Modeling, Analysis, and Simulation of GPS Carrier Phase for Spacecraft Relative Navigation

Models of Global Positioning System carrier-phase measurements have been derived, analyzed, and used to develop an offline simulator. This work is being carried out to support the development of carrier-phase differential Global Positioning System methods for relative navigation of formations of spacecraft that orbit in geosynchronous Earth orbit and high-altitude Earth orbit. Carrier-phase models are built up by considering signal generation on the Global Positioning System satellite and signal processing in the user receiver. An analysis oftneasured carrier-phase has been used to develop receiver design guidelines which guarantee that a receiver's outputs can be used by carrierphase differential Global Positioning System algorithms that resolve carrier-phase ambiguities as exact integers. The carrier-phase simulation includes errors such as incorrect Global Positioning System ephemerides, thermal noise, multipath, circular-polarization-induced phase windup, and altitude-dependent ionospheric delay. Simulation results demonstrate the efficacy and limitations of carrier-phase differential Global Positioning System methods for use in relative navigation of spacecraft formations.