Changes of the Electrical and Optical Character of Polyimide Films (and the Chemistry that Drives Them) Due to Exposure to High Energy GEO-like Electrons

1. ABSTRACT As a result of the interaction between the spacecraft and its operational environment, the constituent materials begin to change. These changes are determined by a combination of energy deposition, the resulting chemical reactions, and contamination. These changes negatively impact the ability of spacecraft operators to predict the behavior of a spacecraft as it ages. For example, in the case of electrical conduction in polyimide, there is a three orders of magnitude decrease in the resistivity after only eight months of simulated GEO electron exposure. This will affect the results of models designed to predict the spacecraft electric potential a spacecraft will adopt and could lead operators to fly a spacecraft in unsafe conditions. Optical changes in the material also dramatically impact the ability of ground based optical observations to identify and track both known and unknown spacecraft.