ttle benefit. Figure 6-4 indicates the attenuation provided by various levels of shielding for the trapped proton spectrum present in the CRRES orbit. Figure 6-5 indicates the attenuation provided by various levels of shielding for the trapped proton spectrum present in a 1400 km, 50° inclined orbit. Attenuation of the integral spectrum at 10 MeV indicates that a shielding increase from 200 mils to 400 mils reduces the flux by 32% for the CRRES orbit, and 16% for the 1400 kilometer orbit. Shielding increase from 200 mils to 800 mils reduces the flux by 63% for the CRRES orbit, and 34% for the 1400 km orbit. COSMIC RAY INTEGRAL SPECTRA Z = 1 92 Al Shielding 100 mils 200 mils 500 mils 1000 mils 2000 mils 3500 mils 5000 mils LET (MeV/g/cm²) Figure 6-3. Galactic Cosmic Ray Heavy Ion Integral Flux Spectra [Petersen97] 1.00E+03 9.00E+02 8.00E+02 200 mils 7.00E+02 400 mils 6.00E+02 800 mils 5.00E+02 4.00E+02 3.00E+02 2.00E+02 1.00E+02 0.00E+00 Energy [MeV] Figure 6-4. CRRES Orbit Trapped Proton Integral Spectrum 2.50E+03 2.00E+03 200 mils 1.50E+03 400mils 800 mils 1.00E+03 5.00E+02 0.00E+00 Energy [MeV] Figure 6-5. 1400 km Orbit Trapped Proton Integral Spectrum Analysis of shielding conditions within the spacecraft must be performed to establish the distribution of solid angle percentage as a function of shielding thickness. Previous analyses of this type have shown typical shielding thickness of 250 mils on satellites, instead of the typical 100 mil value which is often specified. Spacecraft in development now and next generation systems are making use of thinner, stronger, and lightweight materials; analysis of the shielding conditions specific to the spacecraft under development must be performed. Some limited attenuation of proton single event upset rate is achievable by management of component location and the use of additional shielding; estimates range from 15% to 50% reduction in trapped proton induced SEU rate. No appreciable benefit is realized from consideration of such provision for galactic cosmic ray heavy