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The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is constructing a new research observatory on the Empfingen Innovation Campus. The DLR Institute of Technical Physics intends to use it to determine the trajectories and properties of objects in near-Earth orbits as quickly, accurately and reliably as possible. This is the only way to avoid potential collisions between space debris and satellites, for example. On 3 and 4 March 2021, the construction work took a decisive step forward. A crane first lifted the dome onto the 10-metre-high cylindrical support tower. The dome is five metres tall, has a diameter of 7.5 metres and weighs approximately five tonnes. It was pre-assembled on the ground before being lifted in one piece and installed. This was followed by the centrepiece of the project, the specially designed telescope weighing 6.5 tonnes, which was manoeuvred into place in two stages.

Precision in construction and for future measurements

"We have been really thrilled to watch this crucial step in the construction of the research observatory take place before our very eyes. Our partners did a meticulous job of lifting, positioning and installing the dome and telescope. This unique high-tech facility will soon be ready to start tracking down space debris, a feat that requires the utmost precision," says Thomas Dekorsy, Head of the DLR Institute of Technical Physics.

A unique research and development facility for the detection of space debris

The dome has a slotted design and is synchronised to rotate with the telescope. It is only open by approximately two metres in the viewing direction. To perform this task, the dome is mounted on rollers and driven by a motor. The large-scale optical telescope has three mirrors, the largest of which measures 1.75 metres across. This makes the telescope one of the largest of its kind in Europe. It can also rotate at up to six degrees per second. Combining the large primary mirror with such a high tracking speed has required technological solutions that were far from easy to implement. However, incorporating both aspects is necessary in order to observe as large an expanse of sky as possible, and to simultaneously detect, locate and analyse objects as little as 10 centimetres across while they are moving at 28,000 kilometres per hour.

Specialist company Astro Systeme Austria (ASA) designed and manufactured the telescope and support tower as Prime Contractor. Italian construction firm Gambato, which specialises in astronomical buildings, assisted with the dome. The outer structure and the telescope each have their own foundations and base to ensure that the telescope is as stable as possible and prevent the transference of vibrations and wind loads. The telescope base also contains a special tube, referred to as a Coudé path, which allows the DLR team to integrate special lasers into the system and use laser ranging to determine the distance of objects in near-Earth orbits very precisely. With these data, possible collisions of satellites can be predicted more accurately, and evasive manoeuvres better planned. This work contributes to the safe use of space and is supported by the Security Programme Coordination organisation at DLR.

First of all, however, the observatory has to be completed in stages over the coming months and put into operation. The telescope will receive its 'first light' in the next few weeks. Among the DLR researchers, however, all eyes will be on the site acceptance test, which will establish that the telescope is fully functional. To do this, it must survey 10 objects in low Earth orbit, such as satellites, with the greatest possible precision. The official inauguration is planned for autumn 2021. Funding of approximately 2.5 million euro was provided by DLR and the German Federal Ministry for Economic Affairs and Energy (Bundesministerium für Wirtschaft und Energie; BMWi).