Multi-look autofocus in high resolution inverse SAR imaging

Inverse synthetic aperture radar (ISAR) imaging is a technique for producing radar images of man-made targets. The relative motion between the target and the radar is the key point of the process. Autofocus motion compensation methods are commonly applied to form well focused images. But some major attributes of these images remain partially unknown. We have developed a method for estimating the relative distortions between successive images. We have applied this method to produce auto-registered multi-looks images. Results of this registration may be used for many other purposes. The method relies on the use of the RELAX algorithm for extracting the scatterers positions in each image and of a constrained minimization of a non-linear matching cost function according to a distortion model. It is applied to high resolution radar data of an aircraft and a satellite