Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
ENABLING DISCOVERY IN SOLAR AND SPACE PHYSICS
33
energy and plasma at the foundation of the Sun’s atmosphere. In summary, Explorers are among the most
competitive solicitations in NASA science, and they offer relatively frequent opportunities for all researchers
to propose new and exciting ideas that are selected on the basis of science content, relationship to overall
NASA strategic goals, and feasibility of execution.
The survey committee believes that an adequate cadence for Heliospheric Explorers is one mission
every 2 to 3 years, a rate that was possible before the major reduction in 2005 in the Explorer program.
The survey committee also notes that competition for the MIDEX class of Explorers, which historically
has offered an opportunity to resolve the highest-level science questions, has not been possible under the
current Explorer budget. Finally, the survey committee notes that the Explorer program is the home for
Missions of Opportunity, which make it possible to achieve fundamental science at a fraction of the cost of
stand-alone missions by hosting payloads through partnering with other agencies, nations, or commercial
spaceflight providers. For example, the Solar-C mission now confirmed by Japan presents a future opportunity for the United States to provide instrumentation to a major foreign mission and in so doing to obtain
a high science return for relatively low cost. Thus, an augmentation to the Explorer program and restoration of the MIDEX component of Explorers, described in detail in Chapter 4, are required to achieve the
optimal cadance and to leverage resources with commercial, interagency, and international opportunities.
Moderate-Scale Space Missions
Many of the most important solar and space physics science questions cannot be addressed by
Explorer-class missions. The survey committee has considered the most critical topics that can be realistically addressed by moderate-scale NASA missions and lists the community’s top three priorities below
(see Chapter 4 for details). To achieve an acceptable flight rate, the survey committee recommends that
the Heliophysics Division’s Solar-Terrestrial Probes (STP) program be reconfigured as a moderate-mission
program modeled after the successful Discovery and New Frontiers programs of NASA’s Planetary Science Division. Like these planetary missions, the new Solar-Terrestrial Probes should be led by a principal
investigator, selected competitively, cost-capped, and managed in a manner similar to Explorers. Such
programs exhibit superior cost-performance history compared with the more traditional mode for major
missions (see Appendix E).
The survey committee believes that an adequate cadence for moderate-scale space missions is one
every 4 years. In view of the expected budget constraints discussed below, it is evident that it will not
be possible to achieve this cadence until the end of the decade. Although moderate missions are to be
selected competitively, each moderate mission’s science goal has to be defined in advance to achieve the
strategic objective of balanced progress.
In Chapter 4, the survey committee presents the rationale for and priority order of science investigations
that best achieve these objectives. In descending order for implementation they are as follows:
1. A mission to understand the interaction of the outer heliosphere with the interstellar medium—one
that will be coordinated with NASA’s Voyager mission and will also provide critical data on solar wind
inputs to the terrestrial system. An illustrative example is the Interstellar Mapping and Acceleration Probe
(IMAP).
2. A mission designed to substantially advance understanding of the variability in space weather driven
by lower-atmosphere weather on Earth, illustrated by the Dynamical Neutral Atmosphere-Ionosphere Coupling (DYNAMIC) mission.
3. A mission that probes how the magnetosphere-ionosphere-thermosphere system is coupled and how
it responds to solar and magnetospheric forcing, illustrated by the Magnetosphere Energetics, Dynamics,
Solar and Space Physics: A Science for a Technological Society
ENABLING DISCOVERY IN SOLAR AND SPACE PHYSICS
33
energy and plasma at the foundation of the Sun’s atmosphere. In summary, Explorers are among the most
competitive solicitations in NASA science, and they offer relatively frequent opportunities for all researchers
to propose new and exciting ideas that are selected on the basis of science content, relationship to overall
NASA strategic goals, and feasibility of execution.
The survey committee believes that an adequate cadence for Heliospheric Explorers is one mission
every 2 to 3 years, a rate that was possible before the major reduction in 2005 in the Explorer program.
The survey committee also notes that competition for the MIDEX class of Explorers, which historically
has offered an opportunity to resolve the highest-level science questions, has not been possible under the
current Explorer budget. Finally, the survey committee notes that the Explorer program is the home for
Missions of Opportunity, which make it possible to achieve fundamental science at a fraction of the cost of
stand-alone missions by hosting payloads through partnering with other agencies, nations, or commercial
spaceflight providers. For example, the Solar-C mission now confirmed by Japan presents a future opportunity for the United States to provide instrumentation to a major foreign mission and in so doing to obtain
a high science return for relatively low cost. Thus, an augmentation to the Explorer program and restoration of the MIDEX component of Explorers, described in detail in Chapter 4, are required to achieve the
optimal cadance and to leverage resources with commercial, interagency, and international opportunities.
Moderate-Scale Space Missions
Many of the most important solar and space physics science questions cannot be addressed by
Explorer-class missions. The survey committee has considered the most critical topics that can be realistically addressed by moderate-scale NASA missions and lists the community’s top three priorities below
(see Chapter 4 for details). To achieve an acceptable flight rate, the survey committee recommends that
the Heliophysics Division’s Solar-Terrestrial Probes (STP) program be reconfigured as a moderate-mission
program modeled after the successful Discovery and New Frontiers programs of NASA’s Planetary Science Division. Like these planetary missions, the new Solar-Terrestrial Probes should be led by a principal
investigator, selected competitively, cost-capped, and managed in a manner similar to Explorers. Such
programs exhibit superior cost-performance history compared with the more traditional mode for major
missions (see Appendix E).
The survey committee believes that an adequate cadence for moderate-scale space missions is one
every 4 years. In view of the expected budget constraints discussed below, it is evident that it will not
be possible to achieve this cadence until the end of the decade. Although moderate missions are to be
selected competitively, each moderate mission’s science goal has to be defined in advance to achieve the
strategic objective of balanced progress.
In Chapter 4, the survey committee presents the rationale for and priority order of science investigations
that best achieve these objectives. In descending order for implementation they are as follows:
1. A mission to understand the interaction of the outer heliosphere with the interstellar medium—one
that will be coordinated with NASA’s Voyager mission and will also provide critical data on solar wind
inputs to the terrestrial system. An illustrative example is the Interstellar Mapping and Acceleration Probe
(IMAP).
2. A mission designed to substantially advance understanding of the variability in space weather driven
by lower-atmosphere weather on Earth, illustrated by the Dynamical Neutral Atmosphere-Ionosphere Coupling (DYNAMIC) mission.
3. A mission that probes how the magnetosphere-ionosphere-thermosphere system is coupled and how
it responds to solar and magnetospheric forcing, illustrated by the Magnetosphere Energetics, Dynamics,