A Block IIA GPS satellite
|Operator||US Air Force|
|Mission duration||7.5 years (planned)|
|Spacecraft type||GPS Block IIA|
|Launch mass||1,816 kilograms (4,004 lb)|
|Start of mission|
|Launch date||13 May 1993, 00:07:00UTC|
|Rocket||Delta II 7925-9.5, D220|
|Launch site||Cape Canaveral LC-17A|
|End of mission|
|Deactivated||20 December 2007|
|Perigee||20,033 kilometres (12,448 mi)|
|Apogee||20,327 kilometres (12,631 mi)|
USA-91, also known as GPS IIA-11, GPS II-20 and GPS SVN-37, was an American navigation satellite which formed part of the Global Positioning System. It was the eleventh of nineteen Block IIA GPS satellites to be launched.
USA-91 was launched at 00:07:00 UTC on 13 May 1993, atop a Delta II carrier rocket, flight number D220, flying in the 7925-9.5 configuration. The launch took place from Launch Complex 17A at the Cape Canaveral Air Force Station, and placed USA-91 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.
On 14 June 1993, USA-91 was in an orbit with a perigee of 20,033 kilometres (12,448 mi), an apogee of 20,327 kilometres (12,631 mi), a period of 717.88 minutes, and 54.9 degrees of inclination to the equator. It broadcast signal PRN 07, and operated in slot 4 of plane C of the GPS constellation. The satellite had a mass of 1,816 kilograms (4,004 lb). It had a design life of 7.5 years, and ceased operations on 20 December 2007.
- "Navstar 2A-11". US National Space Science Data Center. Retrieved 10 July 2012.
- Krebs, Gunter. "GPS-2A (Navstar-2A)". Gunter's Space Page. Retrieved 10 July 2012.
- McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 10 July 2012.
- McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 10 July 2012.
- McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Page. Retrieved 10 July 2012.
- Wade, Mark. "Navstar". Encyclopedia Astronautica. Retrieved 10 July 2012.
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