Updated, February 1 @ 9:15 GMT: The first EDRS node has successfully launched into space and into its correct geosynchronous orbit. Now we need to wait a few days to see if everything works as planned.

Original story

In the early hours of Saturday morning, a Russian Proton rocket will lift off from Baikonur in Kazakhstan, carrying the first node in what the European Space Agency (ESA) calls the "SpaceDataHighway."

The system will make it possible for satellites and other craft travelling in low-Earth orbit (LEO), including the International Space Station (ISS) and even space drones, to send vast quantities of data back to ground with minimal delay. Currently satellites are only able to send back data during around a tenth of their orbit time, when they have line-of-sight with their ground stations. (The ISS is a bit special: it uses multiple base stations so that it rarely goes out of coverage.)

The European Data Relay System (EDRS) nodes will be able to relay those signals from much farther out in geostationary orbit, vastly increasing that window of opportunity—four-fold with just the first node, and ultimately to near-constant coverage. At 1.8Gbps, the link will also provide faster transfers than currently possible, sending up to 50TB per day.

The launch of the EDRS-A node—a payload piggybacking on an Airbus-built satellite—will establish the commercial market in space laser communications. NASA is working on similar technology, but the Europeans are getting theirs out there first, with the initial users being ESA and the European Commission's Earth-monitoring Sentinel-1 and Sentinel-2 satellites.

"The system we're starting now is world-leading in that domain," said Michael Witting, the EDRS project manager. "Essentially EDRS came into being because the technology was ripe and because we had the chance to stimulate the commercial market by having these anchor customers in the Sentinel satellites."

Sentinels

The Sentinels make for model customers. This is not a system for holding telephone conversations—it's for getting high-resolution images of, for example, floods, earthquakes and forest fires back to base as quickly as possible, to help people on the ground.

EDRS will offer a healthy bandwidth, thanks to its use of laser communications between the client satellite and the relay node. A Ka-band radio link will complete the journey down to one of EDRS's European ground stations. "The link to the ground is designed [to] support the full speed of the laser link," said Witting. After that, it's up to the ground systems to process the imagery as fast as they can.

Even better from a bandwidth perspective is that the 1.8Gbps link won't be shared. Customers cannot be served concurrently: the node's laser cannot point at different satellites in different orbits at the same time, so satellites will typically pre-book downlink sessions of around 10 minutes each.

German engineering

Developed by the German telecommunications satellite firm Tesat, the laser communications terminals on EDRS-A and its EDRS-C twin (a dedicated satellite that will go up in mid-2017) represent quite the engineering feat. "You have to develop a terminal that is able to communicate with a counter terminal over distances of up to 45,000km, between two objects moving at 7,000km per hour," said Witting.

"It's a laser beam; you have to point it accurately. It's the same as taking a torch in Europe and pointing at a two-euro coin in New York. That's one of the main challenges for developing the laser communication terminal, but also developing the satellite—it has to be stable enough to allow that kind of accuracy."

EDRS, which is built and operated by Airbus Defence and Space, also comes with a strong security twist, from both technical and strategic standpoints. First off, the system's ground stations are all in Europe—Weilheim in Germany, Harwell in England, and soon Matera in southern Italy. As today's ground stations are typically in polar regions, in countries like Canada, the US, and Russia, EDRS provides the comforting option of independence.

It's also impossible to jam and extremely difficult to listen into the transmissions, Witting claimed. The links between the EDRS nodes and Earth will be highly encrypted, and the laser links between the nodes and their customers will also be pretty secure.

"It's communicating with a laser beam… that only has a diameter of 300 metres," he said. "If you wanted to eavesdrop on it, you'd have to fly in-between the two communicating satellites within that accuracy, which is basically impossible." As the counter terminal can only receive one beam at a time, jamming is also off the menu.

The narrowness of infrared waves provides another advantage over radio communications—the terminals can be much smaller with lower power requirements, allowing for more petite satellites that can provide huge cost savings. There's also the matter of avoiding the bottlenecks that are forming on traditional satellite communications bands, as more and more satellites crowd the skies.