Many types of data compression for SAR raw data have been developed during the past 30 years. Since most of them focus on reducing the number of bits required to store signal information onboard, the resulting complexity has been a great hindrance to the implementation of an efficient compression algorithm. We propose a new method of data compression that can be carried out onboard a small-sized platform. The method imposes no additional requirement on the antenna size by reducing the number of pulses needed to produce an image and compensating the missing pulses based on information provided from other pulses. The most complicated task of reconstructing the missing pulses can be performed in the ground station, not onboard the small platform. Because fewer pulses are needed, less power will be required for transmitting and receiving the pulses. This is advantageous for reducing the pulse repetition frequency (PRF), which normally becomes higher for smaller antennas. This method will be applied to our circularly polarized synthetic aperture radar (CP-SAR) system, which is currently being developed toward a mission onboard a microsatellite.