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

• Ensure that there are adequate levels of project funds for risk reduction and improved cost
estimation prior to final selection; and
• Develop a comprehensive, integrated strategy to control cost and schedule growth and enable
more frequent science opportunities.
SMALL MISSIONS
Within the category of small missions, there are three elements of particular interest: the
Discovery program, extended missions for ongoing projects, and “Missions of Opportunity”.
The Discovery Program
The Discovery program was initiated in 1992 as a way to assure frequent access to space for
planetary science investigations through competed PI-led missions. The low cost and short development
times of Discovery missions provide flexibility to address new scientific discoveries on a timescale
significantly less than 10 years. The Discovery program is therefore outside the bounds of a decadal
strategic plan, and this decadal survey makes no specific Discovery flight mission recommendations. The
committee stresses, however, that the Discovery program has made important and fundamental
contributions to planetary exploration, and can continue to do so in the coming decade. The
committee gives it its strong support.
Chapters 4-8 provide examples of the rich array of science that can be addressed with future
Discovery missions. At Mercury, orbital missions complementary to MESSENGER could characterize
high-latitude, radar-reflective volatile deposits, map the mineralogy of the surface, characterize the
atmosphere and the magnetosphere, and precisely determine the long-term rotational state. At Venus,
platforms including orbiters, balloons, and probes could be used to lower atmospheric chemistry and
dynamics, surface geochemistry and topography, and current and past surface and interior processes. The
proximity of the Moon makes it an ideal target for future Discovery missions, using both orbital and
landed platforms, building on the rich scientific findings of recent lunar missions, and the planned GRAIL
and LADEE missions.
Potential Discovery missions to Mars include a 1-node geophysical pathfinder station, a polar
science orbiter, a dual satellite atmospheric sounding and/or gravity mission, an atmospheric sample
collection and Earth-return mission, a Phobos/Deimos surface exploration mission, and an in situ aerial
mission to explore the region of the martian atmosphere not easily accessible from orbit or from the
surface. We note that NASA does not intend to continue the Mars Scout program beyond the MAVEN
mission, nor do we recommend that they do so. Instead, the committee recommends that NASA
continue to allow Discovery missions to be proposed to all planetary bodies, including Mars.
Primitive body investigations are ideally suited for Discovery missions. The vast number and
diversity of asteroids and comets provide opportunities to benefit from frequent launches. The proximity
of some targets allows missions that can be implemented within the context of the Discovery program.
Near the limit of the Discovery cost cap, it may be possible to collect and return samples from NEOs.
The diversity of targets means that proven technologies may be re-flown to new targets, reducing mission
risk and cost. And the population of scientifically compelling targets is not static, but is continually
increasing as a consequence of discoveries in the supporting research and analysis programs.
Because there is still so much compelling science that can be addressed by Discovery missions,
the committee recommends continuation of the Discovery program at its current level, adjusted for
inflation, with a cost cap per mission that is also adjusted for inflation from the current value (i.e.,
to about $500 million FY2015).
The committee does note that NASA has increased the size and number of external project
reviews for Discovery missions to the point that some reviews are counterproductive and disruptive. The
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