Study On The Determination Of The Earth's Gravity Field From Satellite Gravimetry Mission GOCE

etermination of the earth's gravity field is always one of the main tasks of geodesy. The breakthrough of the satellite gravimetry technique as well as spatial technique and satellite positioning technique makes it possible to determine the fine structure of the earth's gravity field with unprecedented precision and resolution. The Satellite-to-Satellite Tracking (SST) and Satellite Gravity Gradiometry (SGG) are regarded as the most effective techniques for the determination of the earth's gravity field and its temporal variation. The SST technique represented mainly by CHAMP and GRACE satellite gravity missions has improved the accuracy of the earth's gravity field model by 1-2 order of magnitude in the part of long and mid wavelength. Aiming at an accuracy of lcm for the geoid at 100km resolution, the GOCE mission which combined SST-hl and SGG techniques was launched on 17 March 2009. This will bring greater breakthroughs for the investigation of the earth's gravity field.ith the successful launch of GOCE satellite, studies on data processing and applications of GOCE mission will become a hot issue in geosciences for the next several years. At the same time, the successful implementation of three international satellite gravity missions (CHAMP, GRACE and GOCE) takes opportunity as well as challenge for our study of geodesy and related fields. Speeding up the research in satellite gravimetry technique, and constructing our own autonomous gravity satellite system has become an inevitable trend. Therefore, researches on the theory and methodology of satellite gravimetry data processing have more realistic significance at present. Under the background of the scientific research, the theory and methods for the determination of the earth's gravity field based on GOCE satellite gravimetry technique are studied in this dissertation. And the corresponding GOCE data processing software package and analog simulation platform with autonomous copyright are developed. The ultimate purpose is not only to establish the foundation of the GOCE practical data processing and related application research, but also to accumulate experiences for the development of our country's gravity satellite system in the future. The main work and contributions in this dissertation are as following:fter the GOCE mission is comprehensively introduced, emphasis is focused on simulation study of LGOCE satellite gravimetry data, including satellite orbit data, gravity gradiometry data, gradiometer colored noise series, and so on. The effects of tidal perturbations on the motion of GOCE satellite and its performance of gradiometer measurement are estimated based on the simulation experiments. The results show that the tidal perturbations have greater effects on the observation of SST-hl, the maximum magnitude of each perturbation is larger than 1.0×10-9m/s2, whereas the tidal effects on the observation of SGG are relatively small, the magnitude of each perturbation is much less than GOCE gradiometer measurement accuracy of 3mE.he principle and practical numerical model of the acceleration approach for determining the earth's gravity field based on satellite orbit data are deeply studied. Because the noise in the orbit-derived satellite acceleration data is colored, whitening filters based on decorrelation technique are proposed to suppress the noise. Two whitening filters are constructed based on 3-points differential scheme and on ARMA model, respectively. As a test, simulated GOCE orbit data with different type of noises are used to recover the gravity field model. The results demonstrate that the gravity field models recovered from the decorrelation filtering methods have higher accuracy than those from equal weight method. Meanwhile, the effects of GOCE orbit error, accelerometer error and gross error on gravity field recovery are emulationally analyzed based on acceleration approach, and the performance of gravity field recovery using acceleration approach is also compared with energy balance approach, and then some useful conclusions are drawn.he adjustment models for simultaneously solving the calibration parameters of accelerometer and the potential coefficients based on point-wise accelerations or average accelerations are derived in detail, then a set of complete data processing scheme and process for recovering the earth's gravity field using acceleration approach is presented. Two earth's gravity field models up to degree and order 60 named WHUCHAMP-ACC60KP and WHUCHAMP-ACC60KA are respectively recovered by acceleration approach from 46 days of CHAMP kinematic orbits and accelerometer data. The results show that the above two models have the same accuracy, which is near to the accuracy of EIGEN-2, and better than EIGEN-1S. In addition, robust estimation is employed to suppress the influence of outliers remained in the preprocessed data, for gravity field recovery using acceleration approach. And a gravity field model up to degree and order 70 named WHUCHAMP-ACC70K is achieved by robust reweighting method based on IGG3 equivalent weight from 98 days of CHAMP data. The results show that WHUCHAMP-ACC70K has a higher accuracy than EIGEN-1S and EIGEN-2, which validate the effectiveness of robust estimation method.he principle and practical numerical model of the space-wise least-squares method for rigorously determining GOCE gravity field model are deeply studied. Analysis results show that the effect of GOCE orbit error on SGG is much less than the gradiometer measurement error, so the satellite orbit can be regard as known for GOCE gravity field recovery from gravity gradiomtery data. Two regularization algorithms, including FOT and Kaula, used in the GOCE gravity field determination are discussed. Numerical simulation shows that the two regularization methods can stabilize the solution and the difference