自主火星离子与中性粒子分析仪数据压缩算法设计

火星离子与中性粒子分析仪共设计10种在轨探测模式,不同探测模式下数据率不同,多种探测模式下数据量远超出最大下行数据率的限制。为降低数据率,利用仪器内部FPGA有限的资源对压缩处理方法进行了详细设计。通过分析仪器数据特点,火星离子与中性粒子分析仪压缩算法采用合并处理、对数压缩和无损压缩三种压缩算法组合。对于每种探测模式,FPGA程序可根据压缩标志选择相应压缩算法,实现三种压缩算法串行使用,或选择其中一种或两种算法。并且压缩标志可通过注入指令改写,实现在轨时根据需求灵活配置。合并处理压缩比为2或4,对数压缩的压缩比为2,无损压缩效率与样本数据间的相关性有关。在此基础上,利用等离子体定标测试系统完成了地面测试。测试结果表明,各探测模式下科学数据经过压缩后数据率满足任务指标要求。

Data Compression Algorithm of the Ion and Neutral Particle Analyzer for the First Chinese Mars Mission

An integrated ion and neutral particle analyzer is built for the first Chinese Mars exploration project, which has ten detecting modes. Most detecting modes of the analyzer produce data far more than data capability of the Mars project. A special data-processing method is presented, including data merging, logarithmic compression and lossless compression. By setting symbols in FPGA, all the three compression algorithms can be used serially, or only requisite algorithms are selected, making data-processing flexible. The compression ratio of data merging is 2 or 4, and logarithmic compression is 2. The compression ratio of lossless compression is necessarily related to data characteristic in different detecting mode. Furthermore, the experiment results show that the data-processing method has good performances and the data rate fulfills the requirements for the project.