high-energy protons for a number of biological end points and the efficacy of different types and thicknesses of shielding in reducing these risks. These recommendations are described in more detail in Appendix A.

NASA’s Strategic Program Plan for Space Radiation Health Research (NASA, 1998) was approved in October 1998 by the associate administrator for the Office of Life and Microgravity Sciences and Applications. The budget breakdown for FY 1999 is given in Table 8.1. The program follows closely the principal recommendations of the Strategy report, which were given as experimental procedures designed to answer higher- and lower-priority research questions. The higher-priority recommendations were aimed at determining the carcinogenic risk and effects on the CNS of exposure to energetic protons and HZE particles; how the composition of the shielding would quantitatively ameliorate the biological effect of HZE particles; and whether there are studies on radiation-induced genetic changes that could increase confidence in extrapolating from rodents to humans and might enhance a similar extrapolation for cancer. Other high-priority recommendations were to determine if there were better analyses that could decrease the present uncertainties in the risks of HZE effects, to determine how the design of the space vehicle could affect the internal radiation levels, and to determine whether SPEs could be predicted with sufficient advance warning for astronauts to return to a shielded shelter. Low-priority recommendations were to estimate the effects of long-duration flight on fertility and on cataract formation, to