Abstract
The Chinese BeiDou Navigation Satellite System has provided a global-coverage service since 27 December 2018. Eighteen BD3 MEO satellites have been launched into space during 2017 and 2018. The signal constitution has been redesigned and four open service signals are used for transmission, including B1I, B1C, B2a and B3I. This paper focuses on the signal performance, Precise Orbit Determination (POD) and the atomic clock’s frequency stability issues of the BD3 satellites. The satellite-induced code bias issue found in BD2 satellites multipath combination has been proven to be eliminated in BD3 satellites. However, the pseudorange code of B1C is much noisier than that of other three frequencies, which may be related to the signal constitution and power distribution, as the minimum received power levels on the ground of B1C is 3 dB lower than that of the B2a signal. Similar results were achieved by the Ionosphere-Free combination residuals in POD using four signals, B1I-B3I, B1I-B2a, B1C-B3I and B1C-B2a, and the phase residual of B1C-B2a combination performed best. Considering the noise amplitude and compatibility with other GNSS (Global Navigation Satellite System), the B1C-B2a combination is recommended in priority for precise GNSS data processing. GFIFP combinations were also implemented to evaluate the inter-frequency phase bias of the four signals. The experimental results showed that the systematic signal with an amplitude of about 2 cm could be found in the GFIFP series. In addition, multi-GNSS POD was performed and analyzed as well, using about a hundred global-distributed IGS and iGMAS stations. Furthermore, the atomic clock’s frequency stability was estimated using the parameters of clock bias calculated in POD and the Overlap Allan Deviations showed that the frequency stability of BD3 reached approximately 2.43 × 10−14 at intervals of 10,000 s and 2.51 × 10−15 at intervals of 86,400 s, which was better than that of the GPS BLOCK IIF satellites but worse than that of Galileo satellites.
Highlights
With the implementation of the three-stage development plan of the BeiDou Navigation Satellite System (BDS), China started to provide local and global service at the end year of 2012 and 2018, respectively
Three types of constellations were employed by BDS, including GeoSynchronous Orbit (GEO), Inclined GeoSynchronous Orbit (IGSO) and Medium Earth Orbit (MEO)
The BD2 satellite bus is equipped with four rubidium atomic clocks, in which two are from the Spectra Time company and the others are manufactured in China, but the improved rubidium atomic frequency standard (RAFS) and the Passive Hydrogen Maser (PHM) made in China are equipped in the BD3 satellites
Summary
With the implementation of the three-stage development plan of the BeiDou Navigation Satellite System (BDS), China started to provide local and global service at the end year of 2012 and 2018, respectively. New navigation signal constitution and inter-satellites links measurements are employed in the BD3 GEO and MEO satellites, which is helpful for weak signal tracking, autonomous orbit determination and expanding the short message service to global coverage. BD2 was the first navigation system in which all satellites provided signals of three frequencies, and many scholars were interested in the signal performance [5,6], multi-frequency Precise Positioning [7,8], precise orbit determination (POD) [9,10,11,12]. This paper focuses on the signal performance, Precise Orbit Determination (POD) and atomic clock’s frequency stability issues of BD3 FOC satellites, aiming at estimating BD3 performance as comprehensively as possible.
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