•   Planning for future exploration of Titan and Enceladus. Interest in a follow-on mission to Cassini-Huygens has focused on the development of the NASA-ESA Titan Saturn System Mission. This concept envisages the deployment of two ESA-supplied in situ elements—a lake lander and a hot-air balloon—delivered by a large and complex NASA-supplied orbiter. Studies of Enceladus could occur before or after orbiting Titan. An alternative mission plan describes a stand-alone Enceladus orbiter. See Appendix B.

•   The initiation of the New Frontiers mission line. The initiation of the New Frontiers line of principal investigator-led, medium-cost missions represents an important legacy of the first planetary science decadal survey. New Frontiers missions selected by NASA that will target the outer solar system include the New Horizons mission to Pluto-Charon and the Juno mission to Jupiter. The latter will invoke a planetary protection plan that relies on the findings and recommendations of the NRC’s 2000 Europa report. The most recent planetary decadal survey identified several additional New Frontiers candidates relevant to the subject matter of this report.

•   Possibility of Discovery-class missions to outer solar system bodies. With the exception of New Horizons and Juno, all expeditions to the outer solar system launched to date correspond to flagship-class missions. The complex power and communications systems required for spacecraft that venture beyond the asteroid belt generally exceed the cost caps of principal investigator-led Discovery missions. The need to flight-test the newly developed Advanced Stirling Radioisotope Generator (ASRG) has opened the outer solar system to smaller missions. The most recent competition for Discovery missions allowed for the potential use of two ASRGs at no expense to the principal investigator. One of the three proposals selected for additional study was the Titan Mare Explorer (TIME), a lake lander. The potential selection of TIME and the possibility of future ASRG-powered Discovery missions to destinations in the outer solar system raise important questions. The one most relevant to this study concerns the compatibility between the financial and temporal constraints placed on the development and launch schedule of Discovery missions and the constraints placed by the potential implementation of complex planetary protection measures. See Appendix B.

REFERENCES

1. National Research Council, Vision and Voyages for Planetary Science in the Decade 2013-2022, The National Academies Press, Washington, D.C., 2011, pp. 11 and 75-78.

2. United Nations, Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies, U.N. Document No. 6347, Article IX, January 1967.

3. COSPAR, “COSPAR Planetary Protection Policy (20 October 2002; As Amended to 24 March 2011),” COSPAR, Paris, p. 1, available at http://cosparhq.cnes.fr/Scistr/PPPolicy%20(24Mar2011).pdf.

4. National Research Council, Preventing the Forward Contamination of Europa, National Academy Press, Washington, D.C., 2000.

5. National Research Council, A Review of Space Research, National Academy of Sciences, Washington, D.C., 1961, p. 10.9.

6. National Research Council, Preventing the Forward Contamination of Europa, National Academy Press, Washington, D.C., 2000, p. 23.

7. COSPAR, “COSPAR Planetary Protection Policy (20 October 2002; As Amended to 24 March 2011),” COSPAR, Paris, p. A1, available at http://cosparhq.cnes.fr/Scistr/PPPolicy%20(24Mar2011).pdf.

8. National Research Council, A Science Strategy for the Exploration of Europa, National Academy Press, Washington, D.C., 1999, p. 64.

9. National Research Council, New Frontiers in the Solar System: An Integrated Exploration Strategy, The National Academies Press, Washington, D.C., 2003, pp. 5 and 196-199.

10. National Research Council, Vision and Voyages for Planetary Science in the Decade 2013-2022, The National Academies Press, Washington, D.C., 2011, pp. 269-271.

11. Personal communication to the committee, Christopher Chyba, October 2011.

12. COSPAR Panel on Planetary Protection, COSPAR Workshop on Planetary Protection for Outer Planet Satellites and Small Solar System Bodies, European Space Policy Institute, Vienna, Austria, 2009.

13. COSPAR Panel on Planetary Protection, COSPAR Workshop on Planetary Protection for Titan and Ganymede, COSPAR, Paris, France, 2010.



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