A Quantitative Approach to Performing Independent Schedule Estimates (ISE) Of Planetary and Earth-Orbiting Missions
Emmons, D.; Bitten, R.
The Aerospace Corporation

This paper examines a multi-level quantitative schedule analysis and estimating approach similar to one that is used when evaluating proposal costs, and cost risks. The Aerospace Corporation has developed a process for performing independent schedule estimates (ISE), which utilizes an analogy-based schedule assessment methodology, and permits greater insight into mission development times. Specific examples of how this tool has been used to evaluate overall development time and interim development milestone plans will be presented. Additionally, data will be shown for a past application of this tool in evaluating the schedule risk of a mission, and how it has been used to determine reasonable schedule reserves. Furthermore, the cost growth impacts of such specific schedule risks will be presented for a number of cases. Finally, a discussion of schedule confidence levels in setting schedule reserves will be discussed. The authors have used this tool in many proposal evaluations and independent assessments when estimating planetary and earth-orbiting mission schedules.