Search

Abstract Since the first pair of BeiDou satellites was deployed in 2000, China has made continuous efforts to establish its own independent BeiDou Navigation Satellite System (BDS) to provide the regional radio determination satellite service as well as regional and global radio navigation satellite services, which rely on the high quality of orbit and clock products. This article summarizes the achievements in the precise orbit determination (POD) of BDS satellites in the past decade with the focus on observation and orbit dynamic models. First, the disclosed metadata of BDS satellites is presented and the contribution to BDS POD is addressed. The complete optical properties of the satellite bus as well as solar panels are derived based on the absorbed parameters as well the material properties. Secondly, the status and tracking capabilities of the L-band data from accessible ground networks are presented, while some low earth orbiter satellites with onboard BDS tracking capability are listed. The topological structure and measurement scheme of BDS Inter-Satellite-Link (ISL) data are described. After highlighting the progress on observation models as well as orbit perturbations for BDS, e.g., phase center corrections, satellite attitude, and solar radiation pressure, different POD strategies used for BDS are summarized. In addition, the urgent requirement for error modeling of the ISL data is emphasized based on the analysis of the observation noises, and the incompatible characteristics of orbit and clock derived with L-band and ISL data are illuminated and discussed. The further researches on the improvement of phase center calibration and orbit dynamic models, the refinement of ISL observation models, and the potential contribution of BDS to the estimation of geodetic parameters based on L-band or ISL data are identified. With this, it is promising that BDS can achieve better performance and provides vital contributions to the geodesy and navigation.

In this paper, the system error of inter-satellite-link measurements for autonomous navigation is studied, which is an important parameter for autonomous navigation technology based on inter-satellite-link of Beidou system. The physical meaning of system error of inter-satellite-link measurements and the influence of its error on autonomous navigation are clarified. On this basis, to solve the problem that it is difficult to calibrate the system error of inter-satellite-link measurements precisely on the ground before the satellite launches, a calibration method based on onboard measurement data for this parameter is put forward. Onboard test results show that the mean of the user range error of autonomous orbit determination is less than 6 m in 9 days using the system error of inter-satellite-link measurements calibrated according to the proposed method. Specially, the user range error is less than 3 m when the system error calibrated based on the latest measurement data is used. And in post-process, using the latest system error, the mean of user range error is less than 2.5 m and the error of autonomous time synchronization is within ±10 ns. All the results above prove the effectiveness of the calibration method for the system error of inter-satellite-link measurements and the effectiveness of the autonomous navigation algorithm. [ABSTRACT FROM AUTHOR]

The study "Geodesy and Time Reference in Space" (GETRIS), funded by European Space Agency (ESA), evaluates the potential and opportunities coming along with a global space-borne infrastructure for data transfer, clock synchronization and ranging. Gravity field recovery could be one of the first beneficiary applications of such an infrastructure. This paper analyzes and evaluates the two-way high-low satellite-to-satellite-tracking as a novel method and as a long-term perspective for the determination of the Earth's gravitational field, using it as a synergy of one-way high-low combined with low-low satellite-to-satellite-tracking, in order to generate adequate de-aliasing products. First planned as a constellation of geostationary satellites, it turned out, that an integration of European Union Global Navigation Satellite System (Galileo) satellites (equipped with inter-Galileo links) into a Geostationary Earth Orbit (GEO) constellation would extend the capability of such a mission constellation remarkably. We report about simulations of different Galileo and Low Earth Orbiter (LEO) satellite constellations, computed using time variable geophysical background models, to determine temporal changes in the Earth's gravitational field. Our work aims at an error analysis of this new satellite/instrument scenario by investigating the impact of different error sources. Compared to a low-low satellite-to-satellite-tracking mission, results show reduced temporal aliasing errors due to a more isotropic error behavior caused by an improved observation geometry, predominantly in near-radial direction within the inter-satellite-links, as well as the potential of an improved gravity recovery with higher spatial and temporal resolution. The major error contributors of temporal gravity retrieval are aliasing errors due to undersampling of high frequency signals (mainly atmosphere, ocean and ocean tides). In this context, we investigate adequate methods to reduce these errors. We vary the number of Galileo and LEO satellites and show reduced errors in the temporal gravity field solutions for this enhanced inter-satellite-links. Based on the GETRIS infrastructure, the multiplicity of satellites enables co-estimating short-period long-wavelength gravity field signals, indicating it as powerful method for non-tidal aliasing reduction. [ABSTRACT FROM AUTHOR]

Based on constellation designation,conditions of permanent inter-satellite-links were analyzed in order to solve problems of continual handoff caused by relative movements of satellites in different orbits in satellite networks.A scheme to design constellations with permanent inter-satellite-links was proposed,and conditions to maintain in-ter-satellite-links were analyzed.By simulations,results are shown and examples are introduced for verification.