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

identified by the Outer Planet Flagship review panel. 74 Specific components highlighted as requiring
development include the following the following:
• In situ elements enabling extensive areal coverage. The Montgolfière balloon system
proposed for TSSM is a promising approach 50 , but an airplane, which could use an ASRG rather than an
MMRTG 52 , may be more appropriate if there is a limited supply of Pu-238;
• Mature in situ analytical chemistry systems that have high resolution and sensitivity; and
• Sampling systems that can operate reliably in cryogenic environments. (See Chapter 11 for
additional details.)
Furthermore, mission studies have shown that any future mission to Saturn will require the use of
suitable radioisotope power sources, thus placing a high priority on the completion of the ASRGs and the
restart of the plutonium production program within the U.S. Department of Energy.
The committee commissioned a detailed study of a Titan Lake Probe (Appendix D and G)
considering the mission and instrument capabilities needed to examine the lake-atmosphere interaction as
set forth in the TSSM study report 61 . In addition, the Titan Lake Probe study evaluated the feasibility and
value of additional capability to directly sample the subsurface and lake bottom. The integrated
floater/submersible concepts in this study were designed to make measurements at various lake depths
and even sample the sediment on the bottom of the lake. The findings indicated that such a system that
includes floater and submersible components and enhanced instrumentation would result in significantly
increased science, but also significantly increased mass relative to the simpler TSSM lake lander concept.
Based on results of this study, further studies are needed to refine lander concepts as part of a flagship
mission. Stand-alone lake lander concepts, independent of TSSM, were also studied (Appendix D and G)
but were judged to be less cost-effective than a lake lander integrated with TSSM.
FIGURE 8.13 The three elements of the 2009 TSSM mission architecture: A Titan orbiter, a lake lander,
and a hot-air balloon. SOURCE: ESA/NASA;
Enceladus Orbiter
Enceladus, with its remarkable active cryovolcanic activity, including plumes that deliver samples
from a potentially habitable subsurface environment, is a compelling target for future exploration, 75 and
OPAG recommended study of mid-sized Enceladus missions for the coming decade. 76 Mission studies
commissioned by the committee indicated that a focused Enceladus orbiter mission is both scientifically
compelling and at lower cost than Europa or Titan flagship missions (Appendix C). Enceladus orbiters
have been the subject of several previous mission studies, most recently in 2007. 77
The most important science goals for an Enceladus mission, in decreasing priority order, are the
following:
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