DOI: 10.5880/icgem.2018.002
title: A GOCE only gravity model GOSG01S based on the SGG and SST observations

description: We compile the GOCE-only satellite model GOSG01S complete to spherical harmonic degree of 220 using Satellite Gravity Gradiometry (SGG) data and the Satellite-to-Satellite Tracking (SST) observations along the GOCE orbit based on applying a least-squares analysis. The diagonal components (Vxx, Vyy, Vzz) of the gravitational gradient tensor are used to form the system of observation equations with the band-pass ARMA filter. The point-wise acceleration observations (ax, ay, az) along the orbit are used to form the system of observation equations up to the maximum spherical harmonic degree/order 130. The GOCE related satellite gravity models GOSG01S, GOTIM05S, GODIR05S, GOTIM04S, GODIR04S, GOSPW04S, JYY_GOCE02S, EIGEN-6C2 and EGM2008 are also validated by using GPS-leveling data in China and USA. According to the truncation at degree 200, the statistic results show that all GGMs have very similar differences at GPS-leveling points in USA, and all GOCE related gravity models have better performance than EGM2008 in China.
      This new model was developed by School of Geodesy and Geomatics (SGG) of Wuhan University (WHU) and Institute of Geodesy of University of Stuttgart. More details about the gravity field model GOSG01S is given in our paper “A GOCE only gravity model GOSG01S and the validation of GOCE related satellite gravity models ” (Xu X, Zhao Y, Reubelt T, et al. Geodesy and Geodynamics. 2017, 8(4): 260-272. http://dx.doi.org/10.1016/j.geog.2017.03.013). This work is supported by the National Key Basic Research Program of China (973 program, grant no.: 2013CB733301), the Major International (Regional) Joint Research Project (grant no.: 41210006).
description: GOSG01S is a static gravity field model complete to spherical harmonic degree of 220 derived by using the Satellite Gravity Gradiometry (SGG) data and the Satellite-to-Satellite Tracking (SST) observations along the GOCE orbit based on least-squares analysis.
      Input data:-- GOCE SGG data: EGG_NOM_2 (GGT: Vxx, Vyy, Vzz) in GRF (1/11/2009-31/5/2012)-- GOCE SST data: SST_PKI_2, SST_PCV_2, SST_PRD_2 (1/11/2009-5/7/2010)-- Attitude: EGG_NOM_2 (IAQ), SST_PRM_2 (PRM)-- Non-conservative force: Common mode ACC (GG_CCD_1i)-- Background model: tidal model (solid etc.), third-body acceleration, relativistic corrections, ...-- GOSG01S is a GOCE only satellite gravity model, since no priori gravity information was used in modelling procedure.
      Data progress strategies:
      Data preprocessing:- Gross outlier elimination and interpolation (only for the data gaps less than 40s).- Splitting data into subsections for gaps &gt; 40s
      The normal equation from SST data:- Point-wise acceleration approach (PAA)- Extended Differentiation Filter (low-pass)- Max degree: up to 130- Data: PKI, PCV, CCD
      The normal equation from SGG data:- Space-Wise LS method- Max degree: up to 220- Data: GGT, PRD, IAQ, PRM- Band-pass filter: used to deal with colored-noise of GGT observations (pass band 0.005-0.041Hz )- Forming the normal equations according to subsections- Spherical harmonic base function transformation instead of transforming GGT from GRF to LNRF 
     Combination of SGG and SST:- Max degree: up to 220- The VCE technique is used to estimate the relative weights for Vxx, Vyy, Vzz- Tikhonov Regularization Technique (TRT) is only applied to near (zonal) terms (m&lt;20)- Strictly inverse the normal matrix based on MPI