Research On Simultaneous Solution For Precise Satellite Orbit And Earth Gravity Model From GRACE

As a basic physical field,the earth gravity field is the comprehensive reflection of mass distribution and movement in the interior of the earth.High accuracy and resolution Earth Gravity Model,as well as its time-varying signals,are very important information sources of earth science,including geodesy,geophysics and geodynamics,oceanography and so on,and have the important significance for scientific research.Simultaneous Solution Method?SSM?also called one-step method is an important solution to acquire earth gravity field,which is more theoretically rigorous,and has much higher accuracy of corresponding parameters than the traditional two-step method.This paper achieved the simultaneous calculation of GRACE satellite by situ data,including such parameters as precise satellite orbits,the earth gravity field model,the accelerometer calibration parameters and so on.To a certain extent,the accuracy of orbits were improved;Compared with several important international earth gravity field models,the accuracy of SSM model that was determined to degree and order 60 was pretty good;Then analyzed the effects of pulse thrusting on GRACE accelerometer calibration.This article also had a deep research on Space-borne GPS data preprocessing automatically and kinematic precise orbit determination by un-difference model.Compared with JPL orbits,it can achieve the same accuracy.The main work includes the following aspects:?1?Introduced the great significance of the high precision and resolution Earth Gravity Model for earth science,and summarized the research status for Space-borne GPS precise orbit determination and Earth Gravity Model determination.Emphatically introduced the present research status for "simultaneous" at home and abroad,including the progresses and advantages of this method,and pointed out the strategic points of work in this paper.?2?The fundamental mathematical models,basic principles and methods for"simultaneous" were introduced in detail for satellite precise orbit determination and earth gravity model determination.?3?The error correction models and data preprocessing method for space-borne GPS precise orbit determination were introduced.Then the kinematic precise orbits of GRACE satellites were determined by situ data on un-differenced model.Compared with the released orbits of JPL,the accuracy of determined kinematic orbits ofGRACE A satellite in the direction of the R,T,N was 3.01cm,2.76cm,2.43cm respectively,the GRACE B was 2.95cm,2.56cm,2.65cm respectively,which meant that the results had the same accuracy as JPL and indicated that the strategy of orbit determination and data preprocessing was very good.Compared with reduce-dynamic orbits that are determined at the same time,the accuracy of kinematic orbits of GRACE_A in the direction of the R,T,N was 2.4cm,1.9cm,1.7cm respectively,and the GRACE_B was 2.6cm,2.0cm,2.0cm respectively.The statistical result showed high accuracy,which illustrated that the kinematic orbits and reduced-dynamic orbits had a good consistency,and that the parameters configuration and strategy of precise orbit determination were reasonable.In addition,this paper analyzed the effects of different clock interval and GPS data sampling rate on the determination of kinematic orbits by three testing cases.The results showed that the effects were both just few mm,and the accuracy of 5CLK₁0S had an improvement of a fraction of a millimeters because of taking full use of SST data.?4?Achieved the simultaneous calculation of GRACE satellite by situ data including such parameters as precise orbits,the earth gravity field model,the accelerometer calibration parameters and so on.The SSM orbits had the same accuracy with JPL orbits,with small and smooth difference between them.While the orbit difference appeared a systematic bias of 1cm in the direction of R because of different force model configuration.Analyzing the effects of pulse thrusting on GRACE accelerometer calibration,results showed that it was necessary to get rid of pulse thrusting data to weaken the error of high frequency signal in the process of GRACE accelerometer calibration.Finally,compared with several important international earth gravity models,the SSM's?simultaneous solution to degree and order 60?cumulative geoid error was in the order of magnitude 10-3 m.