Thermospheric Mass Density Derived From LEO Satellites Precise Orbit Determination Data

For Low-Earth Orbit(LEO)satellites,atmospheric drag is the largest non-gravitational perturbation.This can affect missions like space mission and lifetime design,orbit and reentry prediction,and collision warning.In order to improve the application efficiency of satellite and the overall performance of LEO satellites system,it is important to improve the calculation accuracy of atmospheric drag.This thesis mainly focuses on LEO satellites orbit prediction and thermospheric mass density derived.The contributions are summarized as follows.1.In order to improve the orbit prediction accuracy of LEO satellites,the dynamic models are improved.We analyzed the affection of solar radiation pressure,different atmospheric density and drag calculation models on orbit prediction of LEO satellites.At the same time,the along-track empirical acceleration changes regularly with the argument of latitude in the fitting results of satellite precise orbit based on reduced-dynamic method.An empirical acceleration compensation model is established and applied to satellite orbit prediction.Real data tests reveal that the refined dynamic models can improve the accuracy of orbit prediction for LEO satellites.Among them,the empirical acceleration compensation method has obvious effect on the improvement of prediction accuracy,especially for the short-term prediction.Comared with the purely dynamic method,the empirical acceleration compensation method can improve the prediction accuracy by more than 80% within two hours,and the accuracy of one day can be improved by about 50%.In addition,the accuracy of the orbit prediction of different empirical atmospheric density models is different.In the actual orbit prediction,the selection of the appropriate atmospheric density model is helpful to obtain higher accuracy orbit prediction results.2.Deriving thermospheric mass density from LEO satellites precise orbit determination data.First,based on the partial derivative of orbital elements to time,we introduced the principle of deriving thermospheric mass density from precise orbit data.Subsequently,the deriving method is given.Taking CHEMP and GRACE-A satellites as examples,the differences of the results obtained by using different drag coefficient models in the density derived process are analyzed,as well as the differences between the retrieved results and those from accelerometer data,empirical atmospheric density models.The results show: The drag coefficient calculated by the Cook model and the Sentman model is diffient,and the latter model has greater fluctuation.The diffierence between the retrieved results is less than 10%.Compared with the retrieved results of accelerometer data,the density derived from CHAMP satellite precise orbit data deviate greatly.However,the deviation varies with altitude and local time,and the deviation on the dayside of the northern hemisphere and the southern hemisphere low latitude is significantly smaller than the deviation on the nightside.Compared with the results of empirical atmospheric models,the density derived from CHAMP satellite precise orbit data are in poor agreement with them,while the retrieved results from GRACE-A satellite precise orbit data show good agreement with them,and the relative deviation is less than 15%.