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Program: GPS


Global Positioning Satellite, also called Navstar (NAVigation System using Timing And Ranging); GPS IIA also known as NS-7C

American navigation satellite program operated by USAF. The satellites were placed by pairs on 20200 km circular orbits to provide localization (with 10 m precision). They were equipped with atomic clocks.

The program started with the launch between 1978 and 1985 of 10 satellites: block 1 (BI). Those enabled to check the concept and helped design the first operational generation. In 1987 28 block 2 (BII) satellites were ordered to Rockwell (9 BII and 19 BIIA, lifetime: 7 years). On 8 Dec 1993 the system was operational with 24 satellites available (4 satellites (slots) on 6 planes 60° apart). In 1989 Lockheed Martin (GE Astro Space) was ordered 21 satellites for the Block 2R (BIIR), for a total value of $800 million. The Block 2R satellites weigh about 2000 kg and have 10 years lifetime. They can operate during 180 days without groundstation intervention.

After the success encountered by the system in the civilian world, a new policy was taken in 1996 to stop degrading civil GPS signals within the next decade. This policy was applied in May 2000 with still certain areas remaining with degraded signal.

12 2R satellites (NS-7D) were launched from 2001 on with modifications. Those satellites have a second civilian frequency (1227.60 MHz) and 2 new military signals. The modification contract is worth $53 million, held by LMSS.

The GPS 2R-M incorporates 2 new military signals plus a more powerful signal.

The Block 2F (NS-7E) 12 satellites are to be provided by Boeing under a $1.3 billion contract. A third civilian frequency is planned at 1176.45 MHz. The will also feature critical, secure Operational M-codes for the U.S. military. Delayed to mid-2008.

In May 2008, the first 2 satellites (GPS 3A) were ordered from Lockheed Martin for $1.46 billion with option for 10 more. Those 2 are considered as R&D. First launch planned in 2015. The GPS 3A will provide significant enhancements: new L1C (civil) Galileo-compatible signal and increased Earth coverage Military-Code (M-Code) anti-jam power. Might loose the ability to degrate civilian signals.
The GPS 3B will enable a cross-linked command and control architecture, allowing these GPS III vehicles to be updated from a single ground station instead of waiting for each satellite to orbit in view of a ground antenna.
The GPS 3C will include a high-powered spot beam to deliver greater M-Code power for increased resistance to hostile jamming.

The GPS 3 Follow-On could comprise 22 satellites, and 3 times better accuracy, and remain operational for 15 years. Fully digital navigation payloads. Would carry laser retro-reflector arrays to enhance accuracy. The first 2 satellites were ordered from Lockheed Martin in 2018.


The Wide Area Augmentation System (WAAS) was officially setup in July 2003. At that time, 2 L1 signals are broadcast by Inmarsat 3F3 and Inmarsat 3F4. A ground network of 25 stations is also to be built.

Planes and slots


Plane Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6
A 2F-03 2R-M2 2F-05 2R-M6   2R-M6
B 2R-08 2F-01 2R-05 2R-M3 2F-09 2R-04
C 2R-M5 2F-04 2R-11 2R-M1 2F-10  
D 2R-13 2F-02 2R-09 2F-06 2R-03 2A-23
E 2F-08 2R-10 2R-M8 2R-07 2A-10 2F-11
F 2R-06 2R-M4 2F-07 2R-12   2R-02


Contact


Air Force Space Command


External resources


http://www.fas.org/spp/military/program/nav/gps.htm

http://www.navcen.uscg.gov/gps/geninfo/
http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html
http://www.lockheedmartin.com/gps



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