Research On Low Earth Orbit Spacecraft Orbit Prediction Strategy Based On Atmospheric Coefficient Modification

The spacecraft orbit prediction is the basis of the application research of spacecraft.It is of great significance in spacecraft measurement and control,rendezvous and docking,space debris collision calculation and orbital life estimation.At the same time,loworbiting spacecrafts have an important role in kinds of space tasks such as earth observation and earth science experiment.However,due to inaccurate perturbation of atmospheric resistance,the orbit prediction error of the low-orbit spacecraft is very large,especially in medium and long-term orbit prediction.In order to solve this problem,this paper studies the atmospheric parameter modification method of low-orbit spacecraft.Reduce the atmospheric perturbation error by modifying the atmospheric parameters and improve the accuracy of orbit prediction.Firstly,the definition of time system and coordinate system involved in orbit prediction is introduced,and the conversion method between different time system and coordinate system is introduced,too.Then,the orbital dynamics model is introduced in detail,and the concrete expression of each perturbation force in the orbital dynamics model is given,and the influence of each aerodynamic force on the low-orbit spacecraft is analyzed.Then,the mathematical expression form of SGP4 analytic orbit model is introduced.Two methods of modifying the resistance coefficient in SGP4 model are proposed by using the TLE data and GPS data of KZ-1 satellite.The two methods are carried out by simulation experiment.The results show that the two correction methods can improve the prediction accuracy of the SPG4 analytic orbit model by more than 20%.Secondly,study how to modify the atmospheric resistance coefficient in the shortterm forecast by using the KZ-1 satellite as the research object.By introducing the average atmospheric resistance coefficient during the orbit determination process,the average atmospheric resistance coefficient is used in the orbit prediction to improve the orbit prediction accuracy.The simulation results show that the maximum error of the position of the orbit prediction of KZ-1 in one day is within 2km.The applicability of the correction method to the spacecraft with different orbital height is verified by using the GPS data of CHAMP satellite.The simulation results show that the CHAMP satellite can forecast the maximum error of the position of the track within 150 m.Finally,the method of modifying the atmospheric resistance coefficient in medium and long term orbit prediction is studied.The atmospheric resistance coefficient is modified and compensated by three different time-varying function models by using the linear model,the polynomial model and the trigonometric function series model,which improves medium and long-term orbit prediction accuracy.The simulation results show that the three models can improve the medium and long-term orbit prediction accuracy of the KZ-1 satellite by more than 30%,and the polynomial model and the trigonometric function series model have more accurate results compared with the linear model.And the proposed long-term orbit prediction method is applied to the higher orbit height of the spacecraft by using CHAMP satellite's GPS data.The simulation results show that the three models all can improve the medium and long-term orbit prediction accuracy of CHAMP satellite by more than 20%.The polynomial model and trigonometric function series model have higher orbit prediction accuracy than linear model as the same as the KZ-1 satellite.So it is proved that the medium and long-term orbit prediction method is suitable for low-orbit spacecraft with different orbital height.