Research On Characteristics And Prediction Of BDS-3 Satellite Clock

At 9:43 on June 23,2020,the last GEO satellite of BDS-3 was successfully launched,and BDS-3 was fully deployed.This means that in the future,GNSS will provide multi-mode and multi frequency services,and BDS will become an important force in the GNSS service sharing system.BDS-3 space part contains 24 MEO satellites,3 IGSO satellites and 3 GEO satellites,among which IGSO and GEO satellites play an important role in satellite chain communication.The importance of satellite borne atomic clock as the time reference for the space part of navigation system is self-evident,while BDS-3 carries domestic high-precision rubidium clock and passive hydrogen clock.Considering the particularity of BDS-3 and the physical characteristics of the atomic clock,as well as the fact that BDS-3 has just been formally formed,it is necessary to make a comprehensive analysis of the performance of BDS-3 on-board clock.At the same time,considering the coupling between post-processing precision clock error and orbit period,the periodicity of clock error is analyzed,and on this basis,the clock error prediction model is studied.The main contents include:(1)This thesis summarizes and analyzes the performance evaluation indexes of satellite clock,introduces the preprocessing process of precise clock error,including the conversion of phase data and frequency data,and the elimination method of gross error,and introduces several commonly used stability calculation models and clock error prediction models.(2)Through the analysis of BDS-3 satellite except C61 is carried out by using long-term precision clock difference products.The second term model is used to fit the long-term precision clock difference data,and the phase,frequency,frequency drift and residual index are analyzed comprehensively.The concept of residual fluctuation amplitude caused by the difference of orbit inclination between IGSO and GEO hydrogen clock is proposed.(3)The Hadamard variance is used to calculate the stability of BDS-3 satellites except C61.The stability differences among different satellites are compared.The variation trend of stability of single satellite with time is analyzed.The reasons for the abnormal values of stability of individual satellites are analyzed.Paper calculates the frequency accuracy,and compares the frequency accuracy of each BDS-3 satellite clock.On the whole,the performance of BDS-3hydrogen clock is better than rubidium clock in terms of stability and frequency accuracy.(4)Using spectrum analysis analyses fitting residuals of clock error,this thesis compares stability differences between different satellites and the variation trend of the stability of a single satellite with time and the reasons for the abnormal value of the stability of a single satellite.(5)The results of spectrum analysis are used to build a spectrum analysis model,and the fitting residuals of polynomial model and spectrum analysis model are compared to verify the effectiveness of spectrum analysis model in reducing noise.The experimental results show that the spectral analysis model can effectively improve the prediction accuracy compared with the polynomial model.This paper proposes to replace the main period of the whole year data period analysis with the main period of the single month data period analysis result which has higher coupling degree with the forecast clock error,so as to construct a new period replacement spectrum analysis model and verify its feasibility.(6)This thesis used the correction of the starting point deviation to improve the spectral analysis prediction model,and verifies the improvement degree of the model.It summarizes and analyzes the necessity of introducing the correction of the deviation of the starting point in the clock error prediction,and summarizes the application of the correction.