Reliability prediction of a trajectory verification system

The existence of software faults in safety-critical systems is not tolerable. Goals of software reliability assessment are estimating the failure probability of the program, /spl theta/, and gaining statistical confidence that /spl theta/ is realistic. The paper presents practical problems and challenges encountered in an ongoing effort to assess and quantify software reliability of NASA's Day-of-Launch I-Loan Update (DOLILU II) system. DOLILU II system has been in operational use for several years. Bayesian framework is chosen for reliability assessment, because it allows incorporation of failure free executions, observed in the operational environment, into the reliability prediction.