Mission typeNavigation
OperatorUS Air Force
COSPAR ID1990-008A
SATCAT no.20452
Mission duration7.5 years (planned)[1]
Spacecraft properties
Spacecraft typeGPS Block II[1]
Launch mass840 kilograms (1,850 lb)[2]
Start of mission
Launch date24 January 1990, 22:55:01 (1990-01-24UTC22:55:01Z) UTC
RocketDelta II 6925,[3] D191[3]
Launch siteCape Canaveral LC-17A[3]
End of mission
Deactivated18 August 2000 (2000-08-19)
Orbital parameters
Reference systemGeocentric
RegimeMedium Earth
Perigee altitude20,087 kilometres (12,481 mi)[4]
Apogee altitude20,275 kilometres (12,598 mi)[4]
Inclination54.6 degrees[4]
Period717.92 minutes[4]

USA-50, also known as GPS II-6 and GPS SVN-18, was an American navigation satellite which formed part of the Global Positioning System. It was the sixth of nine Block II GPS satellites to be launched, which were the first operational GPS satellites to fly.

USA-50 was launched at 22:55:01 UTC on 24 January 1990, atop a Delta II carrier rocket, flight number D191, flying in the 6925 configuration.[3] The launch took place from Launch Complex 17A at the Cape Canaveral Air Force Station,[5] and placed USA-50 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.[1]

On 25 February 1990, USA-50 was in an orbit with a perigee of 20,087 kilometres (12,481 mi), an apogee of 20,275 kilometres (12,598 mi), a period of 717.92 minutes, and 54.6 degrees of inclination to the equator.[4] The satellite had a mass of 840 kilograms (1,850 lb), and generated 710 watts of power.[2] It had a design life of 7.5 years,[1] and was retired from service on 18 August 2000.


  1. ^ a b c d e Krebs, Gunter. "GPS-2 (Navstar-2)". Gunter's Space Page. Retrieved 10 July 2012.
  2. ^ a b "Navstar 2-06". US National Space Science Data Center. Retrieved 10 July 2012.
  3. ^ a b c d McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 10 July 2012.
  4. ^ a b c d e McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 10 July 2012.
  5. ^ McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Page. Retrieved 10 July 2012.