CNES Studies for On-Board Compression of High-Resolution Satellite Images

Future high resolution instruments planned by CNES for space remote sensing missions will lead to higher bit rates because of the increase in resolution and dynamic range. For example, the ground resolution improvement induces a data rate multiplied by 8 from SPOT4 to SPOT5 and by 28 to PLEIADES-HR. Lossy data compression with low complexity algorithms is then needed while compression ratio must considerably rise. New image compression algorithms have been used to increase their compression performance while complying with image quality requirements from the community of users and experts. Thus, DPCM algorithm used on-board SPOT4 was replaced by a DCT-based compressor onboard SPOT5. Recent compression algorithms such as PLEIADES-HR one use wavelet-transforms and bit-plane encoders. But future compressors will have to be more powerful to reach higher compression ratios. New transforms have been studied by CNES to exceed the DWT but other techniques as selective compression are required in order to obtain a significant performance gap. This chapter gives an overview of CNES past, present and future studies of on-board compression algorithms for high-resolution images.