An Approach to Resolve Integer Ambiguity of GPS Carrier Phase Difference for Spacecraft Attitude Determination

This paper presents a new approach to resolve integer ambiguity and achieve instantaneous spacecraft attitude from phase information of global positioning system signals, without requiring independent attitude information from traditional attitude sensors. A newly approached algorithm based on Gram-Schmidt orthonormalisation is proposed for medium length baseline observations. Using an attitude algorithm from vector observations, an instantaneous estimated attitude is obtained from only four phase measurements collected from only two baseline observations. The implemented algorithms are tested with a flight data collected onboard a mini-satellite orbiting in low Earth orbit. The results showed that a coarse attitude solution is achieved from phase information of stand-alone global positioning system signals.