One is the Global Positioning System, abbreviated as GPS. It consists of three major components: space satellites, ground monitoring, and user reception. There are 24 satellites in space forming a distribution network, which are respectively distributed in six quasi Synchronous orbit with an inclination angle of 55 ° and a distance of 20000 km from the ground. There are four satellites in each orbit. GPS satellites orbit the Earth every 12 hours, enabling any location on the Earth to simultaneously receive signals from 7-9 satellites. There is a total of 1 main control station and 5 monitoring stations on the ground responsible for monitoring, telemetry, tracking, and control of satellites. They are responsible for observing each satellite and providing observation data to the main control station. After receiving the data, the main control station calculates the precise position of each satellite at each moment and transmits it to the satellite through three injection stations. The satellite then transmits this data to the ground through radio waves to the user's receiving device.

　　Note: This system was initially jointly developed by the United States Army, Navy, and Air Force in the 1970s. Its main purpose was to provide real-time, all-weather, and global navigation services for the three major fields of land, sea, and air. It was used for military purposes such as intelligence collection, nuclear explosion monitoring, and emergency communication, and was an important deployment of the United States' global dominance strategy. After more than 20 years of research and experiments, the GPS system cost 30 billion US dollars. It was not until March 1994 that 24 GPS Satellite constellation with a global coverage rate of 98% were officially deployed. Now the application of GPS system is not limited to the military field, but has developed into various fields such as vehicle navigation, atmospheric observation, geographical survey, ocean rescue, manned spacecraft protection and detection.

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