Satellite Anomalies from Galactic Cosmic Rays

Abstract

Anomalies in communication satellite operation have been caused by the unexpected triggering of digital circuits. Interactions with galactic cosmic rays were investigated as a mechanism for a number of these events. The mechanism assumed was the charging of the base-emitter capacitance of sensitive transistors to the turn-on voltage. The calculation of the cosmic ray event rate required the determination of transistor parameters, charge collection efficiencies, and the number of sensitive transistors. The sensitive transistors were determined by analyzing the results of a scanning electron microscope experiment. Calculations with iron cosmic rays resulted in an event rate of 3.1 × 10-3 per transistor per year, in reasonable agreement with the observed rate of 1.5 × 10-3.