About EGG

GOCE Geoid
New GOCE geoid

The EGG (Electrostatic Gravity Gradiometer) on board GOCE was a three-axis diagonal gradiometer, based on three pairs of electrostatic servo-controlled accelerometers and had a double role on the GOCE mission. It provided the gravity gradient measurements, mapping Earth's geoid to a highly accurate level. This opened a window into Earth's interior structure, as well as the currents circulating within the depths of its oceans. It was also used as the main sensor in the DFACS (Drag Free Attitude Control System), so if the common mode acceleration in flight direction was not zero, the DFACS responded by either increasing or decreasing the ion engine thrust to maintain the spacecraft in near-freefall conditions.

The EGG instrument was designed and developed at ONERA (Office National d'Etudes et de Recherches Aérospatiales) and manufactured at Thales Alenia Space, France.

The GOCE mission was launched on 17 March 2009 from the Plesetsk Cosmodrome, Russia and came to an end in late 2013.


EGG Data


Download data from the GOCE mission through the ESA GOCE Online Dissemination Service. The data is freely available to registered users.


All GOCE Level 1b and Level 2 products, in accordance with ESA Earth Observation Data Policy, are freely available to users.

See the GOCE product descriptions to learn more about what the products offer:



A number of tools are available for visualising, processing and analysing GOCE data.

GOCE Level-1b and Level-2 XML Parser

The L1b-L2XML parser is capable of importing data into existing applications, by transforming GOCE products from ESA's Earth Explorers file format standards into other common formats.

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GOCEPARSER is an easy-to-use tool for extracting the GOCE Level-1b and Level-2 data from the XML products into a plain text file in columnar format.

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The GOCEXML2ASCII parser is a very fast and memory-efficient XML to ASCII converter for GOCE Level-2 EGG_NOM and SST_PSO data.

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GOCE Level-1b Matlab Readers

Use this starting package to learn how to build simple Matlab routines which can read Level-1b GOCE products.


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Special Datasets and Processor Releases

The following GOCE special datasets are available:

  • GOCE+ Thermospheric data: Thermospheric density and crosswind data products derived from GOCE data
  • GOCE+ Gravity Gradients and GRIDS: Output from the ESA-funded GOCE+ GeoExplore project, which used other satellite gravity information in combination with GOCE data
  • GOCE Re-entry dataset: A special dataset, covering the 20 days of the GOCE re-entry phase in 2013, from 20 October to the end of mission on 11 November
  • SSTI ANTEX data: Antenna Phase Centre Variations (PCVs) are available for both Main (SSTI-A) and Redundant (SSTI-B) antennas

Learn about the processor releases and available baselines for EGG data.

EGG Cal/Val

The goal of performing GOCE Calibration and Validation activities was to quantify the mission’s system response (calibration), to verify the performance by comparison with independent sources of data (validation), and in doing so to assess and quantify uncertainties in the measurements.

EGG Quality Control Reports

GOCE Quality Control Reports are available in three different varieties covering quality monitoring of science and calibration products, providing monthly overviews of the health of the EGG instrument and product quality, and any anomalies that may affect the quality of data acquired.