Determination of Earth rotation parameters by Beidou navigation satellite system

Earth Rotation Parameters (ERP) play an important role in astrometry, geophysics, and space geodesy. Beidou Navigation Satellite System (BDS) has three orbital types of satellites, i.e., Geostationary orbit (GEO), Inclined Geosynchronous Orbit (IGSO), and Medium Earth Orbit (MEO) satellites. The orbital diversity of BDS constellation provides the opportunity to study the influence of system-specific satellite constellation with different orbital characteristic on ERP. In this article, different strategies of ERP estimation are conducted in terms of different solar radiation pressure (SRP) models and different orbital types of satellites. For ERP derived from BDS MEO observations, compared with C04 products from International Earth Rotation and Reference System Service, the results show that the accuracy of ERP with extended Empirical CODE Orbit Model (ECOM) with 9 parameters (ECOM2) outperforms other SRP models (e.g., ECOM with 5 parameters (ECOM1) and ECOM1 with an empirical prior model (EMP + ECOM1)). In EMP + ECOM1 solutions, the application of a prior EMP model would intensify the influence of draconitic year in pole coordinates spectrum, while the visible signal of a period close to 7.4 days with ECOM1 solution can be mitigated. Moreover, the bias of B0 parameter in EMP + ECOM1 would cause a mean offset in Length Of Day (LOD). The accuracy of ERP is also affected by the BDS constellation characteristic. For pole coordinate, MEO-only solution with ECOM2 model shows the best accuracy, while the LOD achieves the best solution when 3 orbital types are employed. Additionally, using the combined constellation of MEO, IGSO, and GEO satellites can decorrelate some of the systematic signals, e.g., the spurious signals of LOD at 2.35-day and 3.5-day in MEO-only solutions are reduced. Likewise, the increase of orbital planes can reduce the amplitude of 3 cycles per draconitic year (close to 121 days) in the pole coordinate spectrum, which is the main error source in pole coordinates estimated from BDS MEO constellation. However, some signals around 10 ∼ 24, 33– and 50-day are found in the Y-pole coordinate and its rate.