Although the objective of the NMP technology validation missions is to enable future science missions, the NMP missions themselves are not science-driven. They are technology-driven, with the principal requirements coming from the needs of the advanced technologies that form the "payload." The missions are high risk because, by their nature, they incorporate unproven technologies that, in general, will not have functionally equivalent back-ups. (Indeed, if an advanced technology does not pose a high risk, flight validation by NMP is not required.)