The EPS-SG ground segment allows all Sentinel-5 data to be systematically acquired, processed and distributed. It includes elements for monitoring and controlling the MetOp-SG satellites and for downloading, processing and disseminating data to users. It also has mechanisms for monitoring and controlling the quality of data products, as well as for data archiving.

The EPS-SG ground segment is to be built-up over a number of years; initially handling the first MetOp-SG A satellite on which Sentinel-5 flies and then expanding to include also the parallel operations of the first MetOp-SG B satellite.

The EPS-SG ground segment is composed of a series of EPS-SG specific elements plus a series of multi-mission elements that are common across several EUMETSAT missions. An overview of the EPS-SG ground segment, as currently envisioned, is presented in Figure 5. Note that the diagram is not specific to Sentinel-5 as the high level data flow through the system is the same for all EPS-SG instruments. Within each of the elements, functionality specific to Sentinel-5 will be present (e.g. Sentinel-5 Level 1 processing is contained in the PDAP, etc..).

Figure 5: EPS-SG Ground Segment Overview

The main EPS-SG specific elements are:

• The Payload Data Acquisition and Processing (PDAP) acquires the Ka band signal from the satellites that contains the payload data, including the Sentinel-5 instrument data, and transforms this into Level 1 and Level 2 data sets.
• The Mission Control and Operations (MCO) acquires the satellite's housekeeping telemetry and transmits telecommands, tracking and ranging data on S-band. The MCO supports the planning of the mission, monitors the space segment, and performs the flight dynamics functions. In general EPS-SG instrument planning, including Sentinel-5, is based on orbital dynamics predictions calculated on ground which are translated into instrument observing events scheduled on-board the satellite.

The main EPS-SG multi-mission elements are:

• The data centre element that provides a long-term repository of the archived data sets for all instruments, an interface that allows end-users to have access to data stored in the repository, and servers for the exchange of data with specific parties.
• The dissemination element that provides a series of mechanisms for the rapid delivery of generated data sets to various users. One of these mechanisms is EUMETCast, which broadcasts uploaded data sets via commercial telecommunication satellites to specific users possessing the necessary receiving equipment.
• The system monitoring element that provides both generic event and schedule monitoring functionality as well as generic science data analysis and reporting tools. Where needed the system monitoring element is supplemented by specific functions for an instrument where the generic functionality is insufficient.
• The infrastructure element that provides communication networks, IT storage and backup services, and building infrastructure.

The majority of the EPS-SG ground segment facilities are located at the EUMETSAT headquarters in Darmstadt, Germany. The exceptions to this include data acquisition facilities which are foreseen at polar locations (eg. Svalbard) and the back-up satellite control centre whose location will be physically remote from Darmstadt.

The operations of the Sentinel-5 instrument are performed autonomously. A default set of control tables is stored on-board that contain measurement sequences composed of time tagged instrument configuration identifiers each one representing a particular parameterised state of the instrument (e.g. detector settings,...). When necessary, maintenance procedures allow the measurement sequences on-board to be updated via the MCO.