We have developed and demonstrated in 2021 small SAR satellites of 1-m ground resolution with novel deployable slot array antennas. This paper newly proposes a novel concept of quasi-two-dimensional SAR satellites, SAR-DiskSats with this deployable passive slot array antenna. The deployable slot array antennas can be compactly folded in the quasi-two-dimensional satellite body. Also, it is possible to install flexible solar cell sheets on the back side of the antenna because the antennas do not dissipate heat. This quasi-two-dimensional satellite configuration is suitable to for stacking in a rocket faring for mega-constellation launching. Another advantage of the SAR-DiskSat is the possibility of VELEO (very low Earth orbit) operation. A thin edge cross-section makes aero drag small and there is an advantage of short range in terms of signal-to-noise ratio. This advantage of RF power makes it easier to improve its ground resolution. We are developing a new corporate feed slot array antenna with very wide-band (1.2-GHz bandwidth in X band) for 0.25-m ground resolution. The final goal of this SAR-DiskSat would be a mega- constellation of 0.25-m ground resolution in VLEO
