GOCE Gravity Field Model

Direct Solution - Second generation

Model Characteristics
GOCE Input Data:
- Gradients: EGG_NOM_2
- Orbits: SST_PKI (kinematic orbits)
- Attitude: EGG_IAQ_2C
- Data period: 20091101T000000:20100630T235959
The full list of input data to this direct-approach model is provided in the IHD file.

A-priori Information used:
- A-priori gravity field information applied Background model: ITG-Grace2010s
(Mayer-Guerr et al. 2010) up to d/o 150

Processing Procedures:
- The orbit positions of the GO_CONS_SST_PKI product are used as observations in a
reduced-dynamic orbit computation procedure, which uses the measured common mode
accelerations too. "SST"-Normal equations are computed to d/o 150.
- The gravity gradients are processed without applying the calibration factors. The
observation equations are filtered with a 10-125 mHz bandpass filter, and
subsequently "SGG" normal equations to d/o 240 are computed individually for the
gradient components Txx, Tyy and Tzz.
- The SST and SGG normal equations are accumulated with the following relative
weights: SST 0.00001, Txx, Tyy and Tzz 1.0. The contribution of the SST
normal equation was taken only to d/o 130.
- To overcome the numerical instability of the normal equations due to the polar gaps
a spherical cap regularization in accordance to Metzler and Pail (2005) was iteratively
computed to d/o 240 using the GRACE gravity field model ITG-Grace2010s (Mayer-Guerr et
al. 2010) to d/o 150.
- The solution was obtained by Cholesky decomposition of the accumulated normal

Specific features of resulting gravity field:
- The model is more accurate than state-of-the-art GRACE models for degrees 130-150
and up, but less accurate for the lower degrees.
- The model is a satellite-only model. Due to the applied polar gap stabilization
it is mainly based on GRACE data up to d/o 150
Processing details are presented in Bruinsma et al. 2010 and Pail et al. 2011.

- Bruinsma S.L., Marty J.C., Balmino G., Biancale R., Foerste C.,
Abrikosov O. and Neumayer H, 2010, GOCE Gravity Field Recovery by Means
of the Direct Numerical Method, presented at the ESA Living Planet Symposium,
27th June - 2nd July 2010, Bergen, Norway; See also: earth.esa.int/GOCE
- Mayer-Guerr T., Kurtenbach E. and Eicker A., 2010, The Satellite-only Gravity Field
Model ITG-Grace2010s, http://www.igg.uni-bonn.de/apmg/index.php?id=itg-grace2010
- Metzler B. and Pail R., 2005, GOCE Data Processing: The Sperical Cap Regularization
Approach, Stud. Geophys. Geod. 49 (2005), 441-462
- Pail R., Bruinsma S., Migliaccio F., Foerste C., Goiginger H., Schuh W.-D, Hoeck E,
Reguzzoni M., Brockmann J.M, Abrikosov O., Veicherts M., Fecher T., Mayrhofer R.,
Krasbutter I., Sanso F. and Tscherning C.C., 2011, First GOCE gravity field models
derived by three different approaches. Jounal of Geodesy, in review.