Geosynchronous satellite

At an altitude of 22,300 miles, geosynchronous satellites take exactly one day to orbit the earth, and therefore appear to hover over one spot above the equator. Receiving and transmitting antennae on the earth do not need to track such a satellite, are fixed in place and are much less expensive than tracking antennae. They have revolutionized global communications, positioning, navigation and television broadcasting. The original concept was developed by the science fiction author Arthur C. Clarke about 1945.