USA-91
| Mission type | Navigation |
|---|---|
| Operator | US Air Force |
| COSPAR ID | 1993-032A |
| SATCAT no. | 22657 |
| Mission duration | 7.5 years (planned) |
| Spacecraft properties | |
| Spacecraft type | GPS Block IIA |
| Manufacturer | Rockwell |
| Launch mass | 1,816 kilograms (4,004 lb) |
| Start of mission | |
| Launch date | 13 May 1993, 00:07:00 UTC |
| Rocket | Delta II 7925-9.5, D220 |
| Launch site | Cape Canaveral LC-17A |
| End of mission | |
| Disposal | Placed in a graveyard orbit |
| Deactivated | 18 March 2016 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime |
Medium Earth (Semi-synchronous) |
| Perigee | 20,033 kilometres (12,448 mi) |
| Apogee | 20,327 kilometres (12,631 mi) |
| Inclination | 54.9 degrees |
| Period | 717.88 minutes |
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.
Following decommissioning, it was kept as a reserve satellite. It was finally put in a disposal orbit approximately 1000km above the operational constellation on March 18, 2016.
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