Global Positioning System (GPS)
Originally designated the NAVSTAR (Navigation System with Timing And Ranging) Global Positioning System, GPS was developed by the US Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational uses (e.g. boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying.
GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55 degrees. These spacecraft are placed in 6 orbit planes with four operational satellites in each plane. All launches have been successful except for one launch failure in 1981. The full 24-satellite constellation was completed on March 9, 1994.
GPS receivers use triangulation of the GPS satellites' navigational signals to determine their location. The satellites provide two different signals that provide different accuracies. Coarse-acquisition (C/A) code is intended for civilian use, and is deliberately degraded. The accuracy using a typical civilian GPS receiver with C/A code is typically about 100 meters. The military's Precision (P) code is not corrupted, and provides positional accuracy to within approximately 20 meters. Numerous on-line tutorials on how GPS works and its applications are available, including those at the Univ. of Texas and Rentec International. GPS satellites are controlled at the GPS Master Control Station (MCS) located at Falcon Air Force Base outside Colorado Springs, Colorado. The ground segment also includes four active-tracking ground antennas and five passive-tracking monitor stations.
GPS Spacecraft
The first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system. The orbit inclination used for these satellites was 63 degrees, differing from the 55 degrees used for the operational system. The Block 2 spacecraft began the operational system. The Block 2A spacecraft (A = Advanced) were a slight improvement over the Block 2.
Related QuickLook Pages:
Launch Facts
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| Name | Int'l Desig. | Date | Site | Vehicle | Orbit | Mass(kg) |
| Notes | ||||||
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| GPS 1-1 (Navstar 1) | 1978-020A | 2/22/78 | WSMC | Atlas F | MEO | 450 |
| Also known as Navigational Development Satellite 1; 1st generation Global Positioning System | ||||||
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| GPS 1-2 (Navstar 2) | 1978-047A | 5/13/78 | WSMC | Atlas F | MEO | 453 |
| Also known as Navigational Development Satellite 2; 1st generation Global Positioning System | ||||||
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| GPS 1-3 (Navstar 3) | 1978-093A | 10/7/78 | WSMC | Atlas F | MEO | 450 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-4 (Navstar 4) | 1978-112A | 12/11/78 | WSMC | Atlas F | MEO | 450 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-5 (Navstar 5) | 1980-011A | 2/9/80 | WSMC | Atlas F | MEO | 433 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-6 (Navstar 6) | 1980-032A | 4/26/80 | WSMC | Atlas F | MEO | 450 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-7 (Navstar 7) | none | 12/18/81 | WSMC | Atlas E | FTO | 163 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-8 (Navstar 8) | 1983-072A | 7/14/83 | WSMC | Atlas E | MEO | 163 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-9 (Navstar 9) | 1984-059A | 6/13/84 | WSMC | Atlas E | MEO | 433 |
| 1st generation Global Positioning System | ||||||
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| GPS 1-10 (USA 5) | 1984-097A | 9/8/84 | WSMC | Atlas E | MEO | 770 |
| Also known as Navstar 10; 1st generation Global Positioning System | ||||||
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| GPS 1-11 (USA 10) | 1985-093A | 10/9/85 | WSMC | Atlas E | MEO | 163 |
| Also known as Navstar 11; 1st generation Global Positioning System | ||||||
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| GPS 2-1 (USA 35) | 1989-013A | 2/14/89 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-2 (USA 38) | 1989-044A | 6/10/89 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-3 (USA 42) | 1989-064A | 8/18/89 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-4 (USA 47) | 1989-085A | 10/21/89 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-5 (USA 49) | 1989-097A | 12/11/89 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-6 (USA 50) | 1990-008A | 1/24/90 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-7 (USA 54) | 1990-025A | 3/26/90 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-8 (USA 63) | 1990-068A | 8/2/90 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-9 (USA 64) | 1990-088A | 10/1/90 | ESMC | Delta 6925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-10 (USA 66) | 1990-103A | 11/26/90 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-11 (USA 71) | 1991-047A | 7/4/91 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-12 (USA 79) | 1992-009A | 2/23/92 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-13 (USA 80) | 1992-019A | 4/10/92 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-14 (USA 83) | 1992-039A | 7/7/92 | ESMC | Delta 7925 | MEO | 1165 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-15 (USA 84) | 1992-058A | 9/9/92 | ESMC | Delta 7925 | MEO | 1165 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-16 (USA 85) | 1992-079A | 11/22/92 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-17 (USA 87) | 1992-089A | 12/18/92 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-18 (USA 88) | 1993-007A | 2/3/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-19 (USA 90) | 1993-017A | 3/30/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-20 (USA 91) | 1993-032A | 5/13/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-21 (USA 92) | 1993-042A | 6/26/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-22 (USA 94) | 1993-054A | 8/30/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-23 (USA 96) | 1993-068A | 10/26/93 | ESMC | Delta 7925 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-24 (USA 100) | 1994-016A | 3/10/94 | ESMC | Delta 2 | MEO | 1665 |
| 2nd generation Global Positioning System; final element of initial GPS constellation | ||||||
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| GPS 2-25 (USA 117) | 1996-019A | 3/28/96 | ESMC | Delta 2 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-26 (USA 126) | 1996-041A | 7/16/96 | ESMC | Delta 2 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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| GPS 2-27 (USA 128) | 1996-056A | 9/12/96 | ESMC | Delta 2 | MEO | 1665 |
| 2nd generation Global Positioning System | ||||||
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