The problem diagnosis and resolution techniques applied to the primary on-board GN&C software developed for the NASA Space Shuttle

A systematic process for the timely diagnosis of user-reported problems involving the Space Shuttle primary on-board software is discussed. The Shuttle on-board software users and support approach are briefly described. The problem-diagnostic procedures described include fact finding, iterative problem resolution techniques, program cross reference, magnified timeline construction, cause and effect graphs, cyclic or multipass process evaluation, trap patches and traces, process desensitization, and common denominator determination. The subsequent process of problem resolution is then discussed.