|Operator||US Air Force|
|Mission duration||7.5 years (planned)|
|Spacecraft type||GPS Block II|
|Launch mass||840 kilograms (1,850 lb)|
|Start of mission|
|Launch date||26 March 1990, 02:45:01UTC|
|Rocket||Delta II 6925, D193|
|Launch site||Cape Canaveral LC-17A|
|End of mission|
|Deactivated||13 December 1996|
|Perigee altitude||20,089 kilometres (12,483 mi)|
|Apogee altitude||20,268 kilometres (12,594 mi)|
USA-54, also known as GPS II-7 and GPS SVN-20, was an American navigation satellite which formed part of the Global Positioning System. It was the seventh of nine Block II GPS satellites to be launched, which were the first operational GPS satellites to fly.
USA-54 was launched at 02:45:01 UTC on 26 March 1990, atop a Delta II carrier rocket, flight number D193, flying in the 6925 configuration. The launch took place from Launch Complex 17A at the Cape Canaveral Air Force Station, and placed USA-54 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.
On 30 April 1990, USA-54 was in an orbit with a perigee of 20,089 kilometres (12,483 mi), an apogee of 20,268 kilometres (12,594 mi), a period of 717.84 minutes, and 55 degrees of inclination to the equator. The satellite had a mass of 840 kilograms (1,850 lb), and generated 710 watts of power. It had a design life of 7.5 years, however following problems with the satellite switching between timing standards, the satellite was declared unusable on 21 May 1996, and was decommissioned on 13 December.