Global Positioning System (GPS) was developed by the US Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55 degrees. These vehicles are placed in 6 orbit planes with four operational satellites in each plane.
GPS Block 2 was the operational system, following the demonstration system comprised of Block 1 (Navstar 1 - 11) spacecraft. These spacecraft were 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied 710 watts of power. They used S-band (SGLS) communications for control and telemetry and UHF cross-link between spacecraft. The payload consisted of two L-band navigation signals at 1575.42 MHz (L1) and 1227.60 MHz (L2). Each spacecraft carried 2 rubidium and 2 cesium clocks and nuclear detonation detection sensors. Built by Rockwell Space Systems for the US Air Force, the spacecraft measured 5.3 m across with solar panels deployed and had a design life of 7.5 years.
1 22231U 92079A 12338.00321768 -.00000040 00000-0 10000-3 0 4456 2 22231 056.1095 292.6539 0092577 255.3771 103.5935 02.00550456146761