Single event upsets of spacecraft microelectronics exposed to solar cosmic rays.

The technique for evaluating the SEU rate induced by solar particle incidence on spacecraft microelectronics is described, including the contributions from the primary (heavy ion-induced) and secondary proton-induced) SEU mechanisms. The technique is based on original computational models for solar particle energy spectra and for SEU occurrence in electronics. The technique was used to analyze the data of the TDRS-1 Fairchild 93L422 IC exposed to protons and ions during the solar cosmic ray event of September-October 1989. The analysis included the distribution of the microcircuit shielding. A strong dependence of solar proton-to-ion ratio on the shielding thickness was indicated by the calculations.