Inverse synthetic aperture radar imaging: Air-to-air and air-to-surface examples

Imaging of mobile target from an airborne SAR (arguably called ISAR, because both sensor and target motions are involved in synthetic aperture) is customary for surface moving targets (trains and cars on ground, or large vessels on sea surface). Imaging of a flying aircraft is complicated by the more irregular and 3D relative motion due to target attitude fluctuations (similar issues occurs when imaging small vessels on strong sea condition because pitch and roll target motion are not dominated by the aspect angle changes due to sensor motion). Here are described the challenges of image formation and autofocus for air-to-air SAR imaging. Method is illustrated with some examples form the RAMSES SAR system.