Article: navigation satellite

navigation satellite artificial satellite designed expressly to aid the navigation of sea and air traffic. Early navigation satellites, from the Transit series launched in 1960 to the U.S. navy's Navigation Satellite System, relied on the Doppler shift. Based on the shift in the satellite's frequency, a ship at sea could accurately determine its longitude and latitude. The Global Positioning System (GPS), which uses a web of 24 Navstar satellites in 12-hour orbits, employs the more accurate triangulation method to determine position. Each satellite broadcasts time and position messages ...

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