The Institute contributes with its know-how and expertise in passive and active microwaves to the development and advancement of ground-based, airborne and spaceborne sensors, concentrating its research work on the concept and development of new microwave techniques and systems, as well as sensor-specific applications. The Institute‘s strength is the execution of long-term research programmes with applications in remote sensing, aeronautics, traffic monitoring and last but not least reconnaissance and security. In line with the German space programme, the Institute works in close collaboration with the German space agency, ESA, German industry, and the responsible ministries. Education of young scientists in the form of internships and diploma or doctoral theses is also an important part of the Institute’s mission.
Looking ahead to the next five years, the Institute will continue to initiate new projects and develop new techniques and technologies that are decisive for its long-term strategy. Examples from the present are the projects TerraSAR-X, TanDEM-X, SAR-Lupe as well as the demonstrator for future imaging reconnaissance systems, the new airborne SAR system – F-SAR, ALOS/PALSAR, MAPSAR, TRAMRAD, Sentinel-1, HABITAT and others. These projects are accompanied by research programmes that allow the Institute to keep a step ahead in the development of new research fields. Examples of research programmes are bistatic and multistatic SAR systems, digital beamforming (HRWS), inverse SAR, polarimetric SAR interferometry and tomography, calibration, signatures, propagation, antennas, and imaging techniques for radiometry and security.
Currently, the most important projects for the Institute are TerraSAR-X, TanDEM-X, SAR-Lupe and F-SAR (see description of the departments for more details).
SAR Center of Excellence
In 2000, following a peer review by an external board of examiners, the Microwaves and Radar Institute (HR) was recognised as a DLR Center of Excellence for SAR, due to its expertise in SAR technology, techniques, and missions. The German Remote Sensing Data Center (DFD) and the Remote Sensing Technology Institute (IMF) are partners of the Institute in this recognition. We collaborate closely with these institutes in the TerraSAR-X and TanDEM-X projects.
With the continuity of successful work in SAR over 25 years it has been possible to channel the experience gained from the planning and implementation of international space missions into a national SAR programme. Due to the end-to-end system know-how from data acquisition (including the Institute’s airborne SAR) to data interpretation and research into new applications, the SAR Center of Excellence has become one of the leading international research facilities in SAR. The aim of the work is to develop new SAR systems for the provision of multi-frequency, polarimetric and interferometric radar data, as well as to develop new algorithms for deriving geo/bio-physical parameters. The most important missions and projects with participation of the SAR Center of Excellenceare ERS-1, SIR-C/X-SAR, ENVISAT/ASAR and SRTM.
The institutes involved in the SAR Center of Excellence are complementary to each other in that they cover all sectors, from sensor technology and mission specification right through to high-accuracy operational processing and the value-added user products. Currently the SAR Center of Excellence is concentrated on the development work for TerraSAR-X. Together with the GSOC ( German Space Operation Center) the involved institutes are building and operating the TerraSAR-X ground segment, which is required for planning the mission, controlling the satellite and the instrument, processing of the radar data, as well as for archiving the received data and distributing them to the users. The work sharing in the ground segment for TerraSAR-X is as follows:
Holding the ground segment project leadership and the Principal Investigator position as well as the coordination of the science activities, the Institute is now starting the TanDEM-X phase B/C/D. The launch is planned for spring 2009. TanDEM-X represents the initial step towards a constellation of radar satellites and will help maintain Germany’s leading role in the sector of SAR technology in the X-band. The Institute aims with a successful realisation of TerraSAR-X and TanDEM-X to keep its recognition as a DLR SAR Center of Excellence.
In 2001, a new organisation with 4 departments was established in the Institute to focus the activities and expertise in each department. This was necessary due to the rapid increase of projects and external contracts in the Institute in 2002 and following years. In total, the Institute has 97 employees, including scientists, engineers, technicians and support personnel. In addition, approx. 20 guest scientists, diploma students and internship students are hosted by the Institute every year for a stay between 3 and 12 months.
Organization of the Microwaves and Radar Institute
The main projects of the Institute are related to spaceborne SAR systems. As far as civil spaceborne SAR projects are concerned, the activities are mainly carried out in the Spaceborne SAR Systems and Microwave Systems departments. New sensor concepts and techniques for future missions are also developed in these departments. The SAR Technology department contributes to the spaceborne SAR projects with airborne campaigns to simulate in advance the data products, to validate and cross-calibrate the satellite data and to demonstrate new techniques. The SAR Technology department also contributes with the development of new sensor-related applications. For military spaceborne SAR activities, all major projects and activities are performed in the Reconnaissance and Security department. The Institute’s expertise in passive microwave systems is also concentrated in this department, as most of the passive microwaves projects are related to security applications. The table below show the Institute’s departments and their respective research fields.
In a changing world, high resolution and timely geospatial information with global access and coverage becomes increasingly important. Constellations of SAR satellites, for example, will play a major role in this task, since SAR is the only spaceborne sensor that has all-weather, day-and-night, high resolution imaging capability. Examples of applications for such a constellation are environmental remote sensing, road traffic, hazard and disaster monitoring, as well as reconnaissance and security related applications.
One challenge for future spaceborne SAR systems is to optimise the performance/cost ratio so that constellations of SAR satellites become more affordable. Innovative concepts with bistatic and multistatic system configurations represent an attractive solution that exploits the use of small receiver satellites acquiring the backscattered signal of active MEO or GEO radar satellites (see fig. 2). Utilisation of the same transmit signal for different applications can also be explored, as demonstrated by GPS reflectrometry for ocean and land remote sensing. Digital beamforming on transmit and/or receive will solve the antenna size constraint in traditional systems that prohibits SAR sensors from achieving high azimuth resolution and a large swath width simultaneously. Digital beamforming is a clear trend for future systems, allowing great flexibility in sensor imaging modes, sensor calibration, interference removal and ambiguity suppression. These concepts will allow the implementation of a flexible SAR sensor network with a faster access time and almost continuous imaging capability, required for time critical applications. High flying platforms and unmanned vehicles will certainly act as a complementary platform for this network of sensors. Furthermore, radar satellites flying in close formation will allow the construction of sparse arrays with enhanced imaging capabilities.
Another important aspect for present and future microwave sensors is the ability to provide quantitative and reliable data to the user community. Today, the sensor information becomes multidimensional as different sensor sources, polarisations, temporal and spatial baselines, aspect angles and frequencies are used for parameter retrieval. The Institute will direct its efforts to more accurate system calibration to improve product quality and reliability as well as to the development of algorithms for sensor-specific parameter retrieval, as in the case of multibaseline polarimetric SAR interferometry. Besides SAR systems, the Institute also aims to increase its participation in the design and development of future spaceborne microwave systems such as range-Doppler and interferometric altimeters, radar sounders and advanced radiometers.
The vision of a SAR sensor network is in some respect not too far away. The Institute is committed to increasing its role in the development of future microwave satellites for remote sensing, reconnaissance and traffic monitoring. It aims to expand its expertise and leadership in strategically important projects and research areas. Together with its cooperation partners in DLR, industry and science the Institute will play a key role in the realisation of this vision.