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

MISSION STUDY PROCESS AND TECHNICAL EVALUATION
In the course of this decadal survey, the committee commissioned technical studies of many
candidate missions (Appendix G). These candidate missions were selected for study on the basis of white
papers submitted by the scientific community and the recommendations of the panels. Each study was
led by one or more “science advocates” from the committee’s panels (selected by the panel based upon
their expertise to represent the panel’s science interests), and was conducted by the Jet Propulsion
Laboratory, the Applied Physics Laboratory, Goddard Space Flight Center, or Marshall Space Flight
Center. The studies were funded by NASA and delivered to the agency, which then delivered them to the
decadal survey. Although NASA was aware of the contents of the studies, the agency was not involved in
the direction of the studies themselves or their prioritization by the decadal survey.
A subset of the mission studies was selected by the committee for further Cost and Technical
Evaluation (CATE) by The Aerospace Corporation, a contractor to the National Research Council. This
selection was made on the basis of the four prioritization criteria listed above. 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 estimate 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. It
therefore reflects cost impacts that may be beyond the control of project managers and principal
investigators. It includes a probabilistic model of cost growth due to technical and schedule risks, and
hence projects cost growth resulting from insufficient technical maturity identified as part of the technical
evaluation. Following NASA policy, costs were estimated at the 70 percent confidence level. Appendix
C discusses the CATE process in more detail.
The CATE process typically resulted in cost estimates that were significantly higher than the
estimates produced by the study teams. 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. In the sections below, we present both a recommended
plan that is based on these conservative cost estimates, and recommendations for what could be added to
the plan if the estimates prove to be too conservative.
It should be stressed that the studies carried out were of specific “point designs” for the mission
candidates that were identified by the committee’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. This fact is one of many
reasons why a cautious approach to cost estimation is appropriate. The sections below make specific
recommendations for steps that should be taken if the projected costs of certain missions grow beyond
expected bounds.
DEFINITION OF MISSION COST CLASSES
The committee’s statement of task divides NASA’s planetary missions into three distinct cost
classes: small missions costing less than $450 million current year dollars, medium missions costing
between $450 and $900 million, and large missions costing more than $900 million current year dollars.
The first corresponds to the Discovery and Mars Scout programs, the second to the New Frontiers
program, and the third to the so-called “Flagship” missions. It is within the committee’s purview, per the
statement of task, to recommend changes to the classes, including their cost ranges.
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