An empirical investigation of fault repairs and mitigations in space mission system software

Faults in software systems can have different characteristics. In an earlier paper, the anomaly reports for a number of JPL/NASA missions were analyzed and the underlying faults were classified as Bohrbugs, non-aging-related Mandelbugs, and aging-related bugs. In another paper the times to failure for each of these fault types were examined to identify trends within missions as well as across the missions. The results of those papers are now starting to provide guidance to improve the dependability of space mission software. Just as there are different types of faults, there are different kinds of mitigations of faults and failures. This paper analyzes the mitigations associated with each fault studied in our previous papers. We identify trends of mitigation type proportions within missions as well as from mission to mission. We also look for relationships between fault types and mitigation types. The results will be used to increase the reliability of space mission software.