Analysis of Inner-consistency of BDS Broadcast Ephemeris Parameters and their Performance Improvement

Junping Chen, Qian Chen, Bin Wang, Sainan Yang, Yize Zhang, Jungang Wang

Peer Reviewed

Abstract:	The space segment of Beidou regional navigation satellite system (BDS) consists of 5GEO/5IGSO/4MEO satellites. Orbit information of the broadcast ephemeris is obtained by the Orbit Determination and Time Synchronization (ODTS) technique based on the observations of regional tracking network, while clock information is obtained by the satellite-station Two Way Time Transfer (TWTT) technique realizing the time synchronization among satellites and monitoring stations. ODTS and TWTT are two independent techniques. TWTT makes the difference of uplink and downlink range observations to estimate satellite clock offset with respect to the BDS system time, thus satellite clock estimation is less affected by the satellite orbits error. However, due to the reason that regional monitoring network are used for the ODTS process, satellite clock parameters estimated through the ODTS process are highly correlated with the orbit parameters and partly absorb the radial orbital parameters. In this paper, the estimated satellite clocks differences between the ODTS and TWTT techniques are analyzed in detail. It is shown that the differences can be divided into two parts: firstly, the systematic offset caused by the hardware bias of the equipment; secondly, periodical terms caused by the strong correlation of satellite clock and orbits in TWTT. On this basis, a refined strategy to improve the self-consistency of satellite clock and orbit in the BDS broadcast ephemeris is developed. Experimental results show that the SISRE of the refined broadcast ephemeris is reduced by more than 60%, and pseudo-range based single-point position accuracy using the refined BDS broadcast ephemeris is improved by 29%,32% and 19% in the North, East and Height components, respectively.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	300 - 306
Cite this article:	Chen, Junping, Chen, Qian, Wang, Bin, Yang, Sainan, Zhang, Yize, Wang, Jungang, "Analysis of Inner-consistency of BDS Broadcast Ephemeris Parameters and their Performance Improvement," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 300-306. https://doi.org/10.33012/2017.15092
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