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In February 2008 a government-to-government agreement between the US and Germany to establish a laser link between two operational satellites in low earth orbit (LEO) ushered in a new chapter in communications history. Germany’s TerraSAR-X radar satellite and the US Defense Missile Agency NFIRE, both equipped with laser communication terminals (LCT) manufactured by Tesat-Spacecom GmbH, established the first successful, stable orbital laser link.

Now, the Tesat LCT 135 makes it possible for users to send up to 1.8 Gbps of data and information over a distance of up to 80,000 km, quickly, securely and entirely free of interference – even when both satellites drift away from each other at absolute orbital speeds of up to 30,000 km/h in different orbits.

Tesat's LCTs are the key technology behind the Airbus SpaceDataHighway, which provides near-real-time data transmission to any location on earth. This system of two geostationary satellites is used to relay data between LEO satellites, spacecraft, airborne platforms and fixed ground stations. Thus Tesat‘s technology enables near-real-time data provision in support of time-critical and data-intensive applications for security or emergency response missions around the world. Another good example of an appropriate application is in the support of global maritime surveillance activities, as in the upcoming Airbus Pléiades Neo constellation.

Tesat can offer LCTs appropriate to a wide range of applications. For LEO applications the SmartLCT can be deployed on smaller, lighter satellites with huge weight and size savings. Offering data transmission over distances of up to 45,000 km, while maintaining the high data rate of up to 1.8 Gbps, the SmartLCT weighs just about 22 kilogrammes.

Tesat currently operates eight LCTs in space – two on geostationary satellites in the SpaceDataHighway and six on LEO satellites. A third geostationary satellite will follow to enable global communications. Altogether, another eight satellites are in production. Thanks to the satellite constellation and laser technology, the information is transferred to earth in less than 15 minutes.

One of the main advantages of satellite communications for government is the jamming-resistant nature of the communications beam which is narrow enough to make it difficult for an adversary to focus jamming on the appropriate point. Since safeguarding and encryption techniques are also in use, user confidence in data security is high.

As part of the so-called ‘Laser Communication Coalition,’ the next step will be connecting unmanned aerial systems (UAS) to this technology. Satellite communications devices mounted on UAS – which will include those manufactured by General Atomics Aeronautical Systems – will be replaced by a new airborne terminal, providing an alternative to Ku-Band. Data transfer will be faster and channeled via higher bandwidth – although project status remains at the proof-of-concept stage for the moment.

A significant user for this laser communications system is France, with many other countries showing interest. Only Germany seems to hesitate, despite the technology having been developed there.

André Forkert

Tesat’s Laser Communication Terminals now power communications networks ready for the severest challenges of defence, security and disaster response missions. (Image: Tesat)

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