gle event upset susceptibility were utilized in payload applications. Advances in technology has resulted in a profound increase in the single event susceptibility of devices, and the complexity of payload systems has significantly increased the number of opportunities for these effects to occur. Systems engineering consideration of single event effects, a methodology for assessing SEE criticality, the identification of requirements for mitigation and fault tolerance, and the capability to perform design validation and verification are essential to design for compatibility with the space radiation environment. An understanding of both the functional impact of single event induced errors and their probability or rate of occurrence is necessary to establish design requirements for mitigation or tolerance provisions. Functional analysis, including the capability to analyze the propagation of error conditions, may utilize flowchart-like methods such as functional flow diagrams to provide traceability in error propagation. Identification of the path from fault occurrence to system level effects enables both an understanding of the consequences of the fault and identifies the opportunities for the application of mitigation or fault tolerance techniques. Subsystem functions, and hence the consequences of single event effects which may compromise these functions, may be categorized with regard to the criticality which they represent to the system in meeting required operational specifications. Usually, three or four criticality classifications are established for use in representing the severity of consequences of single event effects. The classifications usually comprehend the degree to which system operation is affected, the frequency which such an effect may be expected to occur, and the duration which compromised system operation is expected to persist. The most benign classification may be termed non-critical, or error-functional. This includes those effects which present little adverse consequences, occur infrequen