GPS satellite
From Wikipedia, the free encyclopedia
A GPS satellite is a satellite used by the NAVSTAR Global Positioning System (GPS). The first satellite in the system, Navstar 1, was launched 1978-02-22. The GPS satellite constellation is operated by the 50th Space Wing of the United States Air Force.
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[edit] Block I satellites
Beginning with Navstar 1 in 1978, ten "Block I" GPS satellites were successfully launched. One satellite, "Navstar 7", was lost due to an unsuccessful launch on 1981-12-18.[1] The Block I satellites were launched from Vandenberg Air Force Base using Atlas rockets that were converted intercontinental ballistic missiles. The satellites were built by Rockwell International at the same plant in Seal Beach, CA where the S-II second stages of the Saturn V rockets had been built.[2] The final Block I launch was conducted on 1985-10-09. The last Block I satellite was taken out of service on 1995-11-18.
[edit] Block II satellites
[edit] Initial Block II series
The first of the nine satellites in the initial Block II series was launched 1989-02-14; the last was launched 1990-10-01.[3] The final satellite of the series to be taken out of service was decommissioned 2007-03-15.
[edit] Block IIA series
Nineteen satellites in the Block IIA series were launched, the first on 1990-11-26 and the last on 1997-11-06. As of 2008-4-29, six satellites of this series have been removed from service.
Two of the satellites in this series, numbers 35 and 36, are equipped with laser retro-reflectors[4]. They can therefore be tracked independently of their radio signals, allowing unambiguous separation of clock and ephemeris errors.
[edit] Block IIR series
The Block IIR series are "replenishment" satellites developed by Lockheed Martin. Each satellite weighs 4,480 pounds (2,030 kg) at launch and 2,370 pounds (1,080 kg) once on orbit.[5] The first attempted launch of a Block IIR satellite failed on 1997-01-17 when the Delta II rocket exploded 12 seconds into flight. The first successful launch was on 1997-07-23. Twelve satellites in the series were successfully launched.
[edit] Block IIR-M series
The Block IIR-M satellites include a new military signal and a more robust civil signal, known as L2C.[6] Data is not yet being broadcast on L2C. There will be eight satellites in the Block IIR-M series, which are built by Lockheed Martin.[7] The first Block IIR-M satellite was launched on 2005-09-26. The most recent launch, GPS IIR-19 (M), was on 2008-03-15.
[edit] Block IIF series
On 2007-09-12 Boeing announced that it had completed assembly of the first satellite in the Block IIF series.[8] Boeing is under contract to build a total of twelve Block IIF satellites. The first is planned for launch in 2009 on a Delta IV rocket.[9]
[edit] References
- ^ BLOCK I SATELLITE INFORMATION. USNO.
- ^ Site: Boeing North American, Inc.. WTEC.
- ^ BLOCK II SATELLITE INFORMATION. USNO.
- ^ CDDIS Bulletin - June 1994, Volume 9 No. 5. NASA Goddard Space Flight Center.
- ^ Global Positioning System IIR. Lockheed Martin Space Systems Company.
- ^ GLOBAL POSITIONING SYSTEM. USAF.
- ^ Latest GPS IIR-M Sat Goes “Gold” For Lockheed Martin. SatNews.
- ^ Boeing Builds First GPS IIF Satellite. Boeing (2007-09-12).
- ^ Boeing Satellite Launch Schedule. Boeing (2008-01-15).
