Achieving ambitious science missions is our goal, but at the same time it is essential that the missions are thoroughly evaluated. In this respect it is important to ensure that the cost estimates of a mission are realistic, and that once a financial commitment is made the budget allocated will not be exceeded. The risks of a project must also be identified, and if possible mitigated or avoided by alternative solutions.

Cost estimates are particularly challenging in the early mission phases, when not all technical details have been analysed and no binding commitments have yet been taken by industry. On this basis, cost estimates performed during the assessment phase are based on models and past experience, requiring scrutiny and continuous validation and update.

Finally the programmatic aspects are important, as missions often have dependencies upon other projects, international collaborators, payload developers and launch operators.

All such aspects are considered during the assessment phase. Moreover, the experience gained by missions in development is also tracked, in order to learn for the future.