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An Assessment of Space Shuttle Flight Software Development Processes
IV&V IN THE SHUTTLE PROGRAM
Details of the approach used by Intermetrics and Smith Advanced Technology to provide software IV&V, as well as the overall NASA approach to flight software V&V, are described in Appendix D and Appendix E, respectively. To summarize, NASA's current practice of software IV&V on the Shuttle program consists of a combination of a modified form of IV&V performed by Intermetrics and Smith Advanced Technology, along with an internal form used by the development contractors.
Each development contractor has a managerially-independent IV&V team that oversees the team that develops the software. For example, the IBM development team and internal IV&V team report to different organizations within the company. The development contractors perform a rigorous internal IV&V to assure that they are following their own established processes correctly and that the delivered product meets the given requirements.
The IV&V contractors, Intermetrics and Smith Advanced Technology, report to NASA at the same level as the development contractors. The IV &V effort by Intermetrics and Smith Advanced Technology is focused and product oriented. For example, Intermetrics concentrates on the ascent and descent phases of the software. Other parts are occasionally addressed, but only after the program identifies them as a pressing issue. In response to written questions from the Committee, the headquarters Safety and Mission Quality (S&MQ) Office described the IV&V process as follows:
IV&V is defined as a process whereby the products of the software development life cycle phases are independently reviewed, verified, and validated by an organization that is neither the developer nor the acquirer of the software. IV&V differs from V&V only in that it is performed by an independent organization. 2
The Safety, Reliability and Quality Assurance (SR&QA) Office at the Johnson Space Center (JSC) reports directly to the center director, not to the Shuttle program or the NASA headquarters S&MQ Office, and so it is managerially independent of the Shuttle program. However, the funds needed for the SR&QA Office to perform its IV&V related activities are obtained in part from the Shuttle Program Office (and the headquarters S&MQ Office) so it is not financially independent from the Shuttle Program Office.
A third level of independence, which is not used by NASA for the Shuttle program but which is sometimes used by the Air Force and Navy, would be provided by having the IV&V contractor report to a group completely outside the Shuttle program (e.g., the NASA headquarters S&MQ Office).
In addition, the Astronaut Office and various contractors and NASA organizations also participate in the evaluation of the process and the product it ultimately produces. Because of the complexity of the process, it is described separately in Chapter 3.
NASA headquarters Safety and Mission Quality Office (Code Q) letter of 13 January 1992: Clarification of NASA's Independent Verification and Validation (IV&V) Perspective.