Diagnostic models provide significant analytical and operational benefits to improve the dependability and efficiency of NASA systems.

The Constellation Program and the Exploration Technology Development Program (ETDP) funded the development of diagnostic models using the TEAMS (Testability Engineering and Maintenance System) tool for the Ares, Orion, and Ground Operations Projects to demonstrate operational uses for ground processing and launch operations. These models were found useful not only for operational pre-launch checkout, but also for analysis of failure effects, failure detection coverage, and fault isolation effectiveness. TEAMS, a commercial model-based tool from Qualtech Systems, Inc. (East Hartford, CT), performs fault diagnostics (isolation and identification). Fault isolation means identifying the location of the fault (cause) that is compromising system functions. Fault identification means identifying the failure mode (mechanism) that is causing system failure. Diagnostics refers to both fault isolation and identification functions.