Study On Acceleration Approach For Earth's Gravity Field Modelling Based On Satellite-to-Satellite Tracking Technique

The earth's gravity field is the basic physical field of the earth,representing the spatial distribution,movement and change of the earth's matter,and the earth gravity field recovery is one of the core scientific tasks of geodesy.With the rapid development of satellite gravimetry,the international satellite gravimetry missions(CHAMP,GRACE and GOCE)were successfully implemented at the beginning of this century,providing a large number of high-low,low-low satellite-to-satellite tracking and gravity gradient observations,which brought unprecedented opportunities and challenges for studying the fine structure of the earth's gravity field and modeling high-precision and high-resolution global gravity field.The recovery of high precision earth gravity field of medium to long wavelength based on satellite-to-satellite tracking observations has been extensively and deeply studied by scholars all over the world.Under this background,this paper studies the theory and method of earth gravity field recovery based on acceleration method from satellite tracking satellite technology.The main research contents and results of this paper are as follows:(1)The basic principle of satellite-to-satellite tracking measurement and the basic theory of global gravity field model inversion based on acceleration method are expounded,and the function model of earth gravity field inversion based on acceleration method with high-low and low-low satellite-to-satellite tracking observations is given.This paper studies and analyzes in detail the methods of determining the point acceleration of satellite along the orbit based on satellite orbit observation and GPS carrier phase observation,and proposes a new idea of earth gravity field recovery based on carrier phase differential acceleration,and presents the numerical solution method of gravity field model and the precision evaluation method.(2)The time-varying effects in the satellite gravity field model determined by the acceleration method are studied in depth.Based on the corresponding function models of various perturbation forces(solar and lunar gravitation,earth solid tides,sea tides,solid polar tides,ocean polar tides,relativistic effects,etc.),the effects of the perturbation forces on the satellite motion acceleration are analyzed and compared.The numerical analysis results of GOCE satellite show that the solar and lunar gravity has the largest influence,with the magnitude of about 10^-6m/s²,followed by the earth tide and the sea tide,which is about 10^-7m/s²,and the polar tide has the smallest,which is about 10^-9m/s².Considering the accuracy level of GOCE satellite's motion acceleration determined by GPS observation at present,the solar and lunar gravitation,earth tide,relativistic effect and other perturbation models need to be considered in the earth gravity field recovery.(3)The weighting method during satellite gravity field recovery based on position differential acceleration is studied in depth.Since the calculation of acceleration based on position differential leads to the amplification of high frequency error and introduces colored noise,the influence of different sampling intervals on the solution accuracy of gravity field model is analyzed in detail by using extended differential filter.The residual analysis method in acceleration domain based on the reference model is proposed.The residual acceleration autocorrelation sequence is directly used to construct the symmetric Toeplitz covariance matrix for rapid weighting,and the numerical analysis results show that this method can improve the precision of the gravity field solution as a whole.(4)Based on ESA,Graz and PKI orbits given in this paper,adopting the eight-order nine-point numerical differential algorithm,the 1s orbital acceleration of GOCE satellite of 71 days was determined from 30s sampling interval,and the orbital acceleration observation was determined by the publicly released GPS carrier phase observations of GOCE satellite.The accuracy of these kinds of acceleration observations in frequency domain and time domain was evaluated by using the acceleration of PRD orbital differential released by ESA as the true value.Results show that the precision of carrier phase method is better than that of position differential method,with accuracy of m Gal level in RTN direction.Compared with ESA orbital differentiation method,the precision of carrier phase method is improved by 12.75%,13.89%and 14.24%in tracking,cross-tracking and radial direction,respectively,while that of Graz orbital differentiation method is improved by 20.33%,5.10%and 5.55%in tracking,cross-tracking and radial direction,respectively.In addition,the accuracy in radial direction is the worst,with the error about 2 times of the tracking and cross-tracking direction.And the accuracy of polar region is worse than other regions.(5)Based on the acceleration determined by orbital differential and carrier phase differential,four 130-order satellite gravity field models are estimated by point acceleration method,and the precision of the solution models is analyzed with EIGEN-6C4 as the reference model.Results show that the cumulative geoid errors of the gravity field model based on the carrier phase differential method truncated to degree 70 and 130 are 5.57 and 36.11cm,respectively,and improved by 7.17%?21.16%?25.52%compared with ESA,Graz and SGG position differential method solution truncated to degree 130 degree respectively.The degree error RMS(delete m<5)curve of the inversion model indicates that the solution based on carrier phase differential is most accurate above 100 degree,and the solution of Graz orbital differential is most accurate less than 60 degree.(6)The feasibility of the gravity field recovery based on the point acceleration method from low-low satellite-to-satellite tracking is verified by the GRACE observation data simulated in 30 days.The results show that the solution model has a slightly higher precision of the zonal harmonic coefficients.(7)GRACE satellites tracking data from January to December 2008 are used to retrieve gravity field model up to d/o 100 based on the acceleration method.The results show that the solution are better than the AIUB-GRACE01S model in the whole frequency band.This is mainly because the background model has high precision when seperating the time-varying gravity signal;The calculation results are obviously better than EIGEN-GRACE01S model after d/o 80,and the accuracy of is slightly higher than that of EIGEN-GRACE02S model before d/o 20.(8)Software system was developed to recovery earth gravity field model based on the acceleration method from satellite-to-satellite tracking observations,including modules of datum transformation of time and space,perturbing force numerical analysis,the accurate determination of carrier motion acceleration,quick weighting,modeling and precision analysis of gravity field model,etc.The software system realizes the preprocessing of GRACE low-low satellite-to-satellite tracking and GOCE high-low satellite-to-satellite tracking in situ observations,and the inversion of earth gravity field model based on GRACE and GOCE data.