ESA Notches 100th High-speed Laser Link between Satellites 48,000 Kilometers Apart 

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PARIS — The European Space Agency on Aug. 5 said it had successfully conducted 100 high-speed laser links between its Sentinel-1A radar Earth observation satellite in low Earth orbit and the AlphaSat satellite in geostationary orbit.

The tests offered further confirmation of the basic soundness of a technology that the 22-nation ESA is trying to develop into a commercial business in a partnership co-funded with Airbus Defence and Space. For the moment, the effort is being slowed not by the technical performance of the laser communications, but by delays in the launch of geostationary satellites carrying the laser terminals.

The agency said communications since testing began in November have been established using as little as 1.1 watts of power, with up to 1.8 gigabits per second of Sentinel-1A synthetic aperture radar data delivered to AlphaSat at a distance of up to 48,000 kilometers.

The 100th link, established within 50 seconds on July 14, maintained stable bit-error-free communications for 10 minutes, ESA said.

Sentinel-1A’s orbit is 693 kilometers in altitude, inclined 98.2 degrees from the equator. AlphaSat, located over Central Africa at 24.8 degrees east in geostationary orbit, was launched in 2013. Its commercial L-band payload is operated by mobile satellite services provider Inmarsat of London.

The 22-nation ESA – which financed much of AlphaSat’s development along with Inmarsat – operates several technology demonstration payloads, including the laser communications terminal, which was financed by ESA and the German Aerospace Center and built by Tesat Spacecom of Backnang, Germany.

The Optical Communication Terminal is one of four Technology Demonstration Payloads carried by Alphasat. It relays Earth observation data from low-Earth orbit (LEO) to geostationary orbit (GEO) through laser transmission. A Ka-band transmitter then forwards the data to a ground station. Credit: ESA
The Optical Communication Terminal is one of four Technology Demonstration Payloads carried by Alphasat. It relays Earth observation data from low-Earth orbit (LEO) to geostationary orbit (GEO) through laser transmission. A Ka-band transmitter then forwards the data to a ground station. Credit: ESA

The European Commission has agreed to be the anchor customer for the European Data Relay System (EDRS), which Airbus wants to transform into what it calls the SpaceDataHighway to speed Earth observation to users.

Airbus has two laser communications payloads on geostationary-orbit satellites yet to be launched. The first, aboard Paris-based Eutelsat’s Eutelsat 9B commercial telecommunications satellite, has been delayed by the grounding of Russia’s Proton rocket but is now tentatively scheduled for launch late this year.

The second, still under construction, is scheduled for launch in 2017. Airbus ultimately wants to place a final laser payload aboard a commercial telecommunications satellite to be stationed over the Asia-Pacific region to offer global coverage to prospective customers including the U.S. Defense Department and its fleet of unmanned aerial vehicles.