DLR: Green light for the first dedicated satellite for the European 'space data highway'
The European Data Relay Satellite System (EDRS), also known as the 'space data highway', is setting a new standard in real-time data transfer. The innovative laser nodes can transport data volumes of up to 1.8 gigabits per second to Earth, with minimal delay. The programme's first communication node, EDRS-A, was launched on 29 January 2016, and is already providing relay services for data transfer from the four Sentinel satellites of the EU Copernicus Earth observation programme. The advantage is that the Earth observation satellites can deliver significantly more data to the ground faster and thus also better serve the end user (see info box). The first dedicated satellite in the series – EDRS-C – was designed, constructed and tested in Germany. It has been thoroughly tested over the past 11 months and will begin its journey to Europe’s spaceport in French Guiana in June 2019. It will be launched into a geostationary orbit on 24 July 2019 on board an Ariane 5 launch vehicle.
EDRS is a public-private partnership between the European Space Agency (ESA) and the primary industrial contractor, Airbus. With a programme participation of approximately 235 million euro (61 percent), Germany is the main contributor to this ESA programme. The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Space Administration manages the German contributions to ESA on behalf of the Federal Government, using funds from the Federal Ministry for Economic Affairs and Energy.
EDRS-C – 'made in Germany'
The EDRS-C satellite is considered to be a milestone in the programme. It follows a first experimental laser communications terminal, launched in 2013 on the European telecommunications satellite Alphasat, as well as the operational communications node EDRS-A. The EDRS-C satellite will be the first of its kind in the world. "With EDRS-C, the network will receive its first dedicated satellite. EDRS-C contains a lot of German high technology and follows the strategy of establishing a system provider for telecom satellites in Germany. The German commitment thus supports systems expertise for telecommunications satellites and payloads and secures our technological lead in the field of optical communications," said Walther Pelzer, DLR Executive Board Member responsible for the Space Administration.
Virtually all major German aerospace locations have contributed to EDRS-C. It is the second telecommunications satellite produced by the Bremen-based company OHB and extends the SmallGEO product line of relatively low mass geostationary satellites. The heart of the satellite is the laser terminal. The company Tesat (based in Backnang, near Stuttgart) is not only contributing the necessary technology but has overall responsibility for the EDRS communications payload. This also includes travelling wave tubes produced by Thales in Ulm, the principal European site for radio frequency amplifier elements.
Important subsystems and components of the satellite platform also come from suppliers in Germany. For example, the chemical propulsion system was developed by Ariane Group in Lampoldshausen. Structural elements of the satellite and pressure tank were contributed by the company MT Aerospace in Augsburg. In addition to the star tracker built by Jena Optronik and the reaction wheels produced by Collins Aerospace, other important components of the attitude and orbit control system were also ‘made in Germany’.
The extensive satellite tests prior to launch were carried out at IABG and Airbus in Ottobrunn. Airbus in Ottobrunn already operates EDRS-A and will also take over mission control for EDRS-C after launch; it is thus able to offer a globally unique service. The German Space Operations Center at the DLR site in Oberpfaffenhofen has been commissioned by Airbus to control the payloads and the EDRS-C satellite. DLR has invested 8.7 million euro from research funds to the development of the EDRS ground segment and the preparations for its operation. The Bavarian State Ministry of Economics and Media, Energy and Technology provided 7.5 million euro.
EDRS-C – a European project
Despite the large German share, EDRS is a European project in which 14 ESA member states are participating. With the Earth observation programme 'Copernicus', EDRS has an important anchor customer in Europe. In addition, the optical communications payload on EDRS-C does not require all of the resources; the satellite also hosts a payload for the British satellite operator Avanti. During the design phase of the satellite, several interested parties submitted tenders in response to a call from ESA. Avanti, with its commercial payload 'Hylas-3', was offered the opportunity for a ride-share on EDRS-C and is therefore also bearing a proportion of the platform and launch costs.
This is how EDRS works
The principle of the European 'space data highway' becomes clear from the interaction of the Sentinel satellites of the European Earth observation programme Copernicus with EDRS. Without EDRS, Earth observation satellites in low Earth orbit can send their data directly to Earth only when they are over a ground station. This is the case for only about 10 minutes in a satellite's 90-minute orbit. In contrast, the EDRS communications nodes remain visible to the Sentinel satellites for much longer – for half their orbital period; that is, for about 45 minutes. Thus, with EDRS data can be sent over a longer period of time. The data are also sent directly to Europe, so that it is not necessary to rely on ground stations outside Europe. The Sentinel satellites use this service daily, and by March 2019, well over one petabyte had already been transmitted in 20,000 satellite connections of this kind.