About

Calibration Group of the Microwaves and Radar Institute

Calibration of synthetic aperture radar (SAR) systems is the main focus of this group and has been an important research field of the Microwaves and Radar Institute with almost 20 years experience. The primary task of SAR calibration is to estimate and compensate systematic errors of the complete SAR system, and to subsequently convert the image information into geophysical units. Once converted, maps of radar cross section (RCS) or backscattering coefficients in the case of standard SAR images can be created, or digital elevation models can be derived based on interferometric data acquisitions.

In recent years, SAR antenna technology has been extended from passive slotted waveguide arrays to active phased arrays, offering electronic beam steering capabilities required for acquisitions in different swath geometries and for operation in ScanSAR, Spotlight and TopSAR modes. Increasing complexity combined with the demand for high accuracy and a short duration for commissioning, these new SAR systems require likewise new calibration concepts. Innovative and efficient calibration concepts have been developed by the calibration group. These concepts have been established and applied for multiple modes high resolution SAR systems like TerraSAR-X, the first German satellite for commercial and scientific applications, and Sentinel-1, ESA's first contribution to the European Union's GMES (Global Monitoring for Environment and Security) program. Additionally, concepts for terrain height calibration of interferometric SAR systems like SRTM in 2000 or the current TanDEM-X mission have been developed.

To support the calibration activities, the calibration group has established and maintains and operates the DLR Calibration Facility (CALIF). CALIF comprises various calibration targets like corner reflectors, transponders, and ground receivers for L-, C- and X-band SAR systems. Thanks to the installed infrastructure the group is well prepared for the execution of calibration campaigns over large test sites, see the figure below.

Map of DLR Calibration Facility (CALIF)

The DLR Calibration Facility (CALIF), in the South of Germany, consists of 30 locations.

Calibration campaigns for the following missions have already been successfully carried out:

Currently the group is responsible for calibrating

  • TerraSAR-X (launched in 2007) and
  • TanDEM-X, which was launched three years later in June 2010.

Finally various software tools like CALIX or SARCON for analyzing and modeling a SAR system and for deriving the different calibration parameters have been developed and implemented; they can easily be adapted to future SAR missions.

Contact

German Aerospace Center (DLR)
Microwaves and Radar Institute
Satellite SAR Systems
Calibration Group
Dr. Marco Schwerdt

Oberpfaffenhofen
D-82234 We├čling
Germany

Tel.: +49 8153 28-3533
Fax: +49 8153 28-1449
Email: sar-...@dlr.de (Please click to reveal email address.)