AN IMPROVED ALGORITHM FOR AUTONOMOUS ORBIT DETERMINATION OF NAVIGATION SATELLITE CONSTELLATION

Attention has recently been paid to the algorithm for determining the orbit of navigation satellites autonomously through inter-satellite observation. Through the analyses of the structure of the normal equation for the parameter estimation when using inter-satellite distance observations only, three singular values in the normal equation are found which are significantly smaller than the others. The normal equation is therefore ill-conditioned. If the appropriate measures are not used, this ill-conditioned situation would seriously affect the accuracy and stability of the orbit determination. Based on the discussion of the concrete causes of ill-conditioning, the fitting method by selection of the parameter weights is imported, and the algorithm of adding constraints based on the a priori information of some parameters of the satellites is proposed. The necessary number and type of parameters to be constrained are investigated in detail. How to set the regularization matrix and the regularization parameter are also discussed. Through comparison between the results of different schemes, an optimized scheme is proposed.