Solar Radiation Pressure Modeling For Beidou-3 Satellites

High-precision satellite orbit product is an important prerequisite to support BDS-3 highly precise services,and high-precision satellite orbits rely on accurate modeling of perturbation forces.Aiming at improving the orbit accuracy of BDS-3satellites,this paper analyzes the applicability of the current solar radiation pressure(SRP)model in BDS-3 satellite orbit determination,and improves it.The main work and conclusions of the paper are as follows:1)The applicability of the five-parameter ECOM model and the ECOM2 model in the precise orbit determination(POD)of BDS-3 satellites is analyzed.On this basis,the models are refined to obtain an empirical SRP model which is more suitable for BDS-3 satellites.The five-parameter ECOM model exhibits large orbit discontinuities when Sun elevation angle is small.It is proposed to introduce a first-order periodic term in the D direction to absorb the unmodeled SRP acceleration.The results show that the introduction of the first-order cosine period term can reduce the three-dimensional overlapping root mean square(RMS)values of BDS-3 satellites by about 11.4-37.4%.As for the ECOM2 model,strong correlations are observed between D_{2 c} and ₀D parameters as well as that between D_{2 s} and _sB parameters.Based on the strong correlations,the eight-parameter ECOM2 model and the seven-parameter ECOM2 model are proposed,where the parameters D_{2 c} and D_2c/D_2s are not estimated,respectively.The results show that the optimal overlapping orbit accuracy can be obtained by using the seven-parameter ECOM2 model,and the standard deviation of the CAST satellite SLR residuals can be reduced by 0.1-0.2 cm.Considering both the accuracy of overlapping orbit and SLR residuals,the seven-parameter ECOM2 model is more applicable for BDS-3 satellite POD when using the empirical SRP model.2)In addition to the empirical SRP model,the POD performance of the a prior box-wing model is further studied.The results show that the a prior box-wing model can reduce the three-dimensional overlapping RMS value by about 0.4 cm for CAST satellites launched before 2019,while has little effect on the overlapping accuracy of other satellites.In addition,compared with the empirical model,the a prior box-wing model can significantly reduce the correlation between the SLR residuals of SECM satellites and the Sun elongation angle,and reduce the standard deviation of the residuals by 1.4-1.5 cm.What's more,the influence of the antenna thrust on the POD of BDS-3 satellites is analyzed.The results show that antenna thrust can increase the mean values of SLR residuals by about 2.0 cm and 1.7 cm for CAST satellites and SECM satellites,respectively.Besides,the change of overlapping RMS values is less than 3 mm when cosidering antenna thrust.3)Based on the a prior box-wing model,the POD performance of BDS-3 satellite is analyzed when considering Earth albedo.On the basis of considering the antenna thrust,Earth albedo radiation pressure further increases the mean value of SLR residual of BDS-3 satellites by 1.3-1.7 cm.The effect of the Earth albedo radiation pressure on the SLR residual standard deviation and the overlapping accuracy does not exceed 2 mm.In addition,the differences between the empirical ERM-A model and the numerical grid ERM-CERES model are analyzed.The results show that the difference in the acceleration of the Earth albedo radiation calculated by the two models does not exceed 0.1 nm/s~2,and the difference of the overlapping accuracy and the SLR results is within 1 mm.4)On the basis of considering the earth albedo and antenna thrust,the adjustable box-wing model is used to reconstruct the rough optical parameter of BDS-3 satellites provided by the official with the actual observation data.And on this basis,the influence of the thermal radiation is considered.After using the reconstructed optical parameters,the overlapping orbit error of the BDS-3 satellites is significantly reduced,and the correlation between the SLR residuals and Sun elongation of the three BDS-3satellites except C20 is reduced.For CAST satellites,the mean SLR residuals are reduced by 1.8-3.4 cm and the standard deviation can be reduced by up to 0.4 cm.For SECM satellites,the reconstructed parameters have little effect on the SLR residual standard deviation,within 0.1 cm.On the basis of the adjustable box-wing model,thermal radiation acceleration caused by the-X surface is considering.The standard deviation of the SLR residual error of the C20 satellite has decreased by 0.1 cm.What's more,the correlation between the SLR residual and Sun elongation of the C20is reduced to a level comparable to that of other satellites.For SECM satellites,the SLR accuracy has no significant change.