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

(and the subsequent elements of Mars Sample Return) should be deferred until a subsequent decade or
cancelled outright.
It is likely that a significant reduction in mission scope will be needed to keep the cost of MAX-C
below $2.5 billion. A key part of this reduction in scope is likely to be reducing landed mass and volume.
In particular, it is crucial to preserve, as much as possible, both the system structure and the individual
elements of MSL’s EDL system. A significant reduction in landed mass and volume can be expected to
lead to a significant reduction in the scientific capabilities of the vehicles delivered to the surface.
The committee recognizes that MAX-C is envisioned by NASA to be part of a joint NASA-ESA
program of Mars exploration that also includes the 2016 Mars Trace Gas Orbiter. In order to be of
benefit to NASA, this partnership must also involve ESA participation in other missions of the
three-mission Mars Sample Return campaign. It is therefore crucial to both parties for the partnership
to be preserved. The best way to maintain the partnership will be an equitable reduction in scope of both
the NASA and ESA objectives for the MAX-C/ExoMars mission, so that both parties still benefit from it.
The guiding principle for any descope process should be to preserve the highest priority science
objectives of the total Mars program for both agencies while reducing costs to acceptable levels.
The second highest priority Flagship mission for the decade 2013-2022 is JEO. However, its
cost as currently designed is so high that both a decrease in mission scope and an increase in
NASA’s planetary budget are necessary to make it affordable.
The Europa Geophysical Explorer, from which the JEO concept is derived, was the one Flagship
mission recommended in the previous planetary decadal survey. The scientific case for this mission was
compelling then, and it remains compelling now. Substantial technology work has been done on JEO over
the past decade, with the result that NASA is much more capable of accomplishing this mission than was
the case 10 years ago.
The difficulty in achieving JEO is its cost. The projected cost of the mission as currently
designed is $4.7 billion FY2015. If JEO were to be funded at this level within the currently projected
NASA planetary budget it would lead to an unacceptable programmatic imbalance, eliminating too many
other important missions. Therefore, while the committee recommends JEO as the second highest priority
Flagship mission, close behind MAX-C, it should fly in the decade 2013-2022 only if changes to both
the mission and the NASA planetary budget make it affordable without eliminating any other
recommended missions. These changes are likely to involve both a reduction in mission scope and a
formal budgetary new start for JEO that is accompanied by an increase in the NASA planetary budget.
It is clearly crucial to keep the budget increase required to enable JEO as small as possible.
Possible pathways to lower cost include use of a larger launch vehicle that would reduce cost risk by
shortening and simplifying the mission design, and a significant reduction in the science payload. NASA
should immediately undertake an effort to find major cost reductions for JEO, with the goal of
minimizing the size of the budget increase necessary to enable the mission.
The third highest priority Flagship mission is the Uranus Orbiter and Probe mission.
Galileo, Cassini, and Juno have performed or will perform spectacular in-depth investigations of Jupiter
and Saturn. The Kepler mission and microlensing surveys have shown that many exoplanets are ice-giant
sized. Exploration of the ice giants Uranus and Neptune is therefore the obvious and important next step
in the exploration of the giant planets.
The committee carefully investigated missions to both Uranus and Neptune. While both missions
have high scientific merit, the conclusion was that a Uranus mission is favored for the decade 2013-2022
for practical reasons. These reasons include the lack of optimal trajectories to Neptune in that time
period, long flight times incompatible with the use of Advanced Stirling Radioisotope Generators for
spacecraft power, the risks associated with aerocapture at Neptune, and the high cost of delivery to
Neptune. Because of its outstanding scientific potential and a projected cost that is well matched to its
anticipated science return, the Uranus Orbiter and Probe mission should be initiated in the decade
2013-2022 even if both MAX-C and JEO take place. But like those other two missions, the Uranus
Orbiter and Probe should be subjected to rigorous independent cost verification throughout its
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
S-10