Space surveillance with GESTRA
The integration work and the testing of the individual subsystems are in full swing. In 2019, GESTRA (German Experimental Space Surveillance and Tracking Radar) will be transported to its final installation site in Koblenz, Germany, where it will be tested and calibrated as a complete system. In 2020, the system is to be handed over to the German Space Situational Awareness Center (GSSAC) in Uedem. On one hand, the GSSAC will then have a high-power radar sensor for space surveillance at its disposal. On the other hand, GESTRA promises to also provide other research institutes in Germany with valuable data for scientific use.
Integration and Monitoring of the Radar Infrastructure
Because of the high transmitting power, the partially mobile system will have a quasi-monostatic design. This means that the transmission and receiver systems will each be integrated into separate containers with dimensions of 18 x 4 x 4 m3. The integration of the subsystems into the containers was carried out in the order determined by the spatial conditions. First, the energy distribution cabinet was installed with all of its safety relays and high-current switches and then the heavy-duty scissors lift, the oil-free compressor, and the air conditioning system with its ventilation and suction pipework. This was followed by the installation of the energy supply units for the transmitting and receiving antennas and their integration into the control system. The installation of the cooling system into both containers was a highly complex integration process. The liquid cooling systems of the transmitting and the receiving unit consists of a primary cooling circuit with complex cold-water preparation and air back cooling as well as a secondary cooling circuit with a coordinated pump system to cool the antenna, the transmitting transformer, the radar processor, and the air conditioning. After all dedicated cooling and dehumidification units were integrated, the piping for these subsystems was installed. It was only possible to guarantee adequate spatial volume for the subsequent integration of the cable lines on the container ceilings for the subsystems' electrical power supply thanks to the detailed 3D system modelling of all devices and pipework. This multi-level line installation also ensures that the arrangement of the water and compressed air hoses is suitable for the transport.
The integration of the radar processor in the 3-rack format with a power loss of 45 kW and the built-in fire extinguishing possibility allows for the early analysis of the computing capacity to test the signal processing algorithms. After all of the mentioned subsystems were connected electrically, the next step was to implement and test all monitoring and sensor systems in these devices. Especially noteworthy here is the reliable air conditioning and dehumidification of the operating rooms to prevent condensate effects at low temperatures. The current constant monitoring of all operating states and environmental parameters of all integrated devices by means of an optimized monitoring program provides insights into the radar infrastructure's implemented product reliability. The antenna front end with the positioner will be installed in both containers in March 2019.
Currently, the integration work to set up the receiving model and then the receiving planks is underway. This will be followed by the equipment of the transmitting plank and the continuous antenna integration with all supply units. It should be emphasized here that the very complex, 130 cm long backplane circuit boards, which have been developed with a high manufacturing risk for supplying the planks, have been delivered and tested completely, thus being ready for installation.
In addition to the optimization of the radar's physical properties, GESTRA's detection capabilities are to be improved primarily by the signal integration based on as many pulses as possible. For this purpose, a model of the target signal will be parametrized for all relevant characterization values, before it undergoes an adapted signal processing in the value ranges to be expected for typical target objects in the low Earth orbit. The tracklet information will be derived from the subsequent threshold decision and the initiation of the orbit tracking of the object. This tracklet information will then be synthesized to a complete track by the Space Situational Awareness Center.
Remote Control of GESTRA
As a rule, GESTRA is designed to be operated remotely by the GSSAC, without on-site personnel. Accordingly, all components have been designed systematically for remote serviceability, including the possibility for a complete restart from a de-energized state. Security is guaranteed for this process: The encrypted end-to-end communication certified by the German Federal Office for Information Security (BSI) provides for tap-proof connections, while the three-network topology as well as the state-of-the-art firewall complete the overall concept.
To get to know the later operating procedures, a GESTRA command and data interface simulator based on the final network protocols was delivered to the future users in 2018 so that they can prepare their mission planning and analysis software parallel with the completion of the system hardware for the operation.