The Defense Mapping Agency GPS Tracking network

Since the early 1960s, the Defense Mapping Agency (DMA) and its predecessors have been involved in satellite geodesy and the operation of satellite tracking networks to support satellite geodesy. In the mid-1980s, DMA developed and deployed a GPS tracking network. This tracking network consists of five stations deployed worldwide, which continuously collect and regularly communicate dual-frequency range and phase measurements and meteorological data to the DMA satellite ephemeris processing facility. On a weekly basis, these data, along with data from the GPS Operational Control Segment monitor stations, are processed to produce precise ephemerides that provide quality assurance for the GPS broadcast ephemerides and support the DMA precise point positioning program. This paper describes the development of DMA's GPS tracking network, and efforts currently under way to automate the stations and provide the capability to operate in an anti-spoofing environment.