GPS receivers have been used successfully on low Earth orbit (LEO) satellite missions for several years. The use of a GPS receiver at altitudes higher than LEO, however, is non-trivial as the receiver will be outside the main lobe of the GPS broadcast signals, and it will have to track signals from GPS satellites transmitting from the other side of the Earth. This paper will review the special hardware and software adaptations required for GPS receiver operations on a medium Earth orbit or geostationary satellite, along with preliminary results from simulations and an in-orbit experiment.
