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Sun-Solar System Connection

The Sun-Solar System Connection roadmap is a well thought out document that succeeds in placing many Sun-solar system science objectives into the context of the vision for space exploration.1 The roadmap correctly notes that the Sun-solar system science program has reached a level of maturity such that the focus has become “systems science” that addresses the strong interactions between all of the different components of the Sun-solar system environments such as the Sun, interplanetary medium, near-Earth and near-planet space environments, upper atmospheres, and heliosphere, even while essential work continues on the individual constituents. Such a systems approach was already required in the preexploration visions era to address Living with a Star and other near-Earth space environment studies, and it is also now needed to address the issues of developing and protecting exploration infrastructure and astronauts.2 The roadmap has made adjustments to accommodate resources and to support the exploration schedule; however the resulting overall priorities are roughly consistent with the key Sun-solar system-related NRC decadal survey The Sun to the Earthand Beyond.3 This outcome was anticipated with a follow-on NRC study, which reexamined the NRC decadal recommendations in the context of the exploration objectives.4

At the highest level the panel generally supports the science and implementation program developed in the roadmap. However, the roadmap suggests that the rationale depends much more strongly than necessary on a utilitarian requirements flowdown and “system science,” and thus it could be construed as undervaluing the role of fundamental discovery science. The panel identifies gaps that result from such a strictly utilitarian flowdown, suggests greater consideration of partnerships that can help fill gaps, and identifies shortcomings in the consideration of infrastructure maintenance. Although the panel understands that the roadmap document itself will not be updated according to recommendations given here, the panel does offer recommendations as to how the Sun-solar system science program should be articulated and organized in future NASA promulgations and planning activities, including the upcoming exercise to integrate the different NASA science discipline roadmaps.

INTRINSIC MERIT OF THE SUN-SOLAR SYSTEM CONNECTION ROADMAP SCIENCE PROGRAM

The NRC decadal survey in solar and space physics declares that the study of solar and space physics is “motivated by the deep-seated human impulse to know and understand the workings of Nature.”5 The impact of the study of these “workings of Nature” is leveraged dramatically by the extent to which the findings affect other disciplines and ventures. Specifically, the survey report and others go on to emphasize the importance of these investigations for understanding all solar system bodies, including our Earth, as well as astrophysical objects lying well beyond the reach of the Sun’s influence, where the same physics arises but is not directly observable, and the impact of such investigations on the study of the formation of solar systems and planetary systems, as well as the habitability of planetary systems.6,7 These reports point out that the fundamental physics of many important processes with wide application to laboratory and astrophysical plasma systems, for example, magnetic reconnection, are best addressed in the naturally occurring plasma environments available in the Sun-solar system domain.



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Review of Goals and Plans for NASA’s Space and Earth Sciences 6 Sun-Solar System Connection The Sun-Solar System Connection roadmap is a well thought out document that succeeds in placing many Sun-solar system science objectives into the context of the vision for space exploration.1 The roadmap correctly notes that the Sun-solar system science program has reached a level of maturity such that the focus has become “systems science” that addresses the strong interactions between all of the different components of the Sun-solar system environments such as the Sun, interplanetary medium, near-Earth and near-planet space environments, upper atmospheres, and heliosphere, even while essential work continues on the individual constituents. Such a systems approach was already required in the preexploration visions era to address Living with a Star and other near-Earth space environment studies, and it is also now needed to address the issues of developing and protecting exploration infrastructure and astronauts.2 The roadmap has made adjustments to accommodate resources and to support the exploration schedule; however the resulting overall priorities are roughly consistent with the key Sun-solar system-related NRC decadal survey The Sun to the Earthand Beyond.3 This outcome was anticipated with a follow-on NRC study, which reexamined the NRC decadal recommendations in the context of the exploration objectives.4 At the highest level the panel generally supports the science and implementation program developed in the roadmap. However, the roadmap suggests that the rationale depends much more strongly than necessary on a utilitarian requirements flowdown and “system science,” and thus it could be construed as undervaluing the role of fundamental discovery science. The panel identifies gaps that result from such a strictly utilitarian flowdown, suggests greater consideration of partnerships that can help fill gaps, and identifies shortcomings in the consideration of infrastructure maintenance. Although the panel understands that the roadmap document itself will not be updated according to recommendations given here, the panel does offer recommendations as to how the Sun-solar system science program should be articulated and organized in future NASA promulgations and planning activities, including the upcoming exercise to integrate the different NASA science discipline roadmaps. INTRINSIC MERIT OF THE SUN-SOLAR SYSTEM CONNECTION ROADMAP SCIENCE PROGRAM The NRC decadal survey in solar and space physics declares that the study of solar and space physics is “motivated by the deep-seated human impulse to know and understand the workings of Nature.”5 The impact of the study of these “workings of Nature” is leveraged dramatically by the extent to which the findings affect other disciplines and ventures. Specifically, the survey report and others go on to emphasize the importance of these investigations for understanding all solar system bodies, including our Earth, as well as astrophysical objects lying well beyond the reach of the Sun’s influence, where the same physics arises but is not directly observable, and the impact of such investigations on the study of the formation of solar systems and planetary systems, as well as the habitability of planetary systems.6,7 These reports point out that the fundamental physics of many important processes with wide application to laboratory and astrophysical plasma systems, for example, magnetic reconnection, are best addressed in the naturally occurring plasma environments available in the Sun-solar system domain.

