On board strip-based wavelet image coding for future space remote sensing missions

Abstract

Spacecraft sensor obtained data has to be stored on-board until an opportunity arises for it to be transmitted to the ground. 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, 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 and scientific missions, the authors propose a novel and efficient strip-based satellite image coder adapted for on board processing. The performances of their method are better than JPEG 2000 with a complexity lower than 60 operations per pixel. Furthermore, their method can be implemented for different image samplings. The authors quickly explain the general compression scheme used and the solution for on the fly DWT computation. They present the dynamic bit allocation and the regulation process chosen for rate control. Then, they evaluate the complexity and performances of their method comparatively to JPEG 2000.