The Determination Of Geocentric Motion And Its Time-varying Analysis With Multiple SLR Satellites

The geocenter motion reflects the global redistribution of mass and the interaction between solid earth and mass load.Annual variations induced by the redistribution of fluid mass in the Earth's surface layer are most prominentand can bias ice mass balance and sea level change estimates if neglected.Therefore,the study of geocentric motion can solve the problem that the ITRF implementation is not completely consistent with the definition of ITRS,thus improving the accuracy of reference frame origin.The main work of the dissertation is as follows:(1)We first summarize the research status of geocentric movement at home and abroad and the development of Satellite Laser Ranging technology,and we also elaborates the method of geocentric motion monitoring.The key issues are also discussed in terms of the reason of the geocenter motion,data collection principles,the theory of geocenter motins from SLR et al.(2)The results of geocentric motions obtained by dynamical inversion show that under the constraints of certain parameters,for the same decoding strategy,the low Earth orbiters(LEOs)LARES can effectively improve the performance of the traditional satellite laser ranging(LAGEOS-1/2,Etalon-1/2)in calculating the stability of the geocenter motion.The results show that the influence of different coefficient of drag coefficient on the calculation of the geocenter motion is very small.The gravity field orders to the fourth can get the highest accuracy of the geocenter motion in this study.(3)In this paper,MSSA method is applied to analyze the geocenter motion.Using this method,we found four main periodic components of geocentric time series in 15 years from 2002-2016.The results show that the significant annual cycles and the significant semi-annual cycles of the X?Y?Zdirection,and a consistent 5.3 year cycle is found in the Y and Z directions,which is different from the 3.5 year cycle in the X direction.lt can be said that the periodic characteristics of the geocentric motions on the long time scale are well restored,and the MSS A method also has some advantages in time series analysis with nonlinear changes.Then,the periodic sequences of the above geocentric motions are fitted by the least square fitting method.The amplitudes of the three directions of X,Y and Z are 2.6mm,2.1mm and 4.8mm,respectively,the results are consistent with those of other related researchers.