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

2. U.S. participating investigator, where a co-investigator (non-hardware) is selected for a
science or technology experiment to be built and flown by an agency other than NASA;
3. New Science Investigations that propose a new scientific use of existing NASA spacecraft;
4. Small complete missions, where science or technology investigations can be realized within
the specified cost cap; and
5. Focused opportunities. That is, investigations that address a specific, NASA-identified flight
opportunity. This last SALMON vehicle was recently used to acquire the U.S.-provided instruments for
the Mars 2016 Trace Gas Orbiter.
In addition to their science return, Missions of Opportunity provide a chance for new entrants to
join the field, for technologies to be validated, and for future PIs to gain experience. The success of this
program will depend on a process that emphasizes flexibility and agility. The committee welcomes the
introduction of this highly flexible SALMON approach, and recommends that it be used wherever
possible to facilitate Mission of Opportunity collaborations.
Mars Trace Gas Orbiter
An important special case of a small mission is the proposed joint ESA/NASA Mars Trace Gas
Orbiter. A Mars orbiter to study the concentrations, temporal variations, sources, and sinks of
atmospheric trace gases, particularly methane, was identified in Chapter 6 to be of high scientific priority.
This mission is to be conducted jointly with the European Space Agency. The mission would launch in
2016, with NASA providing the launch vehicle, ESA providing the orbiter, and a joint science payload
that was recently selected. Based on its high science value and its relatively low cost to NASA, the
committee supports flight of the Mars Trace Gas Orbiter in 2016 as long as the division of
responsibilities with ESA outlined above is preserved. Holding to the 2016 launch schedule is
important, as failure to do so could significantly affect other missions, particularly to Mars, that are
recommended below. As discussed in greater detail below, the Mars Trace Gas Orbiter is intended
to be part of a long-term NASA-ESA collaboration on the exploration of Mars.
PRIORITIZED MEDIUM AND LARGE CLASS FLIGHT MISSIONS: 2013-2022
Optimum Balance across the Solar System
As described above, NASA’s program of planetary exploration should have an appropriate
balance among small, medium, and large missions. It is also important for there to be an appropriate
balance among the many potential targets in the solar system. Achieving this balance was one of the key
factors that went into the recommendations for medium and large missions presented below. The
committee notes, however, that there should be no entitlement in a publicly funded program of scientific
exploration. Achieving balance must not be used as an excuse for not making difficult but necessary
choices.
The issues of balance across the solar system and balance among mission sizes are related. For
example, it is difficult to investigate targets in the outer solar system with small or even medium
missions. On the other hand, some targets are ideally suited to small missions. The committee’s
recommendations below bear this fact in mind, and implicitly assume that Discovery missions will
address important questions that do not require medium or large missions in order to be addressed.
It is not appropriate to achieve balance simply by allocating certain numbers or certain sizes of
missions to certain classes of objects. Instead, the appropriate balance across the solar system must
be found by selecting the set of missions that best addresses the highest priorities among the
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
9-10