Abstract
The basic system of the BeiDou global navigation satellite system (BDS-3) with 18 satellites has been deployed since December 2018. As the primary frequency standard, BDS-3 satellites include two clock types with the passive hydrogen maser (PHM) and the rubidium atomic frequency standard (RAFS). Based on the final precise orbit and clock product from Xi’an Research Institute of Surveying and Mapping (XRS), the atomic clock performance of BDS-3 satellites is evaluated, including the frequency accuracy, frequency drift rate, and frequency stability, and compared with GPS block IIF satellites with RAFS, Galileo satellites with PHM, and BDS-2 satellites. A data auto-editing procedure to preprocess clock data and assess the clock performance is developed, where the assessed results are derived at each continuous data arc and the outliers are excluded properly. The stability of XRS product noise is given by using some stations equipped with high-precision active hydrogen masers (AHM). The best stability is 8.93 × 10−15 and 1.85 × 10−15 for the averaging time of 10,000 s and 1 day, which is basically comparable to one-third of the in-orbit PHM frequency stability. The assessed results show the average frequency accuracy and drift rate of BDS-3 with RAFS are slightly worse while the stability is better than BDS-2 medium earth orbit (MEO) satellites. The 10,000 s stability is better but the 1-day stability is worse than GPS, which may be related to the performance of the BDS-3 RAFS clock. As for BDS-3 with PHM, the frequency accuracy is slightly worse than Galileo PHM satellites; the drift rate, when excluding C34 and C35, is basically comparable to Galileo and significantly better than GPS satellites; the stability is comparable to Galileo, where the 10,000 s stability is slightly worse than Galileo and better than GPS. The 1-day stability among BDS-3 PHM, GPS IIF RAFS, and Galileo PHM satellites is basically comparable.
Highlights
The BeiDou navigation satellite system (BDS) provides positioning, navigation, and timing (PNT) service with high continuity, reliability, and stability for global users
It can be seen that the frequency accuracy of BDS-3 passive hydrogen maser (PHM) is slightly better than BDS-3 rubidium atomic frequency standard (RAFS), while the frequency drift rate is significantly superior
The Hadamard derivation (HDEV) is basically comparable between BDS-3 RAFS and PHM satellites at the averaging time of 300 s, while the stability of 10,000 s and 86,400 s for BDS-3 PHM is better than BDS-3 RAFS, especially the 1 d stability
Summary
The BeiDou navigation satellite system (BDS) provides positioning, navigation, and timing (PNT) service with high continuity, reliability, and stability for global users. The high-precision and stable in-orbit atomic clock plays a key role in global satellite navigation system (GNSS) positioning and navigation. With increasing Beidou-3 satellites equipped with the passive hydrogen maser (PHM) and rubidium atomic frequency standard (RAFS) orbiting in space, the clock performance needs to be explored. The clock stability has a significant influence on PNT service. By the end of December 2018, there were 18 medium earth orbit (MEO) satellites and 1 geostationary earth orbit (GEO) satellite in orbit, which form the BDS-3 basic system and mainly serve counties in the.
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