Security in Space
Fraunhofer FHR is one of the leading research institutes in the area of space reconnaissance. Space agencies from all over the world rely on the competence of the institute.
Modern society is becoming increasingly dependent on space-based infrastructures, i.e. services that are provided via satellite. These include television, communication and navigation. To protect these services with suitable measures, satellite operators need precise knowledge about space situational awareness, e.g. information relating to the type and number of objects and their orbits around the Earth.
The scientists at Fraunhofer FHR have been researching near-Earth space for over thirty years. Their work focuses on the development of technologies, processes and algorithms so that radar can be used to gather as much data as possible on space objects – from active satellites to space debris. Radar is the most suitable sensor for this task as the observation conditions are quite unfavorable: radar can be used by day and night, it produces distance-independent, high-resolution images and can also detect objects traveling at high speeds.
Nevertheless, the scientific documentation of space situational awareness is very challenging. Objects in orbit fly around our planet at speeds of over 28,500 km/h with the result that a particle just one centimeter in size could prove fatal for a satellite. In addition to the 20,000 known and catalogued objects, there are countless that have not yet been discovered. Only statistical values are available for the distribution of particles measuring one centimeter or less. As a result, only global risk assessments are possible. Individual collision forecasts are not feasible. Satellite operators, space agencies and scientists are, however, looking for solutions to make this possible. The central issue here is: how can good sensor data be acquired for small but highly dangerous particles?
Census for space debris
Scientists gather such data within the framework of beampark campaigns. These campaigns are conducted regularly with national and international partners. This type of experiment involves the combination of two systems: one serves as a transmitter (»illuminator«), the other as a receiver. The sensor group observes a section of the sky for a period of 24 hours. In this way, the scientists can detect objects just one centimeter in size. This is a record, at least in Europe.
Surveillance campaigns of a limited duration will, however, soon no longer suffice to guarantee traffic safety in near-Earth orbit. Providers, and in particular communication providers, are planning to use swarms of small and micro-satellites to bring mobile telephony and Internet which has been deployed in LEO (Low Earth Orbit, up to 2,000 km high) to the remotest corners of the Earth. The first satellite swarms have already been planned.
A new type of radar that is capable of seamless and continuous space surveillance is needed: phased arrays, i.e. electronically controlled array antennas, can conduct large-scale space surveillance around the clock. Using electronic beamforming, they can change their line of vision in a fraction of a second. Fraunhofer FHR is currently developing such a system, namely the »German Experimental Space Surveillance and Tracking Radar« (GESTRA) for the aerospace management of the German Aerospace Center (DLR).
Highest resolution also at 10,000 km
Fraunhofer FHR already proved its ability to develop such a system with the construction of a receiver prototype for ESA back in 2012. The system has surpassed expectations in all tests that have been carried out to date. Fraunhofer FHR's decades of experience played a major role here: in addition to the ability to design the hardware needed for such a system, the institute also has expertise in the programming of software for radar operation control. The development of complex algorithms for best possible processing of the signals from the received radar data is a further core competency.
The institute's space observation radar TIRA, the capabilities of which are unique throughout Europe, has been in operation for more than 40 years. The radar images generated with the space observation radar are sought by satellite operators and space agencies worldwide due to their richness in detail. In addition to the reconnaissance of orbital data for the purpose of collision prevention and re-entry forecasts, the scientists also focus on the identification and analysis of satellites: Which equipment is on board? Which tasks can the satellite perform? Is it active or passive? Is it stable or possibly out of control? Is it damaged? If yes, what is damaged and how was the damage caused? TIRA is also a valuable source of information during the launching phase. The partners are keen to know if the satellite is on the correct orbital path and if it was commissioned correctly. Safe operation is only possible when all solar panels and communication antennas have been fully extended. The researchers at Fraunhofer FHR can acquire this information from the radar images that have been generated. In this way, the partners can quickly be provided with valuable information for the further course of the mission.