NAVSTAR GPS
NAVigation Satellite Timing And Ranging
Global Positioning System
SPACE SEGMENT
There are four satellites in each of six orbital planes inclined at 55° to the equator.
The satellites are at altitudes of 10,898 nautical miles and have 11-hour,
56-minute orbital periods.
CONTROL SEGMENT
The control segment consists of five tracking stations that are located
throughout the world (Hawaii, Colorado, Ascension Island, Diego Garcia
Island, and Kwajalein Island).
The information obtained from tracking the
satellites is used in controlling and predicting their orbits. Three of the
stations (Ascension, Diego Gracia, and Kwajalein) are used for transmitting
information back to the satellites. The master control station is located at
Colorado Springs, Colorado. All data from the tracking stations are
transmitted to the master control station where they are processed and
analyzed. Ephemerides, clock corrections, and other message data are then
transmitted back to the three stations that are responsible for subsequent
transmittal back to the satellites.
USER’S SEGMENT
The user’s segment represents the ground-based receiver units that
process the satellite signals and arrive at a user’s position. This segment
consists of both military and civil activities for an unlimited number of
applications in a variety of air-, land-, and sea-based platforms.