Antenna model refinement technique from SAR data: A study on the ENVISAT ASAR instrument

A refinement technique of the antenna model considered to compute Synthetic Aperture Radar (SAR) data pattern is proposed in this work. The accurate knowledge of the antenna patterns of a SAR sensor is of main importance for precise SAR image processing. This requirement, coupled with tight needs for a short duration of the calibration process, have made necessary the investigation of innovative methods to calibrate complex SAR systems. When considering active arrays, the antenna patterns computed from homogeneous SAR data is often in disagreement with those obtained from a mathematical model (the antenna model). In this paper a correction factor is introduced within the antenna model, in order to overcome this discrepancy. This parameter is expressed as a corrected version of the matrix indicating the working status of the antenna. It is estimated through inversion by exploiting the patten information of SAR data, and it can be used for effective antenna model calibration. The effectiveness of the proposed method is assessed by considering ENVISAT ASAR rain forest-images.