On Board Strip-based Wavelet Image Coding for Future Space Remote Sensing Missions

Why Image Compression in Space ? Images acquired on board spacecrafts (earth observation satellites, scientific probes...) represent in most cases very large volumes of data. It is then necessary to store these data on board (during non visilibility period) and to transmit them to ground. Due to the stringent limitations (in terms of mass, power and cost) which apply to on board equipements, it is essential to reduce to a minimum the on board storage capacity and the on board transmission rate needed to fulfill the mission. Compression algorithms used in space were based first on DPCM and then on DCT. Image quality evaluation determined however that for applications using the adaptive DCT, such as for SPOT 5 [1, 2], the maximum acceptable compression ratio was about 3 for high resolution observation and about 15 for scientific missions. Beyond that compression ratio, the occurrence of block effects in uniform areas and the loss of detail related to compression noise is no more acceptable for scientific use. To overcome these limits and to prepare future generations of Earth observation satellites [3, 4] and scientific missions, we propose a novel and efficient strip-based satellite image coder adapted for on board processing. The performances of our method are better than JPEG 20001 [5] with a complexity lower than 60 operations per pixel. Furthermore, our method can be implemented for different image samplings (dyadic, quincunx [6]...).