Solutions with hertz

In the business unit Environment, the researchers at Fraunhofer FHR investigate the utilization possibilities of radar in the areas of renewable energies and environmental monitoring.


The energy revolution in Germany is slowly but continuously gaining momentum. Wind is set to be the backbone of the future power system and hence, new wind farms are popping up all over the country. But not everybody supports this way of generating green electricity, whether on-shore or off-shore. In the application phase, planners and operators have to prove that the planned wind farm is environmentally compatible. Radar can offer valuable help here.

The sensor operates independent of light and weather conditions; it works during the day and at night in rainy or foggy conditions. Objects can also be detected and identified with greater precision even over large distances. The sensor can be used for aircraft or also for birds. The blinking red lights on the wind turbines can be switched on and off as required and the rotor blades can be stopped when a flock of birds is approaching. Radar can be used to record what is happening on the inside and outside of a wind farm – the condition of the facility and already existing sensors can also be monitored.

The scientists face the challenge of detecting small objects at the maximum possible distance with the lowest level of power – sometimes also without transmit power. In such cases, the researchers use passive radar. Here, they use the signals from television stations or mobile phone masts and only evaluate the echoes.

No two customers are the same

Fraunhofer FHR carries out feasibility studies to examine the viability of a project that is commissioned by a customer. The institute accompanies its partners from the development of a system concept right up to the finished prototype. In addition to having the required theoretical know-how, the institute also has the ability to implement such systems in corresponding hardware. The researchers optimize their concept in complex models and simulations before commencing with the construction of the system. One distinguishing feature here is the fact that the scientists design the systems specifically for the task at hand as opposed to adapting ready-made devices to an application. At the same time, the scientists integrate the highest possible number of mass-market products so as to reduce costs to a minimum. They also develop specially adapted algorithms for signal processing – the core of each radar system.

Fraunhofer FHR has an extensive range of active as well as passive experimental systems and prototypes which are used to test new algorithms, techniques and components. Its network includes partners within and outside the Fraunhofer-Gesellschaft as well as industrial enterprises. The scientists are therefore also in a position to conduct tests outside of the laboratory under real-life conditions. Thanks to the combination of expertise and system competence, the customer is always provided with an optimal, tailor-made solution.

Spectral vision

Although radar can also be used to determine the ripeness of arable crops, more data than can be acquired with high frequency technology is needed for a holistic recording of the environmental parameters. At the Application Center for Multimodal and Airborne Sensing (AMLS), a cooperation between Fraunhofer FHR and the University of Koblenz, a group is currently conducting research on the fusion of radar and imaging sensors to facilitate an extensive examination of vegetation and the Earth's surface from the air. The application possibilities in this area also vary and range from the determination of the condition of agricultural and forested lands through measurement of the water quality up to the monitoring and documentation of nature conservation measures.

To this end, AMLS uses a specially adapted hyperspectral snapshot imager. The hyperspectral approach, which supplies a continuous wavelength spectrum in the visible and near-infrared range, is used for research purposes. Vegetation indices (e.g. the NDVI) are derived from spectral data – and not only from radar – to draw conclusions relating to the condition of the plants. The technique is currently being tested and further developed on vast areas of agricultural land in South Africa in cooperation with a partner. These results will form the basis for the development of an application-specific multispectral system, which specifically records and evaluates discrete, highly spatially resolved wavelengths.

A further airborne, dual-camera system for the thermal imaging of larger areas was also constructed this year and successfully tested. The system comprises a camera in the long-wave infrared range (LWIR) for the detection of emitted heat. This data is supplemented with spatial information from a the second high-resolution panchromatic camera. This second camera facilitates the precise georeferencing and mosaicking of the images. The system is used in the course of extensive flights along the Elbe. Further applications in the areas of agriculture, industrial plant as well as supply lines are currently being prepared.