Around 90 minutes after GOCE was launched into orbit about 280 km above Earth, it was released by the launch vehicle’s upper stage.
The satellite’s orbit will then decay over a period of 45 days to an operational altitude of about 260 km. During this time, GOCE will be commissioned and the electrical propulsion system checked for reliability in drag-free control.
During operations, the satellite will be monitored, operated and controlled by the Flight Operations Segment (FOS) at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany.
ESOC generates and uplinks commands to programme GOCE’s operations, and processes the housekeeping and instrument data to monitor the health and performance of the satellite and instruments.
For around 20 months, GOCE will gather data to map Earth’s gravity field with unprecedented accuracy and spatial resolution. The final gravity map and model of the geoid will provide users worldwide with well-defined data products. These will be instrumental in advancing science and applications in a broad range of disciplines.
All products will be available free of charge to scientific and non-commercial users. A number of steps have to be taken in order to turn the raw data gathered by GOCE into products suitable for the users worldwide.
This part of the mission is taken care of by the so-called ground segment, which is made up of three main elements – monitoring and control of the spacecraft, data processing and archiving and distribution. Additionally, services to provide users with online data access are part of this.
Raw data are downlinked from the satellite to ground stations in Kiruna (Sweden) and Svalbard (Norway).
Upon receipt, the data are immediately forwarded over a fast network to the FOS in ESOC, which relays them to the Payload Data Ground Segment (PDGS) at ESA’s European Space Research Institute (ESRIN), in Frascati, Italy, where the data undergo an important transformation from telemetry to level-1b data products.
These level-1b data are subsequently processed to level-2, the fundamental products that will be available to users worldwide, through the High-level Processing Facility (HPF).