Constrained GPS Precise Orbit Determination for Low Earth Orbiters

The degradations in accuracy of GPS precise orbit determination solutions for Low Earth Orbiters (LEOs) are analyzed under various constraints in this study. The constrained solutions are compared against a reference solution that is determined by post-processing dual-frequency data from the CHAllenging Mini-Satellite Payload (CHAMP). The constraints explored in this study are real-time processing requirements, availability of only single-frequency data, limited power onboard the LEO and limited CPU onboard the LEO. For the post-processing case, the longer the time that the receiver collects data, the more accurate the solution. This is not the case for real-time processing. In the case of post-processing, switching from single-frequency to dual-frequency data improves the orbit accuracy quite significantly in contrast to real-time processing. In the case of a limited CPU for real-time processing, altering the complexity of the dynamic models does not affect the accuracy with much significance.