Vision and Voyages for Planetary Science in the - Solar System ...

Mission Study Process and Technical Evaluation
In order to help develop recommendations, the committee commissioned technical studies of
many candidate missions. These candidate missions were selected for study on the basis of white papers
submitted by the scientific community (Appendix B provides a list of all white papers submitted).
A subset of the mission studies was selected by the committee for further analysis using the cost
appraisal and technical evaluation (CATE) process, which was performed by the Aerospace Corporation,
a contractor to the NRC. This selection was made on the basis of the four prioritization criteria listed
above, with science return per dollar being the most important. The CATE process was designed to
provide an independent assessment of the technical feasibility of the mission candidates, as well as to
produce a rough appraisal of their costs. The process takes into account many factors when evaluating a
mission’s potential costs, including the actual costs of analogous previous missions.
The CATE process typically resulted in cost estimates that were significantly higher than the
estimates produced by the teams that conducted the studies. The primary reason for this is that basing
cost estimates on the actual costs of analogous part projects avoids the inherent optimism of other cost
estimation processes. Only the independently generated cost estimates were used in evaluation of the
candidate missions by the committee in formulating the final recommendations. This approach is
intentionally cautious, and was designed to help avoid the unrealistic cost estimates and consequent
replanning that has sometimes characterized the planetary program in the past.
It should be stressed that the studies carried out were of specific “point designs” for the mission
candidates that were identified by the survey’s panels. These point designs are a “proof of concept” that
such a mission may be feasible, and provide a basis for developing a cost estimate for the purpose of the
decadal survey. The actual missions as flown may differ in their detailed designs and their final costs
from what was studied, but in order to maintain a balanced and orderly program, their final costs
must not be allowed to grow significantly beyond those estimated here.
Achieving a Balanced Program
In addition to maximizing science return per dollar, another important factor in formulating the
committee’s recommendations was achieving programmatic balance. The challenge is to assemble a
portfolio of missions that achieves a regular tempo of solar system exploration and a level of investigation
appropriate for each target object. For example, a program consisting of only Flagship missions once per
decade may result in long stretches of relatively little new data being generated, leading to a stagnant
community. Conversely, a portfolio of only Discovery-class missions would be incapable of addressing
important scientific challenges like in-depth exploration of the outer planets. NASA’s suite of planetary
missions for the decade 2013-2022 should consist of a balanced mix of Discovery, New Frontiers,
and Flagship missions, enabling both a steady stream of new discoveries and the capability to
address larger challenges like sample return missions and outer planet exploration. The program
recommended below was designed to achieve such a balance. In order to prevent the balance among
mission classes from becoming skewed, it is crucial that all missions, particularly the most costly ones, be
initiated with a good understanding of their probable costs. The CATE process was specifically designed
to address this issue by taking a realistic approach to cost estimation.
It is also important for there to be an appropriate balance among the many potential targets in the
solar system. Achieving this balance was one of the key factors that went into the recommendations for
medium and large missions presented below. The committee notes, however, that there should be no
entitlement in a publicly funded program of scientific exploration. Achieving balance must not be used as
an excuse for not making difficult but necessary choices.
The issues of balance across the solar system and balance among mission sizes are related. For
example, it is difficult to investigate targets in the outer solar system with small or even medium
missions. On the other hand, some targets are ideally suited to small missions. The committee’s
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