NASA-HDBK-1002 (DRAFT-2), NASA TECHNICAL HANDBOOK: FAULT MANAGEMENT HANDBOOK (02-APR-2012)

NASA-HDBK-1002 (DRAFT-2), NASA TECHNICAL HANDBOOK: FAULT MANAGEMENT HANDBOOK (02-APR-2012)., This Handbook is published by the National Aeronautics and Space Administration (NASA) as a guidance document to provide guidelines and recommendations for defining, developing, analyzing, evaluating, testing, and operating the Fault Management (FM) element of flight systems. It establishes a process for developing FM throughout the lifecycle of a mission and provides a basis for moving the field toward a formal and consistent FM methodology to be applied on future programs. Fault Management (FM) is an engineering activity; it is the part of systems engineering (SE) focused on the detection of faults and accommodation for off-nominal behavior of a system, as well as a subsystem that has to be designed, developed, integrated, tested and operated. FM encompasses functions that enable an operational system to prevent, detect, isolate, diagnose, and respond to anomalous and failed conditions interfering with intended operations. From a methodological perspective, FM includes processes to analyze, specify, design, verify, and validate these functions. From a technological perspective, FM includes the hardware and control elements, often embodied in software and procedures, of an operational system by which the capability is realized and a situation awareness capability such as caution/warning functions to notify operators and crew of anomalous conditions, hazards, and automated responses. The goal of FM is the preservation of system assets, including crew, and of intended system functionality (via design or active control) in the presence of predicted or existing failures. FM demands a system-level perspective, as it is not merely a localized concern. A system’s design is not complete until potential failures are addressed, and comprehensive FM relies on the cooperative design and operation of separately deployed system elements (e.g., in the space systems domain: flight, ground, and operations deployments) to achieve overall reliability, availability, and safety objectives. Like all other system elements, FM is constrained by programmatic and operational resources. Thus, FM practitioners are challenged to identify, evaluate, and balance risks to these objectives against the cost of designing, developing, validating, deploying, and operating additional FM functionality. FM has emerged and developed along several paths in response to NASA’s mission needs (e.g., deep space vs. earth orbiters vs. human spaceflight) as reflected by the different approaches used in many organizations (e.g., JPL vs. GSFC vs. JSC), and by the ongoing activities to gain community consensus on the nomenclature. In fact, the term “fault management” is in itself something of a misnomer—the discipline of FM is concerned with failures in general and not just faults (which are failure causes rooted within the system as described in section 4). However, present use of the term “fault management” is synergistic with usage in the field of network management, where the International Organization for Standardization1 (ISO) defines FM as “the set of functions that detect, isolate, and correct malfunctions....” Likewise, the above-stated goal of FM (i.e., preservation of system assets and intended system functionality in the presence of failures) is consistent with the ISO-stated goal of having “a dependable/reliable system in the context of faults.”