Effects of the Earth’s Irregular Rotation on the Moon-Based Synthetic Aperture Radar Imaging

The Moon-based Synthetic Aperture Radar (SAR) offers an exceptionally wide spatial coverage and short revisit time for the Earth observation. However, the complex imaging geometry in Moon-based SAR-Earth's target motion, where both the Earth's rotation and lunar revolution exert, poses a great challenge in signal processing and image formation. The Earth's rotation, in particular, plays a dominant role in the aperture synthesis processing of the Moon-based SAR. However, the Earth's rotation, being irregular due to perturbations, induces coordinate drifts and leads to variations in the Moon-based SAR's Doppler parameters. As a result, the image formation of the Moon-based SAR is profoundly impacted by the Earth's irregular rotation. In this paper, we investigate Earth's irregular rotational effects on the imaging performance of the Moon-based SAR through a comprehensive analysis of the relative motion between a Moon-based SAR and Earth's target. Theoretical analyses and numerical simulations show that the effects of the Earth's irregular rotation affect the geometric fidelity and azimuth focusing of the Moon-based SAR; thus accentuating the necessity for special care of the Earth's irregular rotation in light of image focusing.