Low-Energy Electron Exposure of Space Materials

A laboratory test, which exposed a variety of spacecraft thermal control and optical materials to low-energy (500 eV) electron radiation, was performed to investigate the response of these materials to electrons with energies below 1 keV. The potential importance of these low-energy electrons is exemplified by the fact that current environment models indicate as much as 30-40% of the geosynchronous electron environment is composed of electrons with kinetic energy of less than 1 keV. There exist recently published geosynchronous-Earth-orbit flight data for electron energies down to approximately 40 eV, which now allows for enhancement of the limited and outdated, but still commonly used, space environment model AE8. Some limitations of prevailing particulate radiation transport codes also exist, as many are often unable to make reliable predictions for particle energies below 1 keV. The presented test data demonstrate that measurable changes result in several space materials from exposure to high fluences of 500 eV electrons The material changes are compared with prior tests results and shown to be a significant fraction of changes induced by orbital and multi-energy-electron exposures.