ADAPTIVE COSINE TRANSFORM CODING FOR COMPRESSION OF MARS-96 ELISMA INSTRUMENT DATA

Mars-96 ELISMA is a scientific project designed to measure the electri c and magnetic fields around Mars when the Russian spacecraft Mars-96 orbits the planet. The data rate of the on-board ELISMA instruments wi ll reach a figure which is about five times the telemetry-rate allocat ed to them. To overcome this problem, a coding was designed to compres s the data for the telemetry. This coding combines an adaptive cosine transform with marginal analysis. Data from the instruments are divide d into blocks with each block converted by the cosine transform into c oefficients. The marginal analysis method is performed on the coeffici ents to achieve a bit allocation vector specifying the level of the su bsequent Lloyd-Max quantization of the coefficients. This paper descri bes the coding algorithm and also shows simulation results for the com pression of geophysical data.