| Launches: | 1978 -1998 |
| Mission: | to provide the military with accurate height and position information |
| Status: | Mission Completed; satellites still in orbit |
| Organization: | DOD - USA |
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While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military. The GPS Operational Constellation consists of 24 satellites: 21 navigational SVs and 3 active spares orbit the earth in 12 hour orbits. These space vehicles (SVs) send radio signals from space. The orbits repeat the same ground track (as the earth turns beneath them) once each day. The orbit altitude is such that the satellites repeat the same track and configuration over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes ,with about four SVs in each, equally spaced 60 degrees apart, and inclined at about fifty-five degrees with respect to the equatorial plane. This constellation provides the user with between five and eight SVs visible from any point on the earth. The Master Control facility is located at Falcon Air Force Base in Colorado. These monitor stations measure signals from the SVs. GPS receivers convert SV signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time dissemination, and other research. Navigation in three dimensions is the primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals. Precise positioning is possible using GPS receivers at reference locations providing corrections and relative positioning data for remote receivers. Surveying, geodetic control, and plate tectonic studies are examples.
The information contained in this page was aided in production by GPS Overview
Monday, 30-Aug-1999 15:46:56 CDT
CSR/TSGC Team Web