A baby step for China but a giant leap for humans: Three basic issues with Chinese initiative of moon-based earth observation SAR system

A Moon-based synthetic aperture radar (SAR) system can provide large-scale, long-term, and constant earth observation (EO). Nevertheless, several problems should be solved before implementation. The problems include the ultra-small range of antenna viewing angles, the largest cell size of SAR allowed without the consideration of range cell migration and the related antenna size, and the decorrelation caused by long integration time. Although the moon-based EO system is a concept at present, with a baby but concrete and persistent step, the giant leap for human beings will be achieved.