The Global Positioning System is a constellation of orbiting satellites that provides navigation data to military and civilian users all over the world. The system is operated and controlled by the 50th Space Wing, located at Schriever Air Force Base, Colo.
GPS satellites orbit the earth every 12 hours, emitting continuous navigation signals. With the proper equipment, users can receive these signals to calculate time, location and velocity. The signals are so accurate, time can be figured to within a millionth of a second, velocity within a fraction of a mile per hour and location to within 100 feet. Receivers have been developed for use in spacecraft, aircraft, ships and land vehicles, precision munitions, as well as for hand carrying.
GPS provides 24-hour navigation services including:
· Extremely accurate, three-dimensional location information (latitude, longitude and altitude), velocity (speed and direction) and precise time
· A worldwide common grid that is easily converted to any local grid
· Passive all-weather operations
· Continuous real-time information
· Support to an unlimited number of users and areas
· Support to civilian users at a slightly less accurate level than cryptographically keyed users
The GPS constellation is designed and operated as a 24-satellite system, consisting of six orbital planes, with a minimum of four satellites per plane.
The Evolved Expendable Launch vehicle is used to launch GPS satellites from Cape Canaveral Air Station, Fla., into nearly 11,000-mile circular orbits. While circling the earth, the systems transmit signals on two different L-band frequencies. Their design life is 10 years for Block IIR/M (but many are lasting longer), 12 years for Block IIF, and 15 years for Block III.