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The European Data Relay System (EDRS), often called theSpace Data Highway, is one of the most ambitious and transformative programmes undertaken by the European Space Agency (ESA)
It represents a major leap forward in how Europe transmits, processes, and delivers data from space.
EDRS enables near real-time data relay between low Earth orbit (LEO) satellites and the ground via geostationary Earth orbit (GEO) satellites equipped with laser communication terminals. By acting as a relay network in space, EDRS dramatically reduces data latency, from hours to minutes, and increases operational efficiency across Earth observation, security, emergency response, and scientific missions.
Developed under ESA’s Partnership Projects, EDRS was developed with Airbus Defence and Space, with key contributions from DLR, Tesat-Spacecom, OHB, and Avanti Communications. The system showcases the effectiveness of public–private cooperation in bringing advanced European space infrastructure to the global market.
The EDRS vision
Before EDRS, satellites in low Earth orbit could only transmit their data when passing over a ground station, limiting contact time to a few minutes per orbit. This created delays in accessing critical Earth observation data used for applications like disaster management, maritime surveillance, and environmental monitoring.
It was recognised that Europe needed a fast, secure, and autonomous space data relay system. The solution was to use laser communication between satellites in different orbits, connecting a constellation of LEO satellites to geostationary relay nodes, which maintain a continuous line of sight to ground stations.
This vision became the European Data Relay System (EDRS): a network providing continuous data connectivity between orbiting spacecraft and Earth-based users, effectively serving as a fibre-optic link in space.
Technological Foundations
The technological heart of EDRS lies in its Laser Communication Terminals (LCTs), developed by Germany’s Tesat-Spacecom in cooperation with the German Aerospace Center, DLR.
Each LCT uses highly precise optical systems to exchange data via laser beams between satellites separated by up to 45,000 kilometres, achieving transfer rates of up to 1.8 gigabits per second (Gbps). These terminals can lock onto each other with microradian precision, roughly the equivalent of targeting a coin from 1,000 kilometres away.
EDRS also supports traditional Ka-band radiofrequency (RF) links for downlinking data to the ground and for providing redundancy.
This hybrid laser-RF (radio frequency) architecture gives the system the flexibility to operate with a wide range of spacecraft and users, from Earth observation missions like Copernicus Sentinel satellites to crewed spacecraft such as the International Space Station (ISS).
System architecture
EDRS currently consists of two main nodes in geostationary orbit and a network of ground stations:
The ground segment includes Mission Operations Centres in Ottobrunn in Germany and Redu in Belgium, supported by optical ground stations and secure data networks.
Together, these components form a flexible and scalable architecture; designed to support a variety of missions simultaneously, each using different data formats and communication requirements.
Operational Use and Customers
The first operational user of EDRS is the Copernicus Sentinel-1 and Sentinel-2 missions, operated by ESA and the European Commission. These satellites provide radar and optical imagery for environmental monitoring, climate change research, and emergency response.
Through EDRS, Sentinel satellites can downlink data continuously to ground within minutes after acquisition, rather than waiting for the next overpass. This has transformed how Europe manages near real-time applications, such as detecting oil spills, tracking ice movement, and assessing flood damage.
EDRS also supports the International Space Station, by providing high-speed communication for scientific experiments; commercial and governmental users, including military and security agencies, for secure data relay, as well as the Copernicus Sentinel satellites for Earth Observation. It is intended to support future potential lunar communications under ESA’s Moonlight programme.
Strategic Impact for Europe
EDRS strengthens Europe’s technological sovereignty in space communications, giving ESA Member States a secure, independent infrastructure for critical missions.
It also catalyses industrial growth: over 40 European companies participated in EDRS development, creating a robust ecosystem in optical communications and satellite networking. The technologies pioneered by EDRS are now being leveraged in next-generation systems like ESA’s High Throughput Optical Network (HydRON) and Quantum Key Distribution (QKD) missions.
Environmentally, EDRS improves the responsiveness of Earth observation systems, helping authorities make faster decisions during natural disasters and humanitarian crises.