A Space-Variant SAR Image Formation Algorithm for Eccentric Orbits Around Small Bodies

Abstract

This paper presents an image formation algorithm for the focusing of SAR data with space-variant impulse response functions caused by eccentric orbits around small high-curvature surfaces, such as is encountered in stable orbits around Saturn's moon Enceladus, a potential target for future SAR missions such as the Nightingale mission concept under development at JPL. Due to the extreme geometry, the range history shows a significant dependence on the target's azimuth position within time scales significantly shorter than the synthetic aperture duration. Therefore, additional steps are needed in order to compensate for this effect and minimize image degradation. In this context, the present contribution evaluates the space variance of the geometry for SAR surveys over Enceladus and proposes a processing flow to account for it. Point target simulations using the proposed processing algorithm are shown to verify the approach.