Missions for NASA’s Discovery program lie outside the bounds of a decadal strategic plan, and so this report makes no recommendations on specific Discovery flight missions. The committee emphasizes, however, that the Discovery program has made important and fundamental contributions to planetary exploration and can continue to do so in the coming decade. 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 in fiscal year [FY] 2015). And so that the science community can plan Discovery missions effectively, the committee recommends a regular, predictable, and preferably rapid (.24-month) cadence for release of Discovery Announcements of Opportunity and for selection of missions.
An important small mission that lies outside the Discovery program is the proposed joint ESA-NASA Mars Trace Gas Orbiter that would launch in 2016. The committee supports flight of this mission as long as the currently negotiated division of responsibilities and costs with ESA is preserved.
The current cost cap for NASA’s competed New Frontiers missions, inflated to FY2015 dollars, is $1.05 billion, including launch vehicle costs. The committee recommends changing the New Frontiers cost cap to $1.0 billionFY2015, excluding launch vehicle costs. This change represents a modest increase in the effective cost cap and will allow a scientifically rich and diverse set of New Frontiers missions to be carried out, and will help protect the science content of the New Frontiers program against increases and volatility in launch vehicle costs.
Two New Frontiers missions have been selected by NASA to date, and a third selection was underway while this report was in preparation. The committee recommends that NASA select two additional New Frontiers missions in the decade 2013-2022. These are referred to here as New Frontiers Mission 4 and New Frontiers Mission 5.
New Frontiers Mission 4 should be selected from among the following five candidates:
• Comet Surface Sample Return,
• Lunar South Pole-Aitken Basin Sample Return,
• Saturn Probe,
• Trojan Tour and Rendezvous, and
• Venus In Situ Explorer.
No relative priorities are assigned to these five candidates; instead, the selection among them should be made on the basis of competitive peer review.
If the third New Frontiers mission selected by NASA addresses the goals of one of these mission candidates, the corresponding candidate should be removed from the above list of five, reducing to four the number from which NASA should make the New Frontiers Mission 4 selection.*
For the New Frontiers Mission 5 selection, the following missions should be added to the list of remaining candidates:
• Io Observer, and
• Lunar Geophysical Network.
Again, no relative priorities are assigned to any of these mission candidates.