Comparison of shadow models and their impact on precise orbit determination of BeiDou satellites during eclipsing phases

Solar radiation pressure (SRP) is an extremely critical perturbative force that affects the GNSS satellites' precise orbit determination (POD). Its imperfect modelling is one of the main error sources of POD, whose magnitude is even to10(-9) m/s(2). The shadow factor (i.e., eclipse factor) is one crucial parameter of SRP, generally estimated by the cylindrical model, the conical model, or shadow models considering the Earth's oblateness and the atmospheric effect, such as the Perspective Projection Method atmosphere (PPMatm) model and Solar radiation pressure with Oblateness and Lower Atmospheric Absorption, Refraction, and Scattering Curve Fit (SOLAARS-CF) model. This paper applies the former four shadow models to determine the corresponding precise orbit using BeiDou satellites' ground-based observation, and then compared and assessed the orbit accuracy through Satellite Laser Ranging (SLR) validation and Inter-Satellite Link (ISL) check. The results show that the PPMatm model's accuracy is equivalent to the SOLAARS-CF model. Compared with the conical shadow model, SLR validations show the orbit accuracy from the PPMatm and SOLAARS-CF model can be generally improved by 2-10 mm; ISL range check shows that the Root Mean Square (RMS) can be decreased by 2-7 mm. These results show that the shadow model in GNSS POD should fully consider the Earth's oblateness and the atmospheric effect, especially for the perturbative acceleration higher than 10(-10) m/s(2).