Communications satellite

Communications satellite, artificial earth-orbiting object used to relay radio signals between points on earth. The orbits of most such satellites are above the equator at a height of 22,300 mi (35,900 km). At that altitude a satellite orbits the earth at the same rate as the earth turns; it thus remains over a fixed point on the surface. The satellite carries a number of transponders that receive radio beams from the earth and retransmit them. The satellite is powered by solar cells. Communications satellites carry television programs, telephone calls, and business data.