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

committee endorses the recommendation in a recent NRC report that NASA should reassess its approach
to external project reviews to ensure that: 9
• The value added by each review outweighs the cost (in time and resources) that it places on
projects;
• The number and size of reviews are appropriate given the size of the project; and
• Major reviews, such as preliminary design review and critical design review, occur only
when specified success criteria are likely to be met.
Program Tempo
Discovery Announcements of Opportunity (AOs)s were released in 1994, 1996, 1998, 2000,
2004, 2006 and 2010. The selected missions are listed in Table 9.2. Because Discovery missions are so
important for planetary exploration, and in order for the community to plan them effectively, the
committee recommends a regular, predictable, and preferably rapid (≤24 month) cadence for
Discovery AO releases and mission selections. Because so many important missions can be flown
within the current Discovery cost cap (adjusted for inflation), the committee views a steady tempo of
Discovery AOs and selections to be more important than increasing the cost cap, as long as launch vehicle
costs continue to be excluded.
The committee notes with some concern the increase in time between AO and launch in Table
9.1. Beginning with Lunar Prospector and continuing through Kepler, the time from selection to launch
for Discovery missions grew steadily from 4 to 9 years. (The expected launch of GRAIL in 2011 would
reverse this trend.) A hallmark of the Discovery program has been rapid and frequent mission
opportunities. The committee urges NASA to assess schedule risks carefully during mission selection,
and to plan program budgeting so as to maintain the original goals of the Discovery program.
Additional AO Opportunities
New knowledge regarding solar system objects has increasingly come from a combination of
ground- and space-based telescopic platforms. However, there is no explicitly defined program presently
in NASA planetary science where an orbital mission for observation of solar system objects can be
proposed. The Discovery Program Announcement of Opportunity (AO) issued in 2010 allows missions
to “target” any body in the solar system, save the Sun and Earth. But the AO is silent on the meaning of
the verb “target.” Based on presentations to the committee’s panels, it appears that a highly capable
planetary space telescope in Earth orbit could be accomplished as a Discovery mission. Such a mission
could be particularly valuable for observations of the giant planets and their satellites. The committee
recommends that future Discovery AOs allow space-based telescopes to be proposed, and that
planetary science from space-based telescopes be listed as one of the goals of the Discovery
program.
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
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