IV-10 The fourth and fifth items in table 1 provide detailed information on spectral energy composition for aluminum shield thicknesses of 0, 50, 500, 1000, 2000, 4000, and 7000 mils. The inclusion of predictions for very thick shielding is appropriate for the manned bays in ISSA, but is atypical for unmanned vehicles. Items six and seven in table 1 address the peak proton flux expected from trapped protons during passages through the South Atlantic Anomaly. Note that the peak flux occurring due to trapped protons is almost always lower than the peak flux due to solar particle events, with the exception being low inclination LEO orbits. However the SAA is encountered on about 50% of ISSA orbits (several times a day) as opposed to the relatively rare solar events. In this case, the peak from SAA trapped protons, integrated over energies > 10 MeV, is 2.04 X 103 p/cm2/s, which is 54 times the orbit- averaged rate. Table 1, items nine and ten describe the modeled peak rates corresponding to solar particle events, including effects of the Earth's geomagnetic shielding. Data listed in these tables indicate an expected peak (for design purposes) of 3.36 X 10 p/cm2/s. This is 165 times the peak rate during SAA passages. This event would be expected, as described in [SSP-30512], once per 11 year solar cycle, or approximately once per mission for ISSA. Peak proton arrival rates for a given mission cannot be predicted in a deterministic manner. The use of the October 1989 flare as a design environment, shown in figure 4, for ISSA is a somewhat arbitrary choice. Other options exist, including other peak solar particle models incorporated in CREME-96 [Tylk-96, Tylk-96a]. More recently, a probabilistic model for predicting peak flux based on solar cycles 20, 21, and 22 has been proposed [Xaps- 98], and this allows a more quantitative approach to assessing the risk of exceeding a given proton flux. Please see the discussion of peak SPE proton rates in the 1997 Short Course notes [Bart-97] for more information and discussion on 