High-performance autofocusing for light-weight SAR platforms

Autofocusing is one of the key steps in the high-resolution SAR imaging. In the paper several important improvements to the recently developed local-quadratic map-drift autofocus are proposed. Important SAR image preprocessing steps applied before the local Doppler rate errors estimation are described. The weighting scheme for the evaluation of residual cross-track acceleration components is developed. It is illustrated that accounting of the local image contrast leads to better estimation precision. Also it is shown that the usage of measured real antenna orientation angles results in more reliable estimation of the local Doppler rate errors. Performance of the trajectory reconstruction technique is tested with experimental data obtained with X-band airborne SAR system.