March 31, 2008
The GPS constellations are now more than 30 years old. The first satellite, launched on Feb. 22, 1978, was in the Block I constellation. It was designated SVN 1/ PRN 4 and remained operational for 21.9 months. A total of 11 Block I satellites were launched from 1978 to 1985; one of the 11 failed to attain orbit. Since 1989, all satellites launched are designated as Block II.