Hybrid SAR/ISAR ship target imaging using very long dwell spaceborne SAR. Preliminary results

Long dwell SAR modes, with the system staring at the same location for up to several tens of seconds, are well suited for the extraction of information concerning targets that are moving inside the observed scene. With reference to maritime surveillance applications, this paper presents preliminary results obtained exploiting spotlight extended dwell time images. In SAR imaging, moving targets typically exhibit motion-induced blurring, a phenomenon that is amplified in extended dwell time images, where the target may experience complex motion such as acceleration or rotation. To address this, a tailored sub-aperture processing chain that leverages hybrid SAR/ISAR techniques is introduced. The approach processes level-1 SAR images by segmenting the long dwell time into multiple shorter CPIs, yielding focused and scaled images of ship targets at different time instants. Additionally, an optimization technique is applied to select the optimal CPI and image time, ensuring the highest image quality and enabling the extraction of fine structural details of the ships. The effectiveness of the proposed method is validated using an ICEYE SAR image acquired over the Durban port area, with an extremely long dwell time of 25s.