Laser instead of radio: Europe's high-speed offensive

Faster and more secure data exchange - even in remote areas: this is what laser communication promises. With his Starlink network, tech mogul Elon Musk has been working for several years to install a network for comprehensive satellite communication in low Earth orbit. Europe is also striving into these spheres and wants to become independent of providers and suppliers from abroad in the field of laser communication. Technological sovereignty is the goal, especially in critical infrastructures, such as in the area of security and civil protection.

The European Space Agency ESA is therefore promoting European research institutions and companies in the research and development of their own systems and competencies with its ScyLight programme (Secure and Laser communication technology). One of these companies implementing a development project for technology provision as part of the ScyLight programme is Tesat. The company, based in Baden-Württemberg, has been building laser communication systems for many years, including the SCOT135 system, a scalable optical communication terminal specifically developed for use in medium (MEO) and geostationary Earth orbit (GEO).

Every hour of manufacturing time counts

For this laser terminal, Fraunhofer researchers from Jena have developed a space-robust transmission and reception telescope over three years, which, unlike scientific-oriented telescopes, can be produced not only in small quantities but also in series. "Our goal was to develop a robust and cost-effective series product," explains Dr. Henrik von Lukowicz, the project manager and head of the Optical and Mechanical System Design department at the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF). "For systems that are to be manufactured in large quantities, every hour of manufacturing time counts in the end."

The SCOT135 system is expected to achieve up to 100 Gbit/s in bandwidth and bridge distances of up to 80,000 km with the telescope developed in Jena. "In combination with terminals that are built in large numbers and prospectively linked to an inter-satellite network, this is new," says von Lukowicz. "For this, we have developed a universally applicable telescope that is both a transmission and reception unit."

Robust design for demanding conditions

When used in space, the telescope must withstand the environmental stresses there as well as the stresses caused by the operation of the system itself: "In laser communication systems, relatively high laser powers are achieved. Here, up to 50 watts are exerted. For a space telescope, that is relatively high power propagated through the system," explains von Lukowicz. "This leads to heat developments that can cause changes in the optics. But of course, the system's performance must not be impaired by this. Thermal management was therefore a particularly important point for our design."

In addition to thermal regulation, various expertise from the Fraunhofer IOF flowed into the design development, as it was built up based on years of experience with space projects at the institute. "This involves various questions: For example, how to manufacture particularly lightweight components for space flight, methods for resilient adjustment of the components, and fine structuring on the optics for precise performance," explains von Lukowicz.

Design at Fraunhofer IOF, manufacturing at Spaceoptix

The design of the telescope was developed by researchers at the Fraunhofer IOF in Jena. The manufacturing is handled by the New Space company Spaceoptix, a spin-off of the Fraunhofer IOF, at the Isseroda site in Thuringia. Five systems have already been manufactured at Spaceoptix for Tesat. In the future, a further 50 units can be produced each year.

The first flight models were successfully delivered to Tesat in June. "The transmitter and receiver telescope developed in Jena is an important key component for our SCOT135 system. The collaboration with Fraunhofer IOF and Spaceoptix has brought us a big step closer to our goal of becoming a central enabler for European laser communication not only in near-Earth laser-based satellite networks but also in medium and geostationary orbits," summarises Dr. Frank Heine, chief developer for laser systems at Tesat.