Multibaseline 3-D Circular SAR Imaging at L-band

Abstract:
Circular SAR has become of increased interest in the SAR community due to its potential of 3-D reconstruction and its capability of getting resolution of up to ~ λ/4 for isotropic targets. A single circular pass offers both, the best possible resolution in the horizontal plane and 3-D imaging. However, artifacts such as circles or arcs are present, when the assumed height during focussing is not that of the target. In 3-D imaging this artifacts are seen as cone-shaped sidelobes, due to the poor resolution in the direction perpendicular to the line of sight. In this work, a multibaseline fully polarimetric circular SAR campaign using DLR’s F-SAR system at L-band is presented. The purpose of this experiment is to enhance the resolution while focusing 3-D images by means of a sparse sampling in the kz space. An autofocus technique is implemented to correct residual aircraft motion errors. Processing methods such as Fast Factorized Back Projection for circular tracks and sparse imaging reconstruction for 3-D are used in this paper. Finally, the first demonstration of holographic SAR tomography of a forest area is presented.