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A Lossless Compression Algorithm Based on Differential and Canonical Huffman Encoding for Spaceborne Magnetic Data

Lossless compression for spaceborne magnetic data is significant, especially for small, low-cost satellites or deep space exploration spacecrafts. However, most of existing lossless compression algorithms are difficult to adapt to the embedded platform or the existing embedded algorithms have low compression ratio. In light of this, taking full advantage of the characteristics that the spaceborne magnetic data change slowly in a short time, a lossless compression algorithm based on differential encoding and canonical Huffman encoding is proposed. The original magnetic values are replaced with differential values with variable byte length to shorter the length of raw data. Canonical Huffman encoding can be performed twice after differential operation to further improve the compression ratio if the memory is sufficient. Experiments are carried out on spaceborne magnetic data of a satellite on an onboard computer. This algorithm can get compression ratio of 1.76 and 1.83 with canonical Huffman encoding disabled and enabled respectively, and the results demonstrate the superiority of the proposed algorithm in comparison with embedded LZW algorithms.