The calibration of imaging radar systems is the main focus of this group and has been an important research field in the Institute for over 20 years. The essential task of calibrating a SAR system is to transform the image information into geophysical parameters like radar cross section maps or digital elevation models. The different error contributions of a SAR system have to be identified, estimated and finally corrected. Increasing complexity of new SAR systems combined with the demand for high accuracy and short duration of the commissioning phase require new calibration concepts. Only such concepts allow to calibrate multiple mode high resolution SAR systems like TerraSAR-X with reasonable effort.
The Calibration Group has been developing and operating the Calibration Facility Oberpfaffenhofen (CALIF), comprising various calibration targets like corner reflectors, transponders and ground receivers in L-, C- and X-band, and the required infrastructure for the preparation and execution of calibration campaigns over large test sites. Furthermore, various S/W tools for the analysis and modelling of a SAR system and for deriving calibration parameters have been developed and implemented and can be modified for future SAR systems. Successful preparation and execution of calibration campaigns has been demonstrated for a number of SAR missions: ERS-1/2 1991-1996, SIR-C/XSAR 1994, SRTM 2000, ENVISAT/ASAR 2002. Currently the group is responsible for the calibrating TerraSAR-X and started developing the interferometric height calibration concept for TanDEM-X.