Abstract
The implementation of a viable Synthetic Aperture Radar (SAR) mission using small satellites faces significant technological and financial challenges, and this paper evaluates how small such a spacecraft could be made whilst still fulfilling a useful mission. SAR offers a range of complementary capabilities alongside other Earth Observation systems with various unique features, but developing such spacecraft has traditionally been expensive and technologically challenging. It is only in the most recent years that small satellite SAR missions have been implemented and operated, and this paper examines the state of the art and the challenges. Furthermore the opportunities of how small SAR satellites can help realise new Earth Observation capabilities not available on existing traditional SAR satellites are described using examples of missions under development or reference design missions.