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.
Background
It was part of the 21-satellite Global Positioning System (GPS) Block II series that provides precise position data (accurate to within 16 m) to military and civilian users worldwide. Its signals could be received on devices as small as a telephone. The GPS II satellites, built by Rockwell International for the Air Force Space Systems Division, each have a 7.5-year design life. The Air Force intends to launch a GPS II every 2 to 3 months until the constellation of 21 operational satellite and 3 spares is aloft. The GPS Block II join 7 operational Block 1 satellites.[2]
On 25 February 1990, USA-50 was in an orbit with a perigee of 20,087 km (12,481 mi), an apogee of 20,275 km (12,598 mi), a period of 717.92 minutes, and 54.6° of inclination to the equator.[4] The satellite had a mass of 840 kg (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.
^ abMcDowell, Jonathan. "Launch Log". Jonathan's Space Report. Retrieved 10 July 2012.
^ abMcDowell, Jonathan. "Satellite Catalog". 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.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).