Onboard GPS Signal Augmentation for Spacecraft Formation Flying

Formation ying of multiple vehicles requires accurate information on the relative position and attitude between the vehicles. Carrier Phase Di erential GPS (CDGPS) can provide the necessary accuracy in position and attitude sensing to successfully carry out such missions. In missions with little to no visibility to the NAVSTAR constellation, CDGPS can still be used by augmenting the available signals with onboard transmitters broadcasting the L1 carrier signal modulated by a unique C/A code. The feasibility of this augmented GPS system is demonstrated with a two-vehicle formation in an indoor environment.