found a need for the development and launch of constellations of spacecraft, which are necessary to provide simultaneous measurements from broad regions of space and thereby separate spatial from temporal effects to reveal the true couplings between adjacent regions of space. By necessity, constellation missions require large investments, and their design, assembly, and execution are challenging. The expected budget profile for NASA’s Heliophysics program is such that launch of the next major mission in heliophysics cannot be reasonably expected before 2024, or 6 years after SPP. This constraint—and not the absence of proposals to undertake compelling science investigations—defines a cadence for major missions.

In contrast to the STP program, which the survey committee recommends be community-based like the Explorers, major missions are appropriately undertaken by NASA centers. NASA’s LWS program is the proper vehicle for large-class, center-led, major missions. In Chapter 4 the survey committee describes the next science target best addressed by the LWS program when the budget of the Heliophysics Division allows: a mission to understand how Earth’s atmosphere absorbs solar wind energy, illustrated by the Geospace Dynamics Constellation (GDC).


The foundational assets described above form the cornerstones of the solar and space physics research program for the coming decade. Each is of exceptional importance; however, maximizing science return while operating in a highly constrained fiscal environment requires that they be prioritized and then implemented at an appropriate cadence. Further, a strategy is needed to address unforeseen technical or budgetary problems, such as budget problems attributable to the cost growth of individual program elements or unexpected changes in the overall (top-line) budget. Described below is the survey committee’s approach to prioritizing program elements and formulating decision rules to address budget shortfalls.

Funding Priorities for NASA’s Heliophysics Program

By employing the assets described above at an appropriate cadence, and using the decision rules described below, a viable program can be crafted that should allow solar and space physics to preserve the strategic goal of balanced progress even under less favorable budgetary circumstances. The DRIVE initiative has the fastest cadence (new competitions annually for many of its components), followed by a 2- to 3-year cadence for the Explorer program, a 4-year cadence for the moderate-scale mission STP program, and a 6-year cadence for the LWS major mission program. It follows that the first new NASA implementation priority is the augmentation required by the DRIVE initiative, followed by the augmentation for the Explorer program, the initiation of the STP moderate-scale mission program, and finally the continuation of the LWS major mission program. Chapter 6 provides a detailed discussion of the survey committee’s proposed implementation of these program elements within the budget projected by NASA over the next 5 years and extrapolated by the committee for an additional 5 years.

Decision Rules

Decision rules are strategies to preserve an orderly and effective program for solar and space physics in the event that less funding than anticipated is available, or some other disruptive event occurs. As described in more detail in Chapter 6, the rules, with one exception, affect the year that mission and foundational activities commence and the cadence at which they repeat in the coming decade. The survey committee also provides decision rules to aid in implementing a program under a more favorable budget. In particular,

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