Real time rotational motion compensation algorithm for focusing spot-SAR / ISAR images in case of variable rotation-rate

The problem of compensating image blurring induced by target rotation in Spot-SAMSAR imaging is investigated. Oppositely to what is generally assumed, the case of a variable rotation-rate during coherent processing time is considered since this usually happens in forward looking SAR geometry as well as in aircraft or ship ISAR imaging. A novel algorithm is proposed to solve the addressed problem with particular emphasis given to a possible mechanisation for real-time applications. To this respect, the performance in terms of required computational load is analysed. The concept of the proposed algorithm is derived by a suitable simplification of the SARllSAR signal phase equation. The effectiveness oftbe proposed algorithm is verified also by processing real radar data acquired during extensive flights campaign: the dramatic improvement, with respect to traditional techniques, demonstrates the effectiveness of the proposed approach.