advantage of a GEO system is that the transmission station on earth needs to point to only one place in space in order to transmit the signal to the GEO satellite. GEO systems are used for transmissions of high-speed data, television signals and other wideband applications.

MEO

Short for medium, or middle, earth orbit, a satellite system used in telecommunications. MEO satellites orbit the earth between 1,000 and 22,300 miles above the earth's surface. MEOs are mainly used in geographical positioning systems and are not stationary in relation to the rotation of the earth.

LEO

Short for low earth orbit, a satellite system used in telecommunications. LEO satellites orbit the earth between 400 and 1,000 miles above the earth's surface. LEOs are mostly used for data communication such as e-mail, paging and videoconferencing. Because LEOs are not fixed in space in relation to the rotation of the earth, they move at very high speeds and therefore data being transmitted via LEOs must be handed off from one satellite to the next as the satellites move in and out of range of the earth-bound transmitting stations that are sending the signals into space. Because of the low orbit, the transmitting stations do not have to be as powerful as those that transmit to satellites orbiting at greater distances from the earth's surface. LEO telecommunication systems are a promising technology because they provide the ability for underdeveloped territories to acquire satellite telephone service in areas where it is either too costly or not geographically possible to lay land lines.