GOCE data overview
GOCE gathered data for over four years to map the Earth's gravity field with unprecedented accuracy and spatial resolution. So far, the mission has realised no less than four models of the geoid, each more accurate than the last.
This has provided users worldwide with well-defined data products that are instrumental in advancing science and applications in a broad range of disciplines. These range from geodesy, geophysics and surveying to oceanography and sea-level research. All products are available free of charge to scientific and non-commercial users.
There are a number of steps that are involved in turning the raw data gathered by the GOCE satellite into a product suitable for the users worldwide. This part of the mission involves the 'ground segment', which is essentially made up of three main elements – the satellite control element, the processing element and the archiving element, as well as services to provide users with the data.
GOCE was controlled and operated by the Flight Operations Segment (FOS) at ESA's European Space Operations Centre (ESOC), in Darmstadt, Germany. From here, the health and status of GOCE was monitored and commands generated and up-linked to the satellite.
GOCE data flow
Raw data were down-linked from GOCE to the ground station in Kiruna, northern Sweden, which is suitably located for GOCE's near-polar orbit.
On receipt, the data were immediately forwarded to the FOS in ESOC which then linked the data through to the Payload Data Ground Segment (PDGS) at ESA's Centre for Earth Observation (ESRIN), in Frascati, Italy. Here, through a process of calibration and validation the data underwent an important transformation from telemetry to Level-1b data products.
Level-1b data products are the time series of converted, calibrated and validated measurements taken by GOCE. They consist mainly of the gravity gradients in the local satellite reference system and the orbit data (Satellite-to-Satellite Tracking observations, positions and velocity) in an Earth-fixed coordinate system. In addition, satellite data such as the attitude of the spacecraft and other housekeeping data complete the Level-1b data.
These data are subsequently processed to Level-2 through the High-level Processing Facility (HPF). Under ESA's control, 10 European universities and research facilities that have complementary expertise in gravity and geodesy-related science fields, have joined together to operate the HPF.
There are three parallel methods used for gravity field determination – this cross-validation ensures the high quality of the GOCE gravity field product.
In addition, two complementary strategies employed to derive the orbit provide the possibility to validate the solutions against each other.
The Level-2 data are the fundamental products are available to users worldwide.
They consist of a spectral representation of the gravity potential on a sphere, gridded values of geoid heights and gravity anomalies, including error information and calibrated gravity-gradients in different reference frames.
Access GOCE data at: Earthnet Online - GOCE technical site
For general opportunities to obtain Earth observation data please visit: ESA's Earth Observation Principal Investigator Portal