Impact of orbit determination methods on the characteristics of LEO satellites clock bias

On-board orbit determination and timing are the most convenient ways for low earth orbit (LEO) constellations to achieve spatiotemporal datum, but different calculation methods lead to different error coupling methods, and there is a lack of research on the impact of orbit determination methods on the characteristics of LEO clock bias. Therefore, this article is mainly based on the publicly measured data of 7 LEO satellites in orbit, including gravity recovery and climate experiment follow-on (GRACE-FO), sentinel-3, and swarm, combined with indicators such as accuracy, frequency stability and period term to comprehensively evaluate the impact of different orbit determination methods on the LEO clock bias characteristics. The results show that the clock bias calculated from reduced dynamic are smoother and less gross compared to kinematic, and the stability of clock bias obtained by reduced dynamic is higher based on better on-board clocks and observations. However, two orbit determination methods have no significant impact on the accuracy and periodic term of clock bias. Meanwhile, under the same orbit determination method, the GRACE-FO clock has the highest accuracy, better than 1ns, reach E-13 level for 100s and E-14 for 1000s stability, slightly better than BeiDou-2 rubidium clock, equivalent to Beidou-3 rubidium clock and inferior to BeiDou-3 Passive Hydrogen Maser clock. Next is sentinel-3, the worst is swarm, and the clock bias of sentinel-3 and swarm have obvious periodic characteristics.