GOCE Gravity Field Model

Space-Wise Solution - Second generation

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Model Characteristics
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GOCE input data:
- The full list of input data to the space-wise model is provided in the IHD file.
- Basically the solution makes use of both satellite tracking data derived from the 
  on-board GPS receiver and gravity gradients observed by the on-board electrostatic 
  gradiometer.
- In particular kinematic orbits with their error estimates are used for SST gravity 
  field recovery, while reduced dynamic orbits are used for geo-locating gravity 
  gradients. The information coming from the electrostatic gradiometer are gravity 
  gradients, common mode accelerations and satellite attitude quaternions.
- Data period: 20091031T000000:20100705T235959

A-priori information used:
- No corrections to any prior gravity field model are computed (GOCE-only model).
- EIGEN5C was used for signal covariance modelling.
- FES2004 was used for ocean tide modelling.

Processing procedure:
- The space-wise approach is a multi-step collocation procedure, developed in the 
  framework of the GOCE HPF data processing for the estimation of the spherical harmonic 
  coefficients of the Earth gravitational field and their error covariance matrix.
- The SST model is derived by first estimating the along track gravitational potential by 
  applying the energy conservation approach to kinematic orbits. Then a spherical grid of 
  potential values is computed at mean satellite altitude by local collocation and the 
  spherical harmonic coefficients are derived by numerical integration from the grid 
  values.
- The SST+SGG model is computed by applying an iterative scheme which basically consists 
  of a Wiener orbital filter to reduce the strongly time correlated noise of the 
  gradiometer, a spherical interpolation at mean satellite altitude by jointly applying a 
  local collocation to the filtered potential (T) and gravity gradients (Txx, Tyy, Tzz, 
  Txz) and, finally, a harmonic analysis procedure by integration for the computation of 
  the geo-potential coefficients. 
  The whole procedure is iterated to recover the signal frequencies cancelled out by the 
  Wiener orbital filter and to improve the rotation from gradiometer to local orbital 
  reference frames.
- The full error covariance matrix of the estimated spherical harmonic coefficients is 
  derived by Monte Carlo simulations.

References:
- A GOCE-only global gravity field model by the space-wise approach.
F. Migliaccio (1), M. Reguzzoni (1), A. Gatti (1), F. Sanso (1), M. Herceg (2).
(1) DIIAR, Politecnico di Milano, Italy.
(2) DTU Space, National Space Institute, Copenhagen, Denmark.
Proceedings of the 4th International GOCE User Workshop, 31 March - 1 April 2010, Munich.
- First GOCE gravity field models derived by three different approaches.
R. Pail, S. Bruinsma, F. Migliaccio, C. Foerste, H. Goiginger, W.-D. Schuh, E. Hoeck,
M. Reguzzoni, J.M. Brockmann, O. Abrikosov, M. Veicherts, T. Fecher, R. Mayrhofer,
I. Krasbutter, F. Sanso, C.C. Tscherning.
Journal of Geodesy, in print.
See also: earth.esa.int/GOCE