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

The CATE team’s approach (Figure C.1) is based on the following principles:
• Use multiple methods and databases regarding past space systems so that no one model or
database biases the results. The CATE team used proprietary Aerospace models (e.g. Small Satellite Cost
Model) and space-industry standards (e.g. the NASA/Air Force Cost Model (NAFCOM)).
• Use analogy based estimating; tie costs and schedule estimates to NASA systems that have
already been built with known cost and schedule.
• Use both system level estimates as well as a build-up-to-system level by appropriately
summing subsystem data so as not to underestimate system cost and complexity.
• Use cross checking tools, such as Complexity Based Risk Assessment (CoBRA) to cross
check cost and schedule estimates for internal consistency and risk assessment.
• In an integrated fashion, quantify the total threats to costs from schedule growth, the costs of
maturing technology, and the threat to costs owing to mass growth resulting in the need for a larger, more
costly launch vehicle.
In summary, an analogy-based methodology ties the estimated costs of future systems to the
known cost of systems that have previously been built. In other words, it provides an independent
estimate of cost and complexity of new concepts anchored with respect to previously built hardware. The
use of multiple methods such as analogies and standard cost models ensures that no one model or
database biases the estimate. The use of system-level estimates and arriving at total estimated costs by
statistically summing the costs of all individual Work Breakdown Structure (WBS) elements ensures that
elements are not omitted and that the system-level complexity is properly represented in the cost estimate.
The assessments of technology, cost, and schedule are inextricably intertwined. However, it is
easier to describe each element of the overall assessment (e.g., technical, schedule, and cost) separately
noting in each instance the linkages to the overall CATE assessment.
Technical
The evaluation of technical risk and maturity in the CATE process focuses on the identification of
the most important technical risks to achieving the required mission performance and stated science
objectives. The assessment is limited to top-level technical maturity and risk discussions. Deviations
from the current state of the art as well as system complexity, operational complexity, and integration
concerns associated with the use of heritage components are identified. Technical maturity and the need
for specific technology development are evaluated by the CATE technical team including readiness levels
of key technologies and hardware. During the assessment of the technical risk areas and concept
maturity, the technical team interacted with the cost and schedule teams so that technical risks could be
translated into schedule and cost risk.
The CATE technical evaluation is limited to high level technical risks that potentially impact
schedule and cost. The CATE process places no cost cap on mission concepts and hence risk as a
function of cost is not considered. Concept maturity and technical risk are evaluated on the ability of a
concept to meet performance within launch dates proposed with adequate mass, power and performance
margins.
CATEs also evaluate proposed mass and power contingencies with respect to technical maturity.
If the CATE technical team concludes that these contingencies are insufficient, the contingencies are
increased based on historical data on mass and power growth. In some cases, growth in mass and power
requirements necessitate the use of larger launch vehicles to execute the scientific mission. The
assessments of required mass and power increases—and the potential needs for more capable launch
vehicles—are provided to the CATE cost and schedule experts for incorporation into their estimates.
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
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