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GOCO: Gravity Observation Combination

The main objective of the GOCO initiative is to compute high-accuracy and high-resolution global gravity field models from complementary gravity data sources:

  • satellite gravity missions GOCE, GRACE, GRACE-FO and CHAMP, and SLR data (satellite-only models of the GOCO-S series)
  • plus terrestrial gravity field and satellite altimetry data (combined models GOCO-C)

The combination is done by superposition of full normal equations and applying optimized relative weighting strategies.

GOCO has been initiated in the frame of ESA's GOCE Data AO (project no. 4248), with the project partners responsible for the GOCE-only time-wise (TIM) models as the nucleus.

The GOCO consortium is composed of the following institutions, co-ordinated by the Institute of Astronomical and Physical Geodesy at Techinical University of Munich:

 More information can be found under goco.eu.

The satellite-only gravity field model GOCO2025s

GOCO2025s is a satellite-only, global gravity field model up to degree and order 300, with constrained secular, annual, and semi-annual variations up to degree and order 200.

GOCO2025s is the latest release in the Gravity Observation Combination (GOCO) series. The model is based on satellite data collected between 2002 and 2024 (inclusive). Contributing satellite missions include GOCE (TIM6 gradiometer observations), GRACE and GRACE-FO (KBR and LRI observations), as well as kinematic orbits from CHAMP, GOCE, Swarm A/B/C, Sentinel-1A/1B/2A/2B/3A/3B/6A, TerraSAR-X, TanDEM-X, and satellite laser ranging observations (ITRF2020 reference frame) to AJISAI, BLITS, LAGEOS-1, LAGEOS-2, LARES, LARES-2, LARETS, Starlette and Stella. The temporal variations include observations up to degree and order 150 and are regularized using isotropic noise, separated by land/ocean masks up to degree and order 200. The combination of individual data sources is based on the full system of normal equations, with relative weighting among the constituents determined via variance component estimation.

The individual files of GOCO2025s contain (available at https://doi.org/10.3217/f48p8-8h651):

  • "GOCO2025s.gfc": Static and time-dependent gravity field coefficients in terms of spherical harmonics and their respective uncertainty information. An algorithm on how to compute a gravity field functional at a specific time can be found in the header.
  • "GOCO2025s_normalEquation.snx": All parts of the normal equation system of the static gravity field, including the original normal equation, the vector of the right hand side, apriori values of the unknown parameters, the normal equation of the applied constraints and the resulting solution vector.
  • "AOD1B_RL0X_included_in_GOCO2025s.gfc": The gravitational potential of non-tidal atmospheric and ocean masses already included in GOCO2025s. In order to use GOCO2025s together with AOD1B RLO6 or RL07, the respective files have to reduced beforehand.

When using the data please cite:

Öhlinger, F., Mayer-Gürr, T., Krauß, S., Dumitraschkewitz, P., Süsser-Rechberger, B., Strasser, A., Tieber-Hubmann, C., & Brockmann, J. M. (2025). The satellite-only gravity field model GOCO2025s [Data set]. Graz University of Technology. https://doi.org/10.3217/f48p8-8h651

Contact
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Torsten Mayer-Gürr
Steyrergasse 30/III
8010 Graz
Austria
Tel: +43 316 873-6359
Fax: +43 316 873-6845
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Felix Öhlinger
Steyrergasse 30/III
8010 Graz
Austria
Tel: +43/316/873- 6333
Fax: +43/316/873-6845
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Sandro Krauss
Steyrergasse 30/III
8010 Graz
Austria
Tel: +43/316/873- 6344
Fax: +43/316/873-6845
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Patrick Dumitraschkewitz
Steyrergasse 30/III
8010 Graz
Austria
Tel: +43/316/873- 6333
Fax: +43/316/873-6845
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Andreas Strasser
Steyrergasse 30/III
8010 Graz
Austria
Tel: +43/316/873-6347
Fax: +43/316/873-6845
andreas.strassernoSpam@tugraz.at

Cornelia Tieber-Hubmann
Steyrergasse 30/III
8010 Graz
Austria
cornelia.tieber-hubmannnoSpam@tugraz.at