The research on system error of Inter-Satellite-Link (ISL) measurements for autonomous navigation of Beidou system

In this paper, the system error of inter-satellite-link measurements for autonomous navigation is studied, which is an important parameter for autonomous navigation technology based on inter-satellite-link of Beidou system. The physical meaning of system error of inter-satellite-link measurements and the influence of its error on autonomous navigation are clarified. On this basis, to solve the problem that it is difficult to calibrate the system error of inter-satellite-link measurements precisely on the ground before the satellite launches, a calibration method based on onboard measurement data for this parameter is put forward. Onboard test results show that the mean of the user range error of autonomous orbit determination is less than 6 m in 9 days using the system error of inter-satellite-link measurements calibrated according to the proposed method. Specially, the user range error is less than 3 m when the system error calibrated based on the latest measurement data is used. And in post-process, using the latest system error, the mean of user range error is less than 2.5 m and the error of autonomous time synchronization is within ±10 ns. All the results above prove the effectiveness of the calibration method for the system error of inter-satellite-link measurements and the effectiveness of the autonomous navigation algorithm.