USA-84

USA-84
Names	Navstar 2A-06; GPS IIA-6; GPS II-15; GPS SVN-27
Mission type	Navigation
Operator	U.S. Air Force
COSPAR ID	1992-058A
SATCAT no.	22108
Mission duration	7.5 years (planned); 24.5 years (achieved)
Spacecraft properties
Spacecraft	GPS IIA
Spacecraft type	GPS Block IIA
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	9 September 1992,; 08:57:00 UTC
Rocket	Delta II 7925-9.5; (Delta D214)
Launch site	Cape Canaveral, LC-17A
Contractor	McDonnell Douglas
Entered service	11 October 1992
End of mission
Disposal	Graveyard orbit
Deactivated	18 April 2017
Orbital parameters
Reference system	Geocentric orbit
Regime	Medium Earth orbit; (Semi-synchronous)
Slot	A4 (slot 4 plane A)
Perigee altitude	19,914 km (12,374 mi)
Apogee altitude	20,335 km (12,636 mi)
Inclination	54.7°
Period	717.98 minutes
	Global Positioning System ← USA-83 (GPS IIA-5) USA-85 (GPS IIA-7) →

USA-84, also known as GPS IIA-6, GPS II-15 and GPS SVN-27, is an American navigation satellite which forms part of the Global Positioning System. It was the sixth of nineteen Block IIA GPS satellites to be launched.

Background

Global Positioning System (GPS) was developed by the U.S. Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. 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 were 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied 710 watts of power. They used S-band (SGLS) communications for control and telemetry and Ultra high frequency (UHF) cross-link between spacecraft. The payload consisted of two L-band navigation signals at 1575.42 MHz (L1) and 1227.60 MHz (L2). Each spacecraft carried 2 rubidium and 2 Cesium clocks and nuclear detonation detection sensors. Built by Rockwell Space Systems for 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

USA-84 was launched at 08:57:00 UTC on 9 September 1992, atop a Delta II launch vehicle, flight number D214, flying in the 7925–9.5 configuration.^[4] The launch took place from Launch Complex 17A (LC-17A) at the Cape Canaveral Air Force Station (CCAFS),^[5] and placed USA-84 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.^[2]

Mission

On 11 October 1992, USA-84 was in an orbit with a perigee of 19,914 km (12,374 mi), an apogee of 20,335 km (12,636 mi), a period of 717.98 minutes, and 54.7° of inclination to the equator.^[3] It had PRN 27, and operated in slot 4 of plane A of the GPS constellation.^[6] The satellite has a mass of 840 kg (1,850 lb). It had a design life of 7.5 years,^[2] but was in service for twenty years, until its retirement in October 2012. It was then kept on orbit spare until its disposal in 2017, where it was placed in a disposal orbit approximately 1000 km above the operational constellation.^[7]

References

^ ^a ^b ^c "Display: Navstar 2A-06 1992-058A". NASA. 14 May 2020. Retrieved 18 December 2020. This article incorporates text from this source, which is in the public domain.
^ ^a ^b ^c Krebs, Gunter. "GPS-2A (Navstar-2A)". Gunter's Space Page. Retrieved 10 July 2012.
^ ^a ^b "Trajectory: Navstar 2A-06 1992-058A". NASA. 14 May 2020. Retrieved 18 December 2020. This article incorporates text from this source, which is in the public domain.
^ McDowell, Jonathan. "Launch Log". Jonathan's Space Report. Retrieved 10 July 2012.
^ McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Report. Archived from the original on 15 August 2020. Retrieved 10 July 2012.
^ Wade, Mark. "Navstar". Encyclopedia Astronautica. Archived from the original on 11 November 2002. Retrieved 10 July 2012.
^ "U.S. Air Force says goodbye to 25-year-old GPS satellite". GPS World. 24 April 2017. Retrieved 7 May 2020.