A satellite stationed in geosynchronous orbit that acts as a microwave relay station, receiving signals sent from a ground-based station (earth station), amplifying them, and retransmitting them on a different frequency to another ground-based station. Initially used for telephone and television signals, communications satellites can also be used for high-speed transmission of computer data. Two factors affecting the use of satellites with computers, however, are propagation delay (the time lag caused by the distance traveled by the signal) and security concerns. See also downlink, uplink.
An artificial satellite that relays signals back to earth; orbits at the same rate the earth turns and so remains effectively stationary.
Relay station in space for sending telephone, television, telex, and other messages around the world. Messages are sent to and from the satellites via ground stations. Most communications satellites are in geostationary orbit, appearing to hang fixed over one point on the Earth's surface.
The first satellite to carry TV signals across the Atlantic Ocean was Telstar in July 1962. The world is now linked by a system of communications satellites called Intelsat. Other satellites are used by individual countries for internal communications, or for business or military use. A new generation of satellites, called direct broadcast satellites, are powerful enough to transmit direct to small domestic aerials. The power for such satellites is produced by solar cells (see solar energy). The total energy requirement of a satellite is small; a typical communications satellite needs about 2 kW of power, the same as an electric heater.