Mission typeNavigation
OperatorUS Air Force
COSPAR ID1996-056A[1]
SATCAT no.24320[1]
Mission duration7.5 years (planned)[2]
Spacecraft properties
Spacecraft typeGPS Block IIA[2]
Launch mass1,816 kilograms (4,004 lb)[2]
Start of mission
Launch date12 September 1996, 08:49:00 (1996-09-12UTC08:49Z) UTC
RocketDelta II 7925-9.5, D238[3]
Launch siteCape Canaveral LC-17A[3]
Orbital parameters
Reference systemGeocentric
RegimeMedium Earth
Perigee altitude20,058 kilometres (12,463 mi)[4]
Apogee altitude20,305 kilometres (12,617 mi)[4]
Inclination54.7 degrees[4]
Period717.94 minutes[4]

USA-128, also known as GPS IIA-18, GPS II-27 and GPS SVN-30, is an American navigation satellite which forms part of the Global Positioning System. It was the eighteenth of nineteen Block IIA GPS satellites to be launched.

USA-128 was launched at 08:49:00 UTC on 12 September 1996, atop a Delta II carrier rocket, flight number D238, flying in the 7925-9.5 configuration.[3] The launch took place from Launch Complex 17A at the Cape Canaveral Air Force Station,[5] and placed USA-128 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.[2]

On 17 October 1996, USA-128 was in an orbit with a perigee of 20,058 kilometres (12,463 mi), an apogee of 20,305 kilometres (12,617 mi), a period of 717.94 minutes, and 54.7 degrees of inclination to the equator.[4] It broadcasts the PRN 30 signal, and operates in slot 2 of plane B of the GPS constellation.[6] The satellite has a mass of 1,816 kilograms (4,004 lb). It had a design life of 7.5 years,[2] and was decommissioned on July 20, 2011.[7]


  1. ^ a b "Navstar 2A-18". US National Space Science Data Center. Retrieved 10 July 2012.
  2. ^ a b c d e f Krebs, Gunter. "GPS-2A (Navstar-2A)". Gunter's Space Page. Retrieved 10 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.
  6. ^ Wade, Mark. "Navstar". Encyclopedia Astronautica. Retrieved 10 July 2012.
  7. ^ "NANU 2011-048". Celestrak. Retrieved 5 September 2012.