GPS satellite

A GPS satellite is a satellite used by the NAVSTAR Global Positioning System (GPS). The first satellite in the system, Navstar 1, was launched February 22, 1978. The GPS satellite constellation is operated by the 50th Space Wing of the United States Air Force.

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 December 18, 1981. [cite web | url = ftp://tycho.usno.navy.mil/pub/gps/gpsb1.txt | title = BLOCK I SATELLITE INFORMATION | publisher = USNO] 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.cite web | url = http://www.wtec.org/loyola/satcom2/e_02.htm | title = Site: Boeing North American, Inc. | publisher = WTEC] The final Block I launch was conducted on October 9, 1985. The last Block I satellite was taken out of service on November 18, 1995.

Block II satellites

Initial Block II series

The first of the nine satellites in the initial Block II series was launched February 14, 1989; the last was launched October 1, 1990. [cite web |url = ftp://tycho.usno.navy.mil/pub/gps/gpsb2.txt | title = BLOCK II SATELLITE INFORMATION | publisher = USNO] The final satellite of the series to be taken out of service was decommissioned March 15, 2007.

Block IIA series

Nineteen satellites in the Block IIA series were launched, the first on November 26, 1990 and the last on November 6, 1997. As of April 29, 2008, 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 [cite web|url=http://cddis.nasa.gov/bulletin_v9n5.html |title=CDDIS Bulletin - June 1994, Volume 9 No. 5 |publisher=NASA Goddard Space Flight Center] . They can therefore be tracked independently of their radio signals, allowing unambiguous separation of clock and ephemeris errors.

Block IIR series

The Block IIR series are "replenishment" satellites developed by Lockheed Martin. Each satellite weighs lb to kg | 4480 | precision=-1 at launch and lb to kg | 2370 | precision=-1 once on orbit. [cite web | url = http://www.lockheedmartin.com/products/GPS/ | title = Global Positioning System IIR | publisher = Lockheed Martin Space Systems Company] The first attempted launch of a Block IIR satellite failed on January 17, 1997 when the Delta II rocket exploded 12 seconds into flight. The first successful launch was on July 23, 1997. Twelve satellites in the series were successfully launched.

Block IIR-M series

The Block IIR-M satellites include a new military signal and a more robust civil signal, known as L2C. [cite web | url = http://www.losangeles.af.mil/library/factsheets/factsheet.asp?id=5325 | title = GLOBAL POSITIONING SYSTEM | publisher = USAF] 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. [cite web | url = http://www.satnews.com/cgi-bin/display_story.cgi?number=2008555989 | title = Latest GPS IIR-M Sat Goes “Gold” For Lockheed Martin | publisher = SatNews] The first Block IIR-M satellite was launched on September 26, 2005. The most recent launch, GPS IIR-19 (M), was on March 15, 2008.

Block IIF series

On September 9, 2007 Boeing announced that it had completed assembly of the first satellite in the Block IIF series. [cite web | url = http://www.boeing.com/news/releases/2007/q3/070912b_nr.html | title = Boeing Builds First GPS IIF Satellite | date = September 12, 2007 |publisher = Boeing] 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.cite web | url = http://www.boeing.com/defense-space/space/bss/launch/launch_sched.html | title = Boeing Satellite Launch Schedule | publisher = Boeing | date = January 15, 2008]

References

See also

*List of GPS satellite launches