Bottom Line: Finding 1: NASA is using analytical techniques, physical tests, and inspections to assess primary structures and functional systems, to the extent possible, and determine sparing needed to support safe functioning and full scientific utilization of the ISS through 2020. NASA is confident that it can execute necessary functioning and utilization; however, the supporting assessments for primary structures and functional systems are ongoing and all results are not yet available. Finding 2: NASA's assessment of the essential spares necessary to assure continued operations through 2020 appears to be supported by sufficient, accurate, and relevant underlying data. We found, however, that estimates of essential spares are sensitive to NASA's assumptions about ORU reliability.