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Review of Goals and Plans for NASA’s Space and Earth Sciences The Sun-Solar System Connection roadmap begins with a statement of its overriding objectives, which are specifically to (1) open the frontier to space weather prediction, (2) understand the nature of our home in space, and (3) safeguard our outward journey. The roadmap’s articulation of these objectives is based almost entirely on the applications of the science, even in justifying the investigation of the most fundamental processes. These largely utilitarian objectives flow down to research focus areas. Examples include “understand magnetic reconnection as revealed in solar flares, coronal mass ejections, and geospace storm” and “understand the causes and subsequent evolution of solar activity that affects Earth’s space climate and environment.”8 These focus areas have high intrinsic science merit. They are derivable from previous articulations of Sun-solar system goals before the advent of the exploration program.9,10 With the exception of some gaps, discussed below, the panel strongly endorses these focus areas. However, by justifying these objectives so strongly on the basis of their role in enabling the vision for space exploration and other utilitarian goals, the roadmap arrives at a science program that may not be robust to changes in the exploration vision and that in part releases NASA from its longstanding stewardship responsibilities of what the panel believes is a scientific endeavor that has high intrinsic merit irrespective of its important practical applications for achieving the exploration objectives. NASA has stewardship for this science program because progress in the Sun-solar system discipline relies overwhelmingly on space systems for obtaining measurements and because of NASA’s long-term investment in these areas. The panel strongly recommends that the connections of the Sun-solar system objectives and focus areas to the aspects of the Sun-solar system discipline with the highest scientific merit be articulated and maintained in any future promulgation of the Sun-solar system science and implementation program. This recommendation is not meant to replace the utilitarian flowdown; the “intrinsic scientific merit” flowdown is complementary. The panel also notes that the overwhelming reliance on a utilitarian flowdown can lead to gaps in the science program over which NASA has had, and should continue to have, stewardship. GAPS, CROSSCUTTING ISSUES, AND INFRASTRUCTURE The system science approach described above, whereby the sun-heliosphere-planetary atmospheres ensemble is studied as an integrated whole, requires simultaneous, coordinated measurements of many parameters at many places. The individual elements of the Sun-Solar System Connection roadmap tackle the fundamental physical processes, but the study of the integrated system can best be achieved if the individual assets operate together, as a system. The baseline roadmap plan spreads the elements out over time to such an extent that this necessary synergy risks being lost. The panel recommends that every effort be expended to better achieve the needed synergies between the different elements enabled by simultaneous observations from multiple locations and observing perspectives. In addition to trying to identify additional resources so that the more robust flight programs identified by the roadmap can be implemented, a stronger integration of non-NASA activities than that present in the roadmap should be pursued.11 Discussions of partnerships that NASA must have, or should develop, with the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the Department of Defense (DOD), and potentially with the Department of Energy (DOE) are not developed to the extent that they could be, given the scientific and programmatic potential.12 For example, the study of Earth’s ionosphere-thermosphere regions would be seriously deficient without the support of the NSF and DOD, and NOAA is the eventual intermediate customer, and eventual operator, of the space-weather predictive capabilities that are being developed as part of the Living with a Star program. The monitoring of the solar wind plasma and fields at the L1 position, between the Sun and Earth, is a good example of measurements that are essential for space weather operations and thus could be transitioned to NOAA. Partnerships with other countries, in particular with the European and Japanese Space Agencies, can help to increase the simultaneous coverage over more of the connected system.13 For example, the

