GPS-2RM [Lockheed Martin] GPS-2R (Global Positioning System) or
Navstar-2RM (Navigation System using Timing And Ranging) are the
third evolution stage of the second generation of the GPS GPS
satellites 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. Block IIR satellites provided dramatic improvements over
previous blocks. They could determine their own position by
performing inter-satellite ranging with other IIR vehicles. They
also had reprogramable satellite processors ena