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Algorithms and Tools

Figure 1: Examples of the Institute’s calibration ground equipment; left: corner reflector with 3 m leg length, middle: ground receiver for measuring transmit pulses, and right: transponder with adjustable RCS . Figure 2: Scenario used in the SARCON distributed target ambiguity analysis tool. The positions of the ambiguities are shown on plots of the iso-Doppler and iso-range lines

The core for our calibration and verification algorithms is the CALIX software, which is currently being upgraded for TerraSAR-X and ALOS. A key element of CALIX is the point target analysis tool featuring measurement of impulse response function parameters, integrated point target energy (for determination of absolute calibration factors), target/clutter ratios (to weight calibration factor estimates), as well as peak phase estimates in the case of multi-channel (e.g. quad-pol) data. Figure 1 shows a screen-shot of this tool. Furthermore CALIX offers tools for distributed target analysis and for geometric calibration (internal delay and data accuracy for accurately surveyed targets).

A contract from ESA/ESRIN was awarded for the development of the SAR product control software (SARCON) for ERS and ASAR products. Together with BAE Systems Ltd. as software engineering partner, SARCON has been extended and improved over the last years and is currently the standard software in ESRIN’s product control service. The limited ambiguity performance of ASAR in some beams was the driver for the development of a special distributed target ambiguity analysis tool that allows the estimation of ambiguity noise levels for a given scenario (see Figure 2).