ze, suggesting that SEU sensitivity will be kept above the alpha-particle limit by manufacturers [207]. II-64 tolerant systems are routinely used in aircraft mechanical systems and seem a natural choice for preventing neutron-induced SEU in avionics [322]. SOI is a possible solution to the terrestrial SEU problem, although as noted previously SOI is not automatically upset immune. Manufacturers have demonstrated the ability to produce ultra large-scale SOI DRAMs [323], microprocessors [324], and SRAMs [325], although others remain skeptical of the advantages of SOI [326]. In any event, the fact that commercial manufacturers will be studying SEU should prove beneficial to the radiation effects community inasmuch as it brings new resources to bear on the problem. II-65 SUMMARY AND CONCLUSIONS In this short course segment we began with a review of the radiation environment encountered by space telecommunications systems. In general, the environment consists of trapped and transient protons, heavy ions, and electrons. Because electrons are rarely important for SEE, they were not treated in this segment. Protons are trapped by the Earth's magnetic field in two belts around the planet, an inner belt and an outer belt. Trapped heavy ions also exist but are not in general energetic enough to cause SEE in shielded systems. The South Atlantic Anomaly is a localized region of intense proton flux at low altitudes (<3000 km) and is an important SEE threat for systems operating in low Earth orbits. Transient particles (protons and heavy ions) ejected by solar events are also important contributors to SEE. Solar events follow a several-year cyclical variation but can occur at any time and produce large particle fluences. The galactic cosmic ray background is inversely proportional to the solar cycle and produces high- energy heavily-ionizing particles. Secondary neutrons and protons are produced by the interaction of galactic cosmic rays with the atmosphere and are important for terrestrial and high-altitude Non-destructive SEE