Implementation aspects of a decompressor for compressed METEOSAT data on a VME/68000 system

Abstract

This report describes the results of a feasibility study into some aspects of a proposed METEOSAT image data compression unit. The study was performed to support the preparation of a proposal for ESOC. For the considered algorithms (ESTEC 1 & MEANDER 1) an estimate of the needed processing power based on the 68000 instruction set was made. This showed that a multiprocessor 68000 system would be capable of performing this task. For the estimate it was necessary to code part of the decompression algorithms. The coding of the algorithms has to be done in assembler to utilize the 68000 optimal and reach the required speed. The varying effective compression ratio of the considered algorithms and the limited output rate of the decompression require a buffer to store the incoming data. The required buffer size depends on the in- and output speed of the decompressor and the compression ratio of the incoming data. The required buffer is large but well within the reach of current available VME technology. Further the effect of channel errors on the design of the decompression and the format of the compressed data set were given some attention. The results of this study indicate that the construction of the proposed decompression unit using a dual processor VME/68000 system is possible