Autonomous Orbit Determination for Two Spacecraft from Relative Position Measurements

A batch filter has been designed and analyzed to autonomously determine the orbits of 2 spacecraft based on measurements of the relative position vector from one spacecraft to the other. This system provides a means for high-precision autonomous orbit determination for systems that cannot be dependent on signals from the GPS constellation or ground stations. The filter uses a time series of the inertially-referenced relative position vector, and it uses orbital dynamics models for the two spacecraft. It estimates the 6element orbital state vectors of both spacecraft along with a drag parameter for each one. The observability of this system is demonstrated in this proof-of-concept study, and the filter's predicted position determination accuracy is analyzed for a number of situations. Position accuracies on the order of 1 m RMS are predicted for certain configurations.