A new era in space observation has begun. The German Experimental Space Surveillance and Tracking Radar (GESTRA) system, which has been developed and constructed by the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) on behalf of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Space Administration, received its first signals reflected by objects in space on 27 November 2019.
In addition to the use of the latest electronic components, what makes GESTRA particularly special is its transmission and reception technology. The complex radar system employs 256 individual, electronically controlled antennas. The phase-controlled antennas (phased array technology) operate digitally and their performance is currently unsurpassed worldwide. The digital control system allows the beam direction to be changed within a few milliseconds and the radar signal to be transmitted so that it is highly focused in the direction of an object. The resulting return signal is then accurately recorded by the receiving system.
In addition, the antenna array can be rotated in any direction using a mechanical steering system. This enables space to be monitored flexibly, in all directions. Each antenna element has its own water-cooling system, ensuring particularly high radar performance, while also increasing the sensitivity of the system. This means that GESTRA is not only highly dynamic when it comes to the observation of objects in space, but also extremely sensitive.
The transmitter and receiver systems are housed in two separate containers, enabling them to be transported to different locations. This combination of mobility and digital technology makes GESTRA unique. The system is currently at the FHR site in Wachtberg and will be transported to its ultimate destination, at Schmidtenhöhe near Koblenz, after it undergoes its final tests. "With GESTRA, one of the world's most modern radar systems for space observation will soon be available to the German Space Situational Awareness Centre (GSSAC) in Uedem," says Thomas Eversberg, GESTRA Project Manager at the DLR Space Administration.
At GSSAC, DLR's civilian staff are working with members of the German Air Force to integrate GESTRA, which is operated jointly by the DLR Space Administration and the Air Force. The radar observations will be used at GSSAC to create a catalogue of objects in Earth orbit. GSSAC needs such a catalogue in order to protect national space assets from collisions with other objects in space.
Once GESTRA has been commissioned, GSSAC will be responsible for controlling the system. All of the data from the experimental radar will be collected there. The orbits of objects in space will be determined and this information will be made available to users at universities and research institutions in Germany. In addition to the creation of a German orbital data catalogue, GESTRA will also be involved in the European Space Surveillance and Tracking (EUSST) project. Germany has the task of processing the measurement data from the sensors that contribute towards EUSST, including GESTRA, to create a European orbit data catalogue. Simulations have shown that the technology employed by GESTRA can play a major role in the European sensor architecture.
This new technology successfully demonstrated its capabilities in recently conducted tests. "We are proud that we have succeeded in working with our colleagues and suppliers to build such a complex system and have now managed to survey some objects in space," says FHR Project Manager Helmut Wilden. DLR, FHR and a number of subcontractors can be proud of their successful collaboration to create this unique, state-of-the-art system. In the near future, GESTRA will make a significant contribution to space security at national, European and international levels.
Space debris as a threat
Several thousand satellites, spacecraft and other objects are travelling in Earth orbit. However, this region also contains hundreds of thousands of pieces of space debris. In total, this amounts to approximately 8000 tonnes of material. The majority of the debris – approximately 75 percent – is at altitudes of between 200 and 2000 kilometres, referred to as 'low-Earth orbit' (LEO). There is therefore a high risk of collisions with space infrastructure. The International Space Station (ISS), which is orbiting Earth at an altitude of approximately 400 kilometres, is affected by this. A constant supply of reliable data on the situation in space is required in order to prevent collisions. This has created the need for radar systems such as GESTRA.
GESTRA was developed by the Fraunhofer Institute for High Frequency Physics and Radar Technology (FHR). Finance was provided by the DLR Space Administration using funds from the German Federal Ministry of Economic Affairs and Energy (BMWi). In future, the radar system will be operated by the German Space Situational Awareness Centre in Uedem, which is financed by the BMWi and the German Federal Ministry of Defence (BMVg). The BMVg will fund the operation of GESTRA.