METHOD FOR ESTIMATING SPONTANEOUS PULSE-RATE FOR INSULATORS INSIDE SPACECRAFT

High energy electrons that penetrate the thin surface materials on spa cecraft can be stopped in insulated materials inside spacecraft and th ereby generate spacecharge-caused electric fields and high voltages in side the spacecraft. The fields are large enough to induce spontaneous pulsing by insulating materials. Realistic estimates of pulse rates a re currently lacking. The frequency of electrostatic discharge pulsing can be estimated by extrapolating the pulse rate measured for insulat ors on the CRRES spacecraft. The extrapolation is based upon CRRES dat a which show that: 1) The pulse rate scales with high energy electron flux, and with the area and type of insulator. 2) Samples must be soak ed in vacuum for at least six months before being tested so that the r esults are not biased by species such as water and free radicals that eventually outgas. 3) Insulators containing many large imperfections s uch as the glass fibers in epoxy fiberglass circuit boards produce the most frequent pulsing. 4) Some insulators pulse only rarely. 5) We ha ve not yet determined a high energy electron flux below which no pulsi ng occurs.