Comparison and Assessment on Long-Term Performance of BDS-2/BDS-3 Satellite Atomic Clocks

Abstract

Recently, the performance of the new-generation BeiDou Navigation Satellite System (BDS) satellite clocks has attracted considerable attention. There are two types of BDS clocks developed in China—namely, the new rubidium (Rb-II) and passive hydrogen maser (PHM)—and these can affect positioning, navigation and timing (PNT) services. In this paper, to comprehensively evaluate and analyze the performance of BDS satellite atomic clocks, the physical characteristics are exhibited, including phase, frequency, frequency drift and noise. The physical characteristics are applied to detect the switching of satellite clocks. The frequency stability of atomic clocks is assessed by overlapping Allan deviation (ADEV) and overlapping Hadamard deviation (HDEV). The periodic characteristics of satellite clock bias data are studied through spectrum analysis. Based on 550 day precision satellite clock bias data provided by Wuhan University, China, experiments were performed, focusing on the performance of the Rb-II and PHM clocks installed on BDS-3. Some valuable conclusions are obtained: (a) the BDS-3 satellite clocks perform better than BDS-2. The root mean square value of the frequency drift of BDS-3 satellite clocks is enhanced by 41% compared to BDS-2. The noise of BDS-3 is 0.216 ns, which is 55% better than BDS-2. (b) The frequency stability of BDS-2 satellite clocks is worse than that of BDS-3. The mean daily stability of BDS-2 and BDS-3 satellite clocks by ADEV is 5.29 × 10−14 and 5.36 × 10−14, respectively, while that with HDEV is 2.35 × 10−14 and 0.70 × 10−14. For PHM clocks, the stability at 10 000 s with ADEV and HDEV is 2.29 × 10−14 and 2.25 × 10−14, respectively, while the daily stability is 0.77 × 10 −14 and 0.67 × 10−14, respectively. (c) BDS geostationary orbit (GEO) and inclined GEO satellite atomic clocks have multiple significant periodic terms while the medium earth orbit satellite clocks only own one or two, which are related to the corresponding satellite orbital periods.

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

“…The OADEVs are 4.03×10 14 , 2.24×10 14 , and 0.22×10 14 1000 s, 10,000 s, and 1 day, respectively. • BDS-3 MEO Rb: It can be seen that the stability of MEO Rb clocks is slightly w than that of BDS-3 MEO PHMs, with the OADEVs being 4.3×10 2.56×10 14 , and 0.25×10 14 s/s at 1000 s, 10,000 s, and 1 day, respectively. The bottom two plots in Figure 10 depict the OADEVs for PHMs on IGSO and GEO satellites.…”

“…Moreover, the 2-hour, 10-hour, and 7-day prediction precisions of BDS-3 PHMs are about 0.3, 0.4, and 2.2 ns, respectively [16]. The daily stability of BDS-3 MEO satellites is about 2-5 × 10 −15 s/s [14]. The stability level of the BDS-3 PHMs is comparable to that of the PHMs of the Galileo as well as to the Rb clocks of the GPS Block IIF; meanwhile, the improved BDS-3 Rb clock is comparable to that of the Galileo Rb clock [17].…”

“…The BDS-3 constellation consists of three GEO, twenty-four MEO, and three IGSO satellites, which were developed and manufactured by CAST and the Shanghai Engineering Centre for Microsatellites (SECM) [9,10]. With construction of the BDS-3 system, some initial studies were carried out on the performance of the BDS-3e and BDS-3 MEO satellite onboard clocks [12][13][14][15][16][17]. The drift rate of Rb clocks on the BDS-3 MEO satellite is about 1.15 × 10 −18 s/s and that of the PHMs is 3.15 × 10 −19 s/s, which are 7.5% and 73% less than that of BDS-2 Rb clocks, respectively [14].…”

“…With construction of the BDS-3 system, some initial studies were carried out on the performance of the BDS-3e and BDS-3 MEO satellite onboard clocks [12][13][14][15][16][17]. The drift rate of Rb clocks on the BDS-3 MEO satellite is about 1.15 × 10 −18 s/s and that of the PHMs is 3.15 × 10 −19 s/s, which are 7.5% and 73% less than that of BDS-2 Rb clocks, respectively [14]. The noise level of BDS-3 MEO clocks evaluated by the daily fitting residuals is about 0.2 ns [15].…”

BeiDou-3 orbit and clock quality of the IGS Multi-GNSS Pilot Project

“…Orbit determination based on inter-satellite links (ISLs) was studied by several authors (Wang et al, 2019;Ruan et al, 2020;Guo et al, 2020;Xie et al, 2020) but none of the MGEX ACs uses ISL data due to lack of public availability. Chen et al (2021) found that the clock stability of the BDS-3 satellites is improved compared to BDS-2 but also shows periodicities at the orbital frequencies. Cao et al (2021) confirm the improved quality of the observed BDS-3 clocks although the Galileo clocks slightly outperform them.…”