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

8. Determine the composition, structure, particle-size distribution, dynamical stability, and
evolutionary history of the rings, as well as the geology, geophysics, and surface composition of
small satellites.
9. Determine the vertical profile of zonal winds as a function of depth in the atmosphere, in
addition to the presence of clouds as a function of depth in the atmosphere.
New Frontiers Missions
The New Frontiers line is an essential component of NASA’s portfolio. Missions of this scope
can achieve highly focused goals that can be combined with results from flagship missions to
significantly advance scientific progress. However, the committee’s detailed mission studies revealed
that the current cost cap of New Frontiers precluded nearly all outer solar system exploration. One
exception was a Saturn Probe mission.
Saturn Probe
For a mission like the Saturn Probe, the current operating systems and protocols (extant
paradigms and likely risk/cost analyses) dictate that launching and operating an empty rocket (zero
payload) to fly past the Saturn system just barely fits within the 2009 New Frontiers cost cap. This is true
for any mission beyond Saturn as well: similar results surfaced for other New Frontiers mission concepts
to targets in the outer solar system. The Saturn Probe study was particularly illustrative because it was
stripped down to almost an empty rocket and yet was still substantially over $1 billion including launch
costs (the committee examined a single-probe mission design; multiple probes would further enhance the
science yield). For reference, an extremely capable payload is a small fraction of the cost of the rocket
(and thus the mission): Phase A-D costs of the probe, including aeroshell and payload, are only of order
10 percent of the total mission cost; the science payload itself is only of order 3 percent.
The prioritized science objectives for a Saturn Probe mission under an expanded New Frontiers
cost cap recommended in Chapter 9 are:
• Highest Priority Science Objectives
1. Determine the noble gas abundances and isotopic ratios of H, C, N, and O in Saturn’s
atmosphere.
2. Determine the atmospheric structure at the probe descent location acceleration.
• Lower Priority Science Objectives 104
3. Determine the vertical profile of zonal winds as a function of depth at the probe descent
location(s).
4. Determine the location, density, and composition of clouds as a function of depth in the
atmosphere.
5. Determine the variability of atmospheric structure and presence of clouds in two
locations.
6. Determine the vertical water abundance profile at the probe descent location(s).
7. Determine precision isotope measurements for light elements such as S, N, and O found
in simple atmospheric constituents.
The Saturn shallow probe targets very specific science goals. Retrieved elemental compositions
from Saturn can be combined with those from the Jupiter/Galileo probe to constrain solar system
formation models; in situ Saturn observations can leverage the results of remote sensing obtained with the
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