External Calibration of Multi-Channel SAR Sensors Based on the Pulse-by-Pulse Analysis of Range Compressed Data

Abstract:
The paper describes a method for the accurate calibration of multi-channel SAR instruments, such as those required to support SAR polarimetry, single-pass interferometry and digital beam-forming, on the basis of dedicated SAR acquisitions containing reference targets with known properties. Unlike conventional approaches, the method is based entirely on the analysis of range-compressed raw data. It leverages the pulse-by-pulse analysis of amplitude, phase and delay variations observed within the range histories of reference targets to fully characterise and correct propagation direction dependent calibration issues. In addition, the approach does not require SAR image focussing in azimuth, which is essential in cases where azimuth focussing requires beam-forming techniques and thus presupposes an accurate calibration of the sensors’ antenna array. The paper illustrates and validates the proposed approach using real multi-channel SAR data acquired by DLR’s airborne F-SAR instrument.