can be adjudicated. Ancillary developments in areas such as communications and spacecraft subsystems will be needed to allow full use of these technologies.

Although the solar and space physics community has made use of RPS in the past and will certainly utilize emerging RPS technologies, nuclear-electric propulsion enables a much different and larger class of missions. An appropriate strategy is to pursue nuclear propulsion technologies as long as they do not interfere with the current diversity of solar and space physics missions. Such diversity gives scientific breadth and depth to these pursuits and is essential for the long-term health and vitality of solar and space physics as a discipline.

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2. Assembly of Mathematical and Physical Sciences, National Research Council, Astronomy and Astrophysics for the 1980’s, National Academy Press, Washington, D.C., 1982.

3. National Research Council, Space Science in the Twenty-First Century: Imperatives for the Decades 1995 to 2015—Solar and Space Physics, National Academy Press, Washington, D.C., 1988, pp. 41–43.

4. National Research Council, A Science Strategy for Space Physics, National Academy Press, Washington, D.C., 1995, pp. 3, 37, 66, and 74.

5. National Research Council, The Sun to the Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics, The National Academies Press, Washington, D.C., 2003.

6. Interstellar Probe Science and Technology Definition Team, NASA, Interstellar Probe: Exploring the Interstellar Medium and the Boundaries of the Heliosphere, Jet Propulsion Laboratory, Pasadena, Calif., 1999, available only online at <http://interstellar.jpl.nasa.gov/> last accessed February 2, 2006.

7. National Research Council, The Sun to the Earth—and Beyond: Panel Reports, The National Academies Press, Washington, D.C., 2003, pp. 36–38.

8. National Research Council, The Sun to the Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics, The National Academies Press, Washington, D.C., 2003, p. 78.

9. N.J. Shaviv, “The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth,” New Astronomy 8: 39–77, 2003.

10. G.M. Raisaisbeck, F. Yiou, M. Fruneau, J.M. Loiseaux, M. Lieuvin, J.C. Ravel, and C. Lorius, “Cosmogenic ¹⁰Be concentrations in Antarctic ice during the past 30,000 years,” Nature 292: 825–826, 1981.

11. J. Beer, U. Siegenthaler, and A. Blinov, “Temporal ¹⁰Be Variations in Ice; Information on Solar Activity and Geomagnetic Field Intensity,” pp. 297–313 in Secular Solar and Geomagnetic Variations in the Last 10,000 Years, F.R. Stephenson and A.W. Wolfendale, eds., Kluwer Academic Publishers, Dordrecht, the Netherlands, 1988.

12. National Research Council, The Astrophysical Context of Life, The National Academies Press, Washington, D.C., 2005, pp. 20–21.

13. S.A. Gavit, “Interstellar Probe Mission Architecture and Technology Report,” Internal document JPL-D-18410, Jet Propulsion Laboratory, Pasadena, Calif., 1999.

14. National Research Council, The Sun to the Earth—and Beyond: Panel Reports, The National Academies Press, Washington, D.C., 2003, p. 38.

15. Congressional Budget Office, A Budgetary Analysis of NASA’s New Vision for Space Exploration, Congress of the United States, Washington, D.C., 2004, p. 22.

16. For more details about Solar Probe see, for example <sec.gsfc.nasa.gov/solarprobe/solarprobe.htm>.

17. For more details on Solar Probe see, for example, Applied Physics Laboratory and Jet Propulsion Laboratory, Solar Probe: An Engineering Study, NASA-Goddard Spaceflight Center, Greenbelt, Md., 2002. Available at <http://solarprobe.gsfc.nasa.gov/solarprobe_apl_study.pdf> last accessed February 2, 2006.

18. See, for example, J.X. Luu and D.C. Jewitt, “Kuiper Belt Objects: Relics from the Accretion Disk of the Sun,” Annual Reviews of Astronomy and Astrophysics 40: 63–101, 2002.

19. See, for example, E.W. Hones, Jr., “On the Use of Positrons as Tracers to Study the Motions of Electrons Trapped in the Earth’s Magnetosphere,” Journal of Geophysical Research 69: 182–185, 1964.