Analysis of BDS-3 Onboard Clocks Based on GFZ Precise Clock Products

Abstract

The characteristics and performance of satellite clocks are important to the positioning, navigation, and timing (PNT) services of Global Navigation Satellite System (GNSS) users. Although China’s BeiDou-3 Navigation Satellite System (BDS-3) has been fully operational for more than one year, there is still a lack of comprehensive research on the onboard clocks of the entire BDS-3 constellation. In this study, the precise clock products of GeoForschungsZentrum (GFZ) from day-of-year (DOY) 1, 2021 to DOY 300, 2021 were used to analyze the characteristics and performance of BDS-3 onboard clocks from the following aspects: clock bias, frequency, drift rate, fitting residuals, periodicity, and frequency stability. Compared with BDS-2, the clock quality of BDS-3 satellites has been greatly improved, but there are still jumps in the clock offsets and frequency series of BDS-3 clocks. The drift rate of BDS-3 clocks varies within the range between −2×10−18 and 2×10−18 s/s2. The daily model fitting residuals of passive hydrogen masers (PHM) on BDS-3 medium Earth orbit (MEO), inclined geosynchronous orbit (IGSO), and geostationary (GEO) satellites are 0.15, 0.28, and 0.46 ns, respectively. The overlapping Allan deviation (OADEV) of BDS-3 MEO clocks is 4.0 × 10−14 s/s at a time interval of 1000 s. The PHMs on BDS-3 MEO satellites exhibit fewer periodic signals than those of Rb clocks. In addition, the precise clock offsets of the BDS-3 PHMs carried on the MEO, IGSO, and GEO satellites show different periodicities, which are similar to those of the corresponding types of BDS-2 satellites.

Real-Time Precise Point Positioning Method Considering Broadcast Ephemeris Discontinuities

“…It has been shown that BE-PPP with Galileo and the Global Positioning System (GPS) can provide a positioning accuracy of a few decimeters when post-processed products or real-time orbit and clock streams are not available (Carlin et al, 2021;Hadas et al, 2019). With the improved accuracy of the BDS-3 orbit and clock offset (Geng et al, 2022), BE-PPP for BDS has become feasible and offers better accuracy than standard point positioning (G. , but lower accuracy than traditional PPP (Hadas et al, 2019). Carlin et al (2021) conducted GPS/Galileo-integrated BE-PPP and estimated the signal-in-space range error (SISRE), which represents the projected orbit and clock errors introduced by the broadcast ephemeris, and obtained a significant improvement in positioning accuracy.…”

Analysis of BDS-3 Real-Time Satellite Clock Offset Estimated in Global and Asia-Pacific and the Corresponding PPP Performances

“…Kuang et al developed an uncombined model for the estimation of a BDS-3 multi-frequency real-time clock, and the STD of the double-differenced clock was generally less than 0.05 ns [17]. A series of research on the physical characteristics of atomic clocks show that the quality of BDS-3 atomic clocks is greatly improved compared with BDS-2, but the clock offset and frequency of BDS-3 still exist jumps, and the frequency drift varies in range from −2 × 10 −18 to 2 × 10 −18 s/s 2 [18]. About 70% of BDS-3 positioning solutions are within 0.7 m at 10 min thanks to the improvement in the BDS-3 atomic clock stability [19].…”

An Overview of a Special Issue on Upcoming Positioning, Navigation, and Timing: GPS, GLONASS, Galileo and BeiDou

“…Ref. [11] analyzed the precise clock products for BDS-3 from GeoForschungsZentrum and showed the characteristics and performance in terms of clock bias, frequency, drift rate, fitting residuals, periodicity, and frequency stability.…”