We have developed a small SAR sensor, Micro X-SAR, compatible with 130 kg small satellite. It is capable of 3-meter resolution SAR image acquisition in strip-map mode and 1-meter resolution SAR image acquisition in sliding spotlight mode. This small SAR sensor was successfully demonstrated in orbit by a private company in 2021, Feb. This paper describes the next technical challenge of small SAR satellite with higher performance. We discuss on several types of SAR mission such as high resolution missions, wide swath missions, and constellation missions. Then we describe the present status of technical challenges to wideband, high power, and mass-productivity
