A Block IIR GPS satellite
Mission typeNavigation
OperatorUS Air Force
COSPAR ID2003-005A[1]
SATCAT no.27663[1]
Mission duration10 years (planned)[2]
Spacecraft properties
Spacecraft typeGPS Block IIR[2]
ManufacturerLockheed Martin[2]
Launch mass2,032 kilograms (4,480 lb)[2]
Start of mission
Launch date29 January 2003, 18:06:00 (2003-01-29UTC18:06Z) UTC
RocketDelta II 7925-9.5, D295[3]
Launch siteCape Canaveral SLC-17B[3]
Orbital parameters
Reference systemGeocentric
RegimeMedium Earth
Perigee altitude20,155 kilometres (12,524 mi)[4]
Apogee altitude20,344 kilometres (12,641 mi)[4]
Inclination55 degrees[4]
Period720.7 minutes[4]

USA-166, also known as GPS IIR-8 and GPS SVN-56, is an American navigation satellite which forms part of the Global Positioning System. It was the eighth Block IIR GPS satellite to be launched, out of thirteen in the original configuration, and twenty one overall. It was built by Lockheed Martin, using the AS-4000 satellite bus.[2]

USA-166 was launched at 18:06:00 UTC on 29 January 2003, atop a Delta II carrier rocket, flight number D295, flying in the 7925-9.5 configuration.[3] The XSS-10 satellite was carried as a secondary payload on the same rocket, but was deployed from the second stage of the three-stage rocket. The launch took place from Space Launch Complex 17B at the Cape Canaveral Air Force Station,[5] and placed USA-166 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37FM apogee motor.[2]

By 1 February 2003, USA-166 was in an orbit with a perigee of 20,155 kilometres (12,524 mi), an apogee of 20,344 kilometres (12,641 mi), a period of 720.7 minutes, and 55 degrees of inclination to the equator.[4] It is used to broadcast the PRN 16 signal, and operates in slot 1 of plane B of the GPS constellation. The satellite has a mass of 2,032 kilograms (4,480 lb), and a design life of 10 years.[2] As of 2012 it remains in service.


  1. ^ a b "Navstar 51". US National Space Science Data Center. Retrieved 11 July 2012.
  2. ^ a b c d e f g h Krebs, Gunter. "GPS-2R (Navstar-2R)". Gunter's Space Page. Retrieved 11 July 2012.
  3. ^ a b c McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 11 July 2012.
  4. ^ a b c d e McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 11 July 2012.
  5. ^ McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Page. Retrieved 11 July 2012.