I. Introduction
Many highly disordered insulating materials used in spacecraft construction can exhibit electron-induced glow or cathodoluminescence when exposed to the space plasma environment [1]–[3]. Determinations of the absolute and relative cathodoluminescent intensity of spacecraft materials per incident electron flux are essential to predict and mitigate consequences for stray light contamination in space-based observatories [1]–[4] and optical detection [5]. They also provide important information about the defect structure and electron transport properties of these materials [6]–[10].