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Review of Goals and Plans for NASA’s Space and Earth Sciences European Space Agency’s (ESA’s) Solar Orbiter mission could provide the simultaneous imaging of the solar source region for the solar wind plasma and energetic particles measured by NASA’s Inner Heliosphere Sentinels. ESA’s SWARM mission could provide limited ionosphere-thermosphere overlap with NASA’s Solar Dynamic Observatory. Partnerships with the other NASA discipline areas are also important and need to be explored further. There is a strong ongoing partnership with solar system exploration because the space environment is an integral part of planetary systems, with missions such as Voyager, Cassini, and the newly selected Juno carrying a complement of space physics instrumentation. The Sun-Earth system is the model for searches for Earth-like planets and habitable environments, and the Sun-solar system flagship mission, Stellar Imager, is devoted to resolving nearby stars, while the Interstellar Probe will provide in situ samples of the universe beyond the solar system. An L1 Earth-Sun joint mission with Earth sciences, with simultaneous solar and terrestrial observations, could be potentially rewarding but requires detailed study. The panel recommends that NASA proactively incorporate all of the partnership opportunities listed here in its planning activities to maximize the synergies in the measurement of different regions. The issue of the relative scarcity of missions in any one subdiscipline (solar, magnetospheric, and so on) also affects the infrastructure needed to sustain the science and technology necessary to achieve the roadmap objectives. Typically, Sun-solar system scientists develop most of their flight instrumentation, often in small university groups, and thus they are particularly vulnerable to a low mission flight rate and the diminishing suborbital program. Under the present program and the “realistic” Sun-solar system roadmap program, the survival of these groups would be jeopardized. The panel recommends that the issue of research group infrastructure be better incorporated into future promulgations of the Sun-solar system plans. The partnership opportunities discussed above can play a significant role here. The large-scale structure of the heliosphere and the interaction with the interstellar medium are not well addressed in the roadmap, and the Interstellar Probe flagship mission receives scant mention. In addition, the truly transformational, fundamental discovery science offered by the other flagship missions (Solar Probe, Stellar Imager), and by future Explorer missions developed as the requirements and opportunities arise, also appears as an orphan in the roadmap, achievable only by significant programmatic growth. Because of the importance that the panel places on the fundamental science in generating a science plan, while recognizing the importance of utilitarian objectives as well, the panel recommends that the need to address the science of these transformational missions, as well as fundamental physical processes of individual components of the system, be more prominently articulated in future promulgation of the Sun-solar system science objectives and implementation plan. REFERENCES 1. National Aeronautics and Space Administration (NASA), Advanced Planning and Integration Office. 2005. Sun-Solar System Connection. NASA, Washington, D.C. Available at <www.hq.nasa.gov/office/apio/pdf/sun/sun_roadmap.pdf>. 2. National Research Council (NRC). 2002. The Sun to the Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics. The National Academies Press, Washington, D.C. 3. NRC. 2002. The Sun to the Earth—and Beyond. 4. NRC. 2004. Solar and Space Physics and Its Role in Space Exploration. The National Academies Press, Washington, D.C. 5. NRC. 2002. The Sun to the Earth—and Beyond, p. 22. 6. NRC. 2002. The Sun to the Earth—and Beyond. 7. NRC. 2004. Plasma Physics of the Local Cosmos. The National Academies Press, Washington, D.C.

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Review of Goals and Plans for NASA’s Space and Earth Sciences 8. NASA, Advanced Planning and Integration Office. 2005. Sun-Solar System Connection, pp. 11-14. 9. NRC. 2002. The Sun to the Earth—and Beyond. 10. NRC. 2004. Solar and Space Physics and Its Role in Space Exploration. 11. NRC. 2002. The Sun to the Earth—and Beyond. 12. NRC. 2002. The Sun to the Earth—and Beyond. 13. NRC. 2002. The Sun to the Earth—and Beyond.