GPS Phase-Connected, Precise Point Positioning of Low Earth Orbiters

A completely geometric approach for precise orbit determination (POD) of low earth orbiter (LEO) spacecraft has been devised by the authors which does not use dynamic models, but only data from the GPS receiver onboard the LEO and the International GPS Service (IGS) precise GPS ephemeris product. The strategy relies on combining the time-continuous measurement strength of the pseudorange and carrier-phase observables. The result is a straightforward, efficient procedure, which has the striking characteristics of providing a single receiver solution and is receiver platform-independent. This paper describes the mathematical model development of a kinematic, sequential least-squares filter/smoother implementing this form of GPS positioning. The strategy is then applied to orbit determination using data from the TOPEX/Poseidon, and CHAMP missions. The overall accuracy is assessed, with good quality data producing few-decimetre orbits in terms of total displacement error.