Future high resolution instruments planned by CNES for space remote sensing missions will lead to higher bit rates because of the increase in both resolution and dynamic range (bits per pixel), not compensated by the reduced swath. Data compression is then needed, with compression ratio goals always higher and with remaining unnoticeable artifacts. Moreover, space-borne earth observation instruments have several spectral channels (one panchromatic band and several spectral bands) which are generally processed independently, the spectral correlation being ignored. However, for optimum compression performance, algorithms must exploit both spectral and spatial correlation; such algorithms are called "multispectral". This paper proposes a low complexity and flexible fixed data rate compression algorithm for multispectral imagery specifically targeted for high-rate instruments used onboard of spacecraft.