关键词: 低轨卫星, 多普勒定位, 无迹卡尔曼滤波, SGP4

Abstract:

Due to its high signal power and rich frequency resources, orbit satellite navigation systems have shown huge positioning potential in the constrained environment of Global Navigation Satellite Systems. Positioning technology based on low-orbit satellites is becoming a research hotspot in the field of positioning. This paper aims at the problem of insufficient accuracy of the simplified general perturbations 4 （SGP4）, a closed-loop tracking algorithm based on improved unscented Kalman filter （UKF） is proposed in this paper. The proposed algorithm takes the satellite position and speed as the optimization goal, and makes full use of the pseudorange rate and pseudorange measurements obtained by the receiver from the signal to form a closed-loop model, which can dynamically adjust the estimation results and obtain better position and velocity estimates, and obtain better position and velocity estimates and integrate the SGP4 algorithm through confidence judgment to avoid errors in the UKF oscillation stage. Experiment based on 200 Monte Carlo simulation runs on 10 Starlink satellites shows that compared with the traditional SGP4 open-ring ephemeris orbital algorithm, the proposed method effectively reduces position and velocity errors, and achieves a 45.98% accuracy improvement in positioning applications. In the experiment, the average positioning error of the ephemeris of the receiver of the ephemeris is obtained by using an improved trackless Kalman filtering method to obtain the average positioning error of the ephemeris 88.16 m, which is 20.94% higher than that of the traditional UKF, which verifies the superiority of this method in the field of opportunity signal positioning of low-orbit satellites.

Key words: low-orbit satellite, Doppler positioning, unscented kalman filter （UKF）, simplified general perturbations 4 （SGP4）