Criteria for range migration handling and azimuth multilooking in ScanSAR schemes. Applications to EnviSat/ASAR, RadarSat and SIR-C

We deal with two major questions of a ScanSAR processing: is it necessary or not to take into account the range migration, and how many looks in azimuth are necessary to have an optimal design? Starting from phase considerations, we obtain a criterion for the decision to take or not the range migration into account. From typical parameters of EnviSat/ASAR, RadarSat and SIR-C, we prove that the range migration is only absolutely necessary in the alternating polarization mode of EnviSat/ASAR and in the “fine resolution” mode of RadarSat. Range migration handling is recommended with SIR-C data. We also approach the important question of the optimal number of azimuth looks in a ScanSAR processing. With the help of two different criteria (a resolution criterion and a geometrical criterion), we derive the most appropriate number of looks for each ScanSAR scheme of EnviSat/ASAR, RadarSat and SIR-C. Finally, an efficient merging technique for the azimuthal multilooking is discussed