European Data Relay System

The European Data Relay Satellite system will be a constellation of GEO satellites intended to relay information between other satellites and ground stations, to allow full-time communications even with satellites in low-Earth orbit which are often not visible from any European-operated ground station.

It provides a sovereignty role, in that it will no longer be critical to use non-European ground stations to interact with Europe's satellites. More usefully, it will allow direct download from satellites to small terminals, allowing for example rescue workers to see near-real-time satellite imagery of the region where they're working.

The system is being developed as part of the ARTES 7 programme; as of mid-2009 it was still at the specification phase, so it is unclear how many satellites will be involved.

The programme is quite similar to the American Tracking and Data Relay Satellite System which was set up to support the Space Shuttle; it is unclear whether it will have as large a military component as TDRSS.