On the potential contribution of BeiDou-3 to the realization of the terrestrial reference frame scale

Abstract

Since the release of the phase center calibrations for both the receivers and the satellites, the BeiDou Navigation Satellite System (BDS) became a new potential contributor to the realization of the terrestrial reference frame (TRF) scale of future International Terrestrial Reference Frame releases. This study focuses on the evaluation of the potential usage of the BDS-3 Medium Earth Orbit (MEO) constellation to the definition of the TRF scale. To that aim, we used ground calibrated BDS-3 satellite PCOs provided by the China Satellite Navigation Office and multi-GNSS robot calibrations for the ground antennas conducted by Geo++. Two ionosphere-free linear combinations of signals, namely B1I/B3I, and B1C/B2a, have been investigated to find out whether using different frequencies may lead to different TRF scale definitions. Differences between the z-components of the satellite phase offsets as given by manufacturer calibrations and those estimated based on IGS14 scale amount to 6.55 ± 12.56 cm and -0.32 ± 10.99 cm for B1I/B3I and B1C/B2a frequency pairs, respectively. On the one hand, the substantial deviation from the mean reflects the disparities in the quality of calibrations for the individual spacecraft, especially those manufactured by the Shanghai Engineering Center for Microsatellites (SECM). On the other hand, the difference between the two frequency pairs arises to a great extent from the doubtful quality of the SECM PCO calibrations, which certainly do not reflect the frequency dependence of the PCOs. Eventually, the mean scale bias with respect to IGS14 equals +0.546 ± 0.085 ppb, and +0.026 ± 0.085 ppb for B1I/B3I and B1C/B2a solutions, respectively, when using all 24 BDS-3 MEO satellites.