Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRThe nationwide surveillance of large swathes of space to determine valuable orbital data: these are the capabilities of the Space Surveillance Radar GESTRA. It tracks objects in low Earth orbit – whether satellites or space debris – and provides reliable, precise data as part of a Europe-wide sensor network to the joint Space Situational Awareness Center (WRLageZ) of DLR and the Bundeswehr. With a second receiver, the resolution will further increase in the future.
Whether satellites, debris, or bolts — millions of objects drift through space. Each one can become a dangerous projectile and damage or even destroy active satellites. Knowing the objects’ positions is all the more important. If a collision threatens, satellites can perform an avoidance maneuver.
The semi-mobile Space Surveillance Radar GESTRA, short for German Experimental Space Surveillance and Tracking Radar, provides valuable support here. It detects and tracks objects in their orbits, which are subsequently cataloged. GESTRA was developed by Fraunhofer FHR on behalf of the German space agency in the DLR for the WRLageZ.
GESTRA detects up to 6,000 objects per day
In 2023, GESTRA demonstrated its capabilities for the first time in a functional demonstration. With impressive results: over 200 objects were detected on average per hour, including small objects like CubeSats at distances of several hundred kilometers. Visible objects included numerous Starlink satellites as well as the Orbiter Oneweb-0240 (altitude around 1,200 kilometers), NOAA 16-DEB (altitude around 825 kilometers), Sentinel 6 (altitude around 1,300 kilometers), and the small satellite CUTE1.7 (20x20x10 cm; height around 600 kilometers).
Subsequently, GESTRA successfully completed the calibration campaign for entry into the European Space Surveillance and Tracking program (EU SST) and has been in initial operational service since mid-2024. Today, GESTRA delivers up to 13,000 tracks per day to the WRLageZ and, together with other sensors in Europe, contributes to the orbital catalog of the EU SST program.
Highly flexible and lightning-fast radar beam: Phased-array technology makes it possible
GESTRA was developed as a phased-array radar. The 256 individual antennas arranged on a circular, flat surface enable highly flexible and rapid Steering of the radar beam. The individual radiators are linked in such a way that the desired beam direction can be changed in real time. Furthermore, both antennas can be mechanically oriented in all axes. The data are collected and analyzed by a radar processor and transmitted to the WRLageZ in Uedem, where GESTRA is operated by the German Space Agency in DLR.
Networking and further performance enhancement
GESTRA currently consists of a transmit and a receive unit at the Schmidtenhöhe site in Koblenz. The German Space Agency in DLR and Fraunhofer FHR are jointly pursuing three projects to expand the GESTRA family. With GESTRA-EUSST and GESTRA-Networking, the resolution of the radar will be significantly increased. In the GESTRA-TX2 project, a second transmit unit is being developed, which will further boost the overall capability of the GESTRA system.