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Proceedings Fifth IEEE International Symposium on Requirements Engineering (2001)
Toronto, Canada
Aug. 27, 2001 to Aug. 31, 2001
ISBN: 0-7695-1125-2
pp: 0222
Robyn R. Lutz , Jet Propulsion Laboratory and Iowa State University
Ines Carmen Mikulski , Jet Propulsion Laboratory
Abstract: This paper reports the results of a small study of requirements changes to the onboard software of three spacecraft subsequent to launch. Only those requirement changes that resulted from post-launch anomalies (i.e., during operations) were of interest here, since the goal was to better understand the relationship between critical anomalies during operations and how safety-critical requirements evolve. The results of the study were surprising in that anomaly-driven, post-launch requirements changes were rarely due to previous requirements having been incorrect. Instead, changes involved new requirements (1) for the software to handle rare events or (2) for the software to compensate for hardware failures or limitations. The prevalence of new requirements as a result of post-launch anomalies suggests a need for increased requirements-engineering support of maintenance activities in these systems. The results also confirm both the difficulty and the benefits of pursuing requirements completeness, especially in terms of fault tolerance, during development of critical systems.

I. C. Mikulski and R. R. Lutz, "Evolution of Safety-Critical Requirements Post-Launch," Proceedings Fifth IEEE International Symposium on Requirements Engineering(RE), Toronto, Canada, 2001, pp. 0222.
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