All lanes open on the Space Data Highway

From high in geostationary orbit EDRS-A has a clear view of lower-flying Sentinels and of its own ground station (ESA)

13 March 2018

The first phase of Europe’s EDRS system for high-speed download of data from Earth observation missions is fully functional, with the Sentinel-2A satellite now using the service regularly after commissioning. It joins its sister spacecraft, Sentinel-2B, and the two Sentinel-1s in transmitting imagery via a high-capacity laser link to a relay satellite in geostationary orbit, which in turn sends it to the ground.

The system is already transforming the speed of access to satellite data. Normally, satellites like the Sentinels – flying in low-Earth orbit roughly around the poles – have a download window of maybe 10 minutes per 100-minute orbit, when they are in view of a ground station. But for much of their orbit those satellites in LEO can “see” a relay satellite in a 36,000km-high geostationary orbit, and that relay satellite is in constant view of its ground station.

The result is a quadrupling of the time per orbit that an observation satellite can transmit data – and the laser link is stunningly fast, up to 1.8Gbit/s. Communicating with satellites in LEO in near-real time promises to vastly enhance the value of images of, for example, disaster scenes.

For good reason, EDRS – the European Data Relay System – is also called the “Space Data Highway”, and has been likened to a shift from copper cables to fibre optics on a terrestrial internet connection. According to the European Space Agency, EDRS has increased the amount of data produced by Sentinel-1A and -1B by more than a third. Right now, there is just one relay payload in orbit, EDRS-A, which is a hosted payload aboard the Eutelsat-9B communications satellite launched in January 2016. A second relay satellite, EDRS-C, will be launched in late this year or early in 2019; having two units in orbit over central Europe will double the system’s daily capacity to about 80 terabytes of acquired data and also extend the geographic coverage and redundancy of the system.

Airbus, which runs EDRS as a public-private partnership with ESA, says it is willing to expand the system further, with a third node, ERDS-D, to be positioned over the Asia-Pacific region. A third relay would provide global coverage and attract more and private customers. Sentinels-1 and -2 are the “anchor” customers for the Airbus-operated service, but it is expected to be a standard feature of Europe’s Copernicus Earth observation platforms. And, aircraft or unmanned platforms equipped with a suitable laser terminal could also tap into EDRS.

According to Germany’s DLR space agency, which is controlling the -A and -C satellites from its operations centre at Oberpfaffenhofen, the International Space Station will be able to communicate with the ground by EDRS, possibly this year.

This Sentinel-2 image from 2 March 2018 shows Amsterdam and the IJmeer and Markemeer freshwater lakes covered by a thin layer of ice – too thin for skating, though the cold snap saw blades on some canals in the city (ESA)