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Adaptive autonomous navigation method for MEO and HEO satellites based on weak constellation signal

An adaptive autonomous navigation method for medium earth orbit (MEO) and high earth orbit (HEO) satellites is proposed by using four constellation systems to overcome shortcomings of low visibility, liability and usability of single mode or dual-mode positioning systems. Firstly, based on the analysis of the visibility and compatibility of constellation satellites, satellites selection is realized by utilizing weighted geometric dilution of precision (WGDOP) algorithm. Secondly, considering the fact that there exists a non-synchronization phenomenon in the constellation systems, the synchronization error of each constellation system is estimated in real time as state variables of the navigation system. Thirdly, measurement noise variance matrix of the designed filter is adjusted adaptively in allusion to the problem of weakness of the received satellites signal and the strong uncertainty of the measurement noise of the satellite. Finally, simulation results are provided, which illustrate that compared with extended Kalman filter (EKF), the navigation accuracy can be enhanced by using the proposed adaptive filtering algorithm when there exists strong uncertainty in the measurement noise.