Communications satellite of a GEO satellite. Like LEOs, these satellites don’t maintain a stationary distance from the earth. This is in contrast to the geostationary orbit, where satellites are always approximately from the earth. Typically the orbit of a medium earth orbit satellite is about above earth. In various patterns, these satellites make the trip around earth in anywhere from 2 to 8 hours. In 1962, the first communications satellite, Telstar, was launched. It was a medium earth orbit satellite designed to help facilitate high-speed telephone signals. Although it was the first practical way to transmit signals over the horizon, its major
Satellite navigation slave signals allowed the receiver to deduce the distance to each of the slaves, providing a fix. The first satellite navigation system was Transit, a system deployed by the US military in the 1960s. Transit's operation was based on the Doppler effect: the satellites travelled on well-known paths and broadcast their signals on a well-known radio frequency. The received frequency will differ slightly from the broadcast frequency because of the movement of the satellite with respect to the receiver. By monitoring this frequency shift over a short time interval, the receiver can determine its location to one side or the