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Satellite Communications Technology

Full house for EDRS

(13 March 2018 - ESA) The EDRS–SpaceDataHighway has now begun regularly relaying Earth images from Sentinel-2A, which marks the last of four Copernicus satellites in orbit being brought under the EDRS service.

After several months of rigorous testing, the system has added the last ‘colour vision’ Sentinel to the list of Sentinels it serves, bringing the satellite’s vibrant images to Earth faster than ever and completing the full set of four.

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A false-colour image showing part of the Ganges Delta in south Asia, captured by the Copernicus Sentinel-2B satellite and relayed by EDRS-A on 27 October 2017. (contains modified Copernicus Sentinel data (2017), processed by ESA)

The European Data Relay System (EDRS) will be a unique system of satellites permanently fixed over a network of ground stations, with the first – EDRS-A – already in space. These nodes lock on to low-orbiting satellites with lasers and collect their data as they travel thousands of kilometres below, scanning Earth.

EDRS then immediately sends the data down to Europe from its higher position hovering in geostationary orbit at around 35 800 km, acting as a go-between.

This process allows the lower satellite to continuously downlink the information it is gathering, instead of having to store it until it travels over its own ground station. That way, it can send down more data, more quickly.

The first two sets of Earth-observing Copernicus Sentinels-1 and -2 are signed up to this service as EDRS’s anchor customers under an agreement between ESA, the EU as owners of the Copernicus programme, and Airbus as the owner and commercial operator of EDRS.

EDRS’s ability to relay Big Data to Europe in near-real time is extremely valuable for a mission such as Sentinel-2. Its high-resolution images not only help to improve agricultural practices and map changes in land cover, but they also assist in monitoring the world’s forests, detecting pollution in lakes and coastal waters, and contributing to disaster mapping.

Many of these applications rely on imaging the same area in quick succession.

EDRS-A will now begin relaying hundreds of gigabits of these time-sensitive data every day over a single laser beam stretching across space, all while the two satellites are traveling at a relative speed of up to 28 000 km per hour.

This feat of engineering has been tried and tested with Sentinel-2A’s cousins, Sentinel-1A and -1B, who have been imaging Earth since 2014, and Sentinel-2B, who started operations with EDRS on 25 October 2017.

Since using EDRS, the Sentinel-1 constellation has increased the amount of data it produces by around half, with Sentinel-2A and its -2B twin on their way to mapping all of Earth’s landmass every five days, aided by the SpaceDataHighway.

The second EDRS node, EDRS-C, will double the system’s capacity after its launch.

The EDRS–SpaceDataHighway is a public–private partnership between ESA and Airbus, with the laser terminals developed by Tesat-Spacecom and the DLR German Space Administration.