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Little LEOs
Leo One USA


GLONASS (Russia)


   NAVSTAR GPS - Summary
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The Global Positioning System (GPS) satellite network is operated by the U.S. Air Force to provide highly accurate navigation information to military forces around the world. The network is also being used by a growing number of commercial products. 

The GPS space segment consists of into six orbital planes, requiring a minimum of four satellites in each, to operate. The GPS control segment consists of five monitoring stations (Hawaii, Kwajalein, Ascension Island, Diego Garcia, Colorado Springs), three ground antennas, (Ascension Island, Diego Garcia, Kwajalein), and a Master Control station located at Schriever AFB in Colorado. The NAVSTAR Global Positioning System is managed by the NAVSTAR GPS Joint Program Office at the Space and Missile Systems Center, Los Angeles Air Force Base, California.

Plane/Slot 1 2 3 4 5 (spare)


2A-21 (39) 2A-12 (25) 2A-28 (38) 2A-15 (27) 2-4 (19)
B 2A-18 (22) 2A-27 (30) 2-2 (13) 2A-22 (35) 2R-5 (44)
C 2A-24 (36) 2A-25 (33) 2A-19 (31) 2A-20 (37)  
D 2A-11 (24) 2R-3 (46) 2-5 (17) 2A-23 (34) 2-9 (15)
E 2R-4 (51) 2-8 (21) 2A-26 (40) 2R-7 (54) 2A-10 (23)
F 2R-6 (41) 2A-14 (26) 2R-2 (43) 2A-16 (32) 2A-17 (29)

Table 1: GPS Satellite Planes/Slots

Click on individual cells for more information on the satellite.

Note: Nomenclature used in this table: Block number (2, 2A or 2R), satellite within block. In parentheses, USAF space vehicle number of GPS satellite. Satellites GPS 2-1 (14), 2-3 (16), 2-6 (18), 2-7 (20) and 2A-13 (28) have been retired. GPS 2R-1 (42) was destroyed in a Delta launch failure in January 17, 1997.

The idea for a global positioning/navigation system was first proposed in 1940. There are four generations of the GPS satellite: the Block I, Block II/IIA, Block IIR and Block IIF. Block I satellites were used to test the principles of the system, and lessons learned from those 11 satellites were incorporated into later blocks. Block II and IIA satellites make up the current constellation. The third generation Block IIR satellites are currently being deployed as the Block II/IIA satellites reach their end-of-life and are retired. Block IIF satellites will be the fourth generation of satellites and will be used for operations and maintenance (O&M) replenishment.


Navigation Signal Timing and Ranging Global Positioning System


Number of Satellites 24 Active, 4 Spare
Geometry 6 planes, 4 satellites each
Orbit MEO - 20,200 km (10,900 nmi) circular, 55 inclination (Block I satellites orbited at 63 inclination)
Orbit Period 12 hours
Coverage Global
Initial Operational Capability (IOC)

1993 December 8

Full Operational Capability (FOC)

1995 April 27

Managed by: USAF NAVSTAR GPS Joint Program Office, Space and Missile Systems Center
Operated by:

USAF 50th Space Wing

Web Links: USAF GPS Web Site

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