The GPS-IIR replenishment satellites are produced by General Electric Astrospace (later Martin Marietta and Lockheed Missiles & Space) under a contract issued in 1989, which included 21 satellites based on the commercial AS-4000 bus. These provided improved navigation accuracy and longer autonomous satellite operation than earlier model GPS satellites. The satellites were three-axis stabilized and operated at downlink frequencies of 1572.42 MHz and 1227.6 MHz (L-Band) and 2227.5 MHz (S-Band). Lockheed was responsible for launch and flight operations support of the GPS-IIR through 2006.
Delta II is an American space launch system developed by McDonnell Douglas, now part of the Delta rocket family operated by United Launch Alliance. With more than 150 missions and a nearly perfect track record, Delta II has established itself as one of the most successful orbital launch systems.
