USA-91
| Names | Navstar 2A-11 GPS IIA-11 GPS II-20 GPS SVN-37 |
|---|---|
| Mission type | Navigation |
| Operator | U.S. Air Force |
| COSPAR ID | 1993-032A[1] |
| SATCATno. | 22657 |
| Mission duration | 7.5 years (planned) 14.5 years (achieved) |
| Spacecraft properties | |
| Spacecraft | GPS IIA |
| Spacecraft type | GPS Block IIA[2] |
| Manufacturer | Rockwell International |
| Launch mass | 840 kg (1,850 lb) |
| Dimensions | 5.3 m (17 ft) of long |
| Power | 710 watts |
| Start of mission | |
| Launch date | 13 May 1993, 00:07:00UTC |
| Rocket | Delta II7925-9.5 (Delta D220) |
| Launch site | Cape Canaveral,LC-17A |
| Contractor | McDonnell Douglas |
| Entered service | 14 June 1993 |
| End of mission | |
| Disposal | Graveyard orbit |
| Deactivated | 18 March 2016 |
| Last contact | 20 December 2007 |
| Orbital parameters | |
| Reference system | Geocentric orbit[3] |
| Regime | Medium Earth orbit (Semi-synchronous) |
| Slot | C4 (slot 4 plane C) |
| Perigee altitude | 20,033 km (12,448 mi) |
| Apogee altitude | 20,334 km (12,635 mi) |
| Inclination | 54.9° |
| Period | 717.88 minutes |
USA-91,also known asGPS IIA-11,GPS II-20andGPS SVN-37,was an Americannavigation satellitewhich formed part of theGlobal Positioning System.It was the eleventh of nineteenBlock IIAGPS satellites to be launched.
Background
[edit]Global Positioning System (GPS) was developed by theU.S. Department of Defenseto provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its introduction, GPS has also developed into a valuable tool for a wide range of civilian uses and sectors, including surveying, tracking corporate vehicle fleets, and outdoor enjoyment (such as sailing, flying, and hiking). GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55.0°. These vehicles are placed in 6 orbit planes with four operational satellites in each plane.[1]
GPS Block 2 was the operational system, following the demonstration system composed of Block 1 (Navstar 1 - 11) spacecraft. These spacecraft were3-axis stabilized,nadirpointing usingreaction wheels.Dual solar arrays supplied 710 watts of power. They usedS-band(SGLS) communications for control and telemetry andUltra high frequency(UHF) cross-link between spacecraft. The payload consisted of twoL-bandnavigation signals at 1575.42MHz(L1) and 1227.60 MHz (L2). Each spacecraft carried 2rubidiumand 2Cesiumclocks and nuclear detonation detection sensors. Built byRockwell Space Systemsfor the U.S. Air force, the spacecraft measured 5.3 m across with solar panels deployed and had a design life of 7.5 years.[1]
Launch
[edit]USA-91 was launched at 00:07:00 UTC on 13 May 1993, atop aDelta IIlaunch vehicle,flight number D220, flying in the 7925–9.5 configuration.[4]The launch took place fromLaunch Complex 17A(LC-17A) at theCape Canaveral Air Force Station(CCAFS),[5]and placed USA-91 into a transfer orbit. The satellite raised itself intomedium Earth orbitusing aStar-37XFPapogee motor.[2]
Mission
[edit]On 14 June 1993, USA-91 was in an orbit with aperigeeof 20,033 km (12,448 mi), anapogeeof 20,334 km (12,635 mi), aperiodof 717.88 minutes, and 54.9° ofinclinationto theequator.[3]It broadcast signal PRN 07, and operated in slot 4 of plane C of the GPS constellation.[6]The satellite had a mass of 840 kg (1,850 lb). It had a design life of 7.5 years,[2]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 1000 km above the operational constellation on 18 March 2016.[7]
References
[edit]
- ^abc"Display: Navstar 2A-11 1993-032A".NASA. 14 May 2020.Retrieved19 December2020.
This article incorporates text from this source, which is in thepublic domain.
- ^abcKrebs, Gunter."GPS-2A (Navstar-2A)".Gunter's Space Page.Retrieved10 July2012.
- ^ab"Trajectory: Navstar 2A-11 1993-032A".NASA. 14 May 2020.Retrieved19 December2020.This article incorporates text from this source, which is in thepublic domain.
- ^McDowell, Jonathan."Launch Log".Jonathan's Space Report.Retrieved10 July2012.
- ^McDowell, Jonathan."Launch List".Launch Vehicle Database.Jonathan's Space Report. Archived fromthe originalon 15 August 2020.Retrieved10 July2012.
- ^Wade, Mark."Navstar".Encyclopedia Astronautica. Archived fromthe originalon 11 November 2002.Retrieved10 July2012.
- ^"50 SW to dispose of two GPS satellites".United States Air Force.Retrieved21 March2016.This article incorporates text from this source, which is in thepublic domain.