of their treatment effects is very small. The ARMA recursive filtering method used to deal with GOCE gravity gradiometry colored noises is realized, and simulation results verify that this filtering method is practicability and effectiveness.ata processing scheme and process for the GOCE gravity field recovery based on spherical harmonic analysis approach are presented. The key problems such as data reduction, griding and polar gaps involved in spherical harmonic analysis approach are discussed and their solutions are also given. The wiener orbit filter (WOF) is designed and realized for preprocessing of the GOCE gravity gradiometry colored noises, and its effectiveness is verified by the numerical simulation results. It also provides an effective tool to preprocess of colored noises data for GOCE gravity field determination based on other space-wise methods, such as least-squares collocation method.ased on the principle of time-wise least square errors analysis, the calculation scheme and process for analog simulation analysis of the key technical indexes of SGG system are designed. Then the influences of various factors on the gravity field recovery from SGG data are analyzed. These influence factors include orbit height, orbital inclination, sampling interval, time span, gradiometer accuracy, measurement band-width, and combination of different gradient components. The simulation results can be as a reference for design and demonstration of the key technical indexes of SGG system. By simulation, the expected accuracy of GOCE mission is estimated. Using 6 months of SGG (Vxx,Vyy,Vzz,Vxz) data with 1 s sampling interval, the cumulative geoid height errors and cumulative gravity anomaly errors of the estimated gravity field model up to degree and order 200 are 21.57 cm and 0.412 mGal, respectively. When SGG and SST (with 5s sampling interval of disturbing potential) data are combined to estimate the gravity field, the corresponding cumulative errors are decreasing to 1.31 cm and 0.239 mGal, respectively. It proves that in order to achieve the aim of GOCE mission, SGG and SST data must be combined together for the gravity field recovery.he combined adjustment model for processing of SST and SGG data is derived, and two approaches for the determination of optimal weight are also investigated, including variance component estimate (VCE) and parametric covariance approach (PCA). On the basis of acceleration approach and space-wise least-squares method, the combined gravity field model up to degree and order 200 is recovered from 30 days of simulated GOCE orbits and SGG (Vxx,Vyy,Vzz) data with 5s sampling interval. The results show that the combined solution from combining SST and SGG data with equal weight is not optimal, and VCE method is better than PCA method for determining the optimal weight. However, the optimal weight determinated by VCE method also has some deviations from the theoretically optimal value that derived from the criterion of minimum RMS geoid error. For the SST and SGG optimal combined model, its accuracy of geoid heights and gravity anomalies between±83°latitude areas are 3.81cm and 1.056mGal respectively. Comparing to the combined solution solved from SST and component Vzz only, the accuracy of SST and SGG combined solution are improved about 1.0cm in geoid heights and 0.280mGal in gravity anomalies, respectively.atellite gravimetry boundary value problem solved from random boundary value conditions is investigated in detail. The solution of overdetermined random boundary value problem is derived, with spherical approximation boundary conditions of disturbing potential T and the radial gradient component Trr from the GOCE orbital plane. Furthermore, the solution of two boundaries (satellite orbital plane and earth's surface) overdetermined boundary value problem is also given, with terrestrial gravity anomaliesΔg as a constrained boundary condition. As a test, simulated disturbing potential T (SST) and radial gradient component Trr(SGG) on the GOCE orbital plane, and terrestrial gravity anomalies (Δg) data are combined to recover the gravity field model. The results show that the combined models are the optimal solution than those solved from only one type of observations. The combined solution from SST+SGG observations has an obvious improvement in the part of mid and low degrees, comparing with the solution from SGG observations only. And the accuracy of combined model from SST+SGG+Δg observations is better than the combined model from SST+SGG observations, especially in the part of high and mid degrees.he principle of least-squares spectral combination is studied, and then the general formulae of spectral weight and spectral combination for combining different type of observations are derived. On the basis of spherical harmonic analysis, the concrete forms of spectral weights corresponding to the disturbing potential T and radial gradient component Trr from the GOCE orbital plane are derived in detail. And the spectral combination formulae for processing of disturbing potential T and gradient component Trr are also given. We find that the solution of spectral combination is equivalent to the solution of satellite gravimetry boundary value problem, and their formulae have the same form and effectiveness. Furthermore, a spectral combination gravity field model up to degree and order 200 is constructed based on the principle of potential coefficients combination, using 30 days of simulated GOCE orbits and SGG (Vxx,Vyy,Vzz) data with 5s sampling interval. The above spectral combination model is combined from SST and SGG model, the SST model is solved by acceleration approach, and the SGG model is recovered from space-wise least-squares method. The results show that the accuracy of geoid heights and gravity anomalies between±83°latitude areas are 3.84cm and 1.058mGal respectively, which are similar to the accuracy of combined adjustment solution.