The MetOp satellites are monitored and controlled via the EUMETSAT Polar System (EPS) Command and Data Acquisition (CDA) station located on the island of Spitsbergen in Svalbard (N). This high northern latitude position of 78º N benefits from the close proximity of orbit tracks at the poles and ensures visibility and commanding by the CDA for all MetOp daily orbits i.e. there are no blind orbits. Visibility profiles allow contact periods varying between 4 and 12 minutes with a typical period of better than 10 minutes.

An S-band command and control space-to-ground link is used for MetOp telecommand up-link and satellite housekeeping telemetry down-link. Commands can be directly up-linked and executed during visibility periods or up-linked and stored on board for execution later, (so-called time-tagged commands) during the periods of non-visibility (typically 90 minutes).

The EPS mission control centre (MCC) located in EUMETSAT, Darmstadt (D), operates a mission planning system (MPS) that is based on instrument operations driven by user request. The MCC uses the MPS to determine the satellite and payload commands to be up-linked by the CDA and executed on board MetOp during the orbit timeline.

MetOp has on-board pre-programming capabilities for 36 hours and time tag commands are routinely stored in the on-board queue to cover the control of all satellite operations in flight during this period. Consequently, the satellite is fully capable of 36 hours autonomous operations as a contingency measure in case of no ground intervention.

Payload data handling and transmission

The science data from the instrument suite is sent to the data handling avionics in the form of data packets, according to the consultative Committee for Space Data Systems (CCSDS) standard. The instrument data rates cover a wide range from 1.5 Mbps for the Infrared Atmospheric Sounder Interferometer (IASI) instrument, down to 160 bps for the Space Environment Monitor (SEM) instrument. These are combined on board with additional packets to facilitate data exploitation:

• position and time data derived from the GNSS receiver for Atmospheric Sounding (GRAS) instrument Global Positioning system (GPS) functionality
• a copy of the full spacecraft housekeeping telemetry
• a text 'administration message' which is up-linked by ground and stored on board, providing a facility to broadcast information to remote users

All of these data streams are multiplexed and provided on three channels going to an on-board solid state recorder (SSR), the High Rate Picture Transmission (HRPT) and Low Rate Picture Transmission (LRPT) direct broadcast systems.

The SSR has a capacity to store a minimum of 24 GB, which is slightly more than one full orbit of data.