and Germany’s AsteroidFinder are interesting and capable small-scale missions that will detect a small percentage of specific types of NEOs, those primarily inside Earth’s orbit. These spacecraft will not accomplish the goals of the George E. Brown, Jr. Near-Earth Object Survey Act of 2005. However, they highlight the fact that other countries are beginning to consider the NEO issue seriously. Such efforts also represent an opportunity for future international cooperation and coordination in the search for potentially hazardous NEOs. In addition, the committee was impressed with the European Space Agency’s early development of the Don Quijote spacecraft mission, which would consist of an observing spacecraft and a kinetic impactor. This mission, though not funded, would have value for testing a mitigation technique and could still be an opportunity for international cooperation in this area.

Finally, the committee points out a current estimate of the long-term average annual human fatality rate from impactors: slightly under 100 (Harris, 2009). At first blush, one is inclined to dismiss this rate as trivial in the general scheme of things. However, one must also consider the extreme damage that could be inflicted by a single impact; this presents the classic problem of the conflict between “extremely important” and “extremely rare.” The committee considers work on this problem as insurance, with the premiums devoted wholly toward preventing the tragedy. The question then is: What is a reasonable expenditure on annual premiums? The committee offers a few possibilities for what could perhaps be accomplished at three different levels of funding (see Chapter 8); it is, however, the political leadership of the country that determines the amount to be spent on scanning the skies for potential hazards and preparing our defenses.

REFERENCES

Boslough, M., and D. Crawford. 2008. Low-altitude airbursts and the impact threat. International Journal of Impact Engineering 35:1441–1448.

Boslough, M.B.E., and D.A. Crawford. 1997. Shoemaker-Levy 9 and plume-forming collisions on Earth. Near-Earth Objects, the United Nations International Conference: Proceedings of the International Conference held April 24-26, 1995, in New York, N.Y. (J.L. Remo, ed.). Annals of the New York Academy of Sciences 822:236–282.

Chyba, C.F., P.J. Thomas, and K.J. Zahnle. 1993. The 1908 Tunguska explosion—Atmospheric disruption of a stony asteroid. Nature 361:40–44.

Harris, A.W., Space Science Institute. 2009. The NEO population, impact risk, progress of current surveys, and prospects for future surveys, presentation to the Survey/Detection Panel of the NRC Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies, January 28–30, 2009.

NRC (National Research Council). 2009. Near-Earth Object Surveys and Hazard Mitigation Strategies: Interim Report, The National Academies Press, Washington, D.C., available at http://www.nap.edu/catalog.php?record_id=12738, pp. 1-2.



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