OPS 5111

OPS 5111, also known as Navstar 1, NDS-1, GPS I-1 and GPS SVN-1, was an American navigation satellite launched in 1978 as part of the Global Positioning System development programme. It was the first GPS satellite to be launched, and one of eleven Block I demonstration satellites.

OPS 5111 was launched at 23:44 UTC on 22 February 1978, atop an Atlas E/F carrier rocket with an SGS-1 upper stage. The Atlas used had the serial number 64F, and was originally built as an Atlas F. The launch took place from Space Launch Complex 3E at Vandenberg Air Force Base, and placed OPS 5111 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-27 apogee motor.

By 11 April 1978, OPS 5111 was in an orbit with a perigee of 20075 km, an apogee of 20291 km, a period of 718 minutes, and 63.3 degrees of inclination to the equator. The satellite had a design life of 5 years and a mass of 758 kg. It broadcast the PRN 04 signal in the GPS demonstration constellation, and was retired from service on 17 July 1985.