Today, there are hundreds of satellites in orbit around Earth—many of them are communications satellites that transmit phone, audio, television, and other electromagnetic signals all around the globe. One of the best known communications satellite systems is the NAVSTAR Global Positioning System, or GPS. This is a system of twenty-four satellites orbiting Earth at an altitude of about 12,000 miles (19,300 kilometers) and speeds of 7,000 miles (11,260 kilometers) per hour. By obtaining simultaneous communications signals from several satellites at once, it is possible to pinpoint the location of a GPS receiver to a precision of just a few feet or meters anywhere on Earth. The GPS system is maintained by the U.S. government, at a cost of more than $1.3 billion per year. The economic and social benefit of this system, however, far exceeds this amount.