Real-time carrier observation quality control algorithm for precision orbit determination of LEO satellites

Abstract

Low earth orbit satellites (LEOs) play an important role in communications, Earth observation and other applications. The real-time precise orbit determination (RTPOD) of LEOs plays an important role. However, the quality of carrier observations must be strictly controlled for the RTPOD of LEO satellites. Nevertheless, the ionospheric residual (IR) calculated from dual-frequency carrier observations at low sampling rates varies greatly due to the high speed of LEO satellites, and adopting the existing quality control method constrains the RTPOD performance in the highly dynamic environment. We present a new quality control for the receiver clock offset (QCCLK) algorithm, which combines LEO satellites' dynamic models with GNSS observations to detect carrier observation anomalies. Based on the QCCLK algorithm, real-time multi-GNSS automatic precise orbit determination (RTMG-APOD) software is designed. For comparison, we study the IR distribution at different sampling rates, revealing that the IR algorithm is not suitable for the quality control of LEO observations. RTMG-APOD software is used to analyze the RTPOD performance of the GFZ multi-GNSS final product (GBM), CNES real-time product (CNT) and IGS real-time service (RTS) product on GRACE Follow-On Level-1A observations. The RTPOD experiment results demonstrate that the 3D RMS of the GBM product is approximately 8 cm, and that of the CNT and RTS products is approximately 10 cm. Finally, an RTPOD experiment with one month of observations at different sampling rates using the GBM product and CNT real-time ephemeris verifies the stability of the QCCLK algorithm and its applicability to devices with low sampling rates.

Appendix

In Appendix Algorithm 1, the GNSS error corrections ${\varvec{d}}_{i}$ includes navigation satellite clock offset, phase hardware delays and antenna corrections of the receiver and satellite, Earth rotation corrections, relativistic corrections, etc. The $\sigma_{r}$ indicates the 3D LEO satellite positioning accuracy after RTPOD convergence, and the value of $\sigma_{r}$ is generally between 5 and 10 cm when using precise orbit and clock offset product. $\sigma_{t}$ indicates the maximum deviation of each navigation satellite from the median, which is usually 6–8 cm to detect 1 cycle or 0.5 cycle slip or gross errors. s represent the navigation satellite system,$d{\varvec{t}}_{r,i}^{s}$ is receiver clock offset vector, $\Delta t_{r,med}$ is the median of $\Delta {\varvec{t}}_{{{\varvec{r}},{\varvec{i}}}}^{s}$.