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

with two. Hence, 15 ASRGs and five MMRTGs are implied by the recommended decadal survey plan
presented above; the cost-constrained plan would require only 15 ASRGs.
The recommended program cannot be carried out without new plutonium-238 production or
completed deliveries from Russia. The cost-constrained program could be, but only if ASRGs work as
currently envisioned and are certified for flight in a timely fashion. Moreover, unless additional
plutonium-238 is acquired, there will be only three ASRGs available for the subsequent decade, so there
will not be a Europa mission, a Titan Saturn System Mission, a mission to Neptune, or long-lived mission
to the surface of Venus in future decades. There are no technical alternatives to plutonium-238, and the
longer the restart of production is delayed, the more it will cost.
As noted above, the largest projected user of plutonium-238 in the recommended program is JEO.
Because the use of MMRTGs on JEO would consume so much of this valuable resource, the committee
recommends that JEO use ASRGs for power production. The duration of JEO is compatible with
ASRG use, and this change would alleviate (though not solve) the immediate plutonium-238 crisis. In
addition, because ASRGs are so broadly important to the future of planetary exploration, the committee
recommends that the remaining ASRG development and maturation process receive the same priority and
attention as a flight project.
All findings in the recent NRC report on RPSs remain valid. 16 With the one exception of NASA
issuing annual letters to the DOE defining the future demand for plutonium-238, none of the
recommendations of that report have been adopted. A decision to wait to a “better time” to fund activities
required to restart domestic plutonium production is just a different way of ending the program,
eliminating future science missions dependent on this technology for implementation.
The committee is alarmed at the status of plutonium-238 availability for planetary
exploration. Without a restart of plutonium-238 production, it will be impossible for the United
States, or any other country, to conduct certain important types of planetary missions after this
decade.
OPPORTUNITIES FOR INTRA-AGENCY, INTERAGENCY,
AND INTERNATIONAL COLLABORATION
There are three main areas in which collaboration with other parts of NASA could benefit the
solar system exploration program. First, as noted above, block buys of launch vehicles across NASA
have the potential to lower launch costs significantly. Second, astronomical telescopes, both groundbased
and space-based, can be used to observe solar system targets. The Hubble Space Telescope has a
long history of successful planetary observations, and this collaboration can be a model for future
telescopes such as the James Webb Space Telescope.
A third area of possible intra-agency collaboration is with NASA’s Exploration Systems Mission
Directorate (ESMD). NASA’s plans for future human exploration of the solar system currently include
ESMD-funded robotic precursor missions to the Moon, Mars, and asteroids. Because their focus is
preparing for human exploration, rather than science, these are not substitutes for any of the missions
recommended above, nor for Discovery missions. And, while they present opportunities for
collaboration, NASA’s Planetary Science Division should be cautious about imposing mission-defining
requirements, as we noted in Chapter 2. At the start of mission formulation, ESMD should inform the
science division what mission resources, if any, they are willing to allocate. Then, given a negotiated
agreement between ESMD and SMD, NASA should offer opportunities for scientists to propose
investigations on such missions by issuing Announcements of Opportunity in a manner similar to that for
participating on international missions or as was done for LRO.
Because ESMD robotic precursor missions target planetary bodies, they offer particularly good
opportunities for launch cost reduction via co-manifesting.
The greatest potential for interagency collaboration is also launch vehicle block buys and comanifesting,
reducing costs for all partner agencies. It will also be important for NASA to form a strong
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