Earth-orbiting system capable of receiving a signal (e.g., data, voice, TV) and relaying it back to the ground.
Communications satellites have been a significant part of domestic and global communications since the 1970s. Typically they move in geosynchronous orbits about 22,300 mi (35,900 km) above the earth and operate at frequencies near 4 gigahertz (GHz) for downlinking and 6 GHz for uplinking.