Effects of Ultraviolet Irradiation and Atomic Oxygen Erosion on Total Electron Emission Yield of Polyimide

Polymers used on low earth orbit (LEO) spacecraft surface suffer from an ultraviolet (UV) irradiation and orbital atomic oxygen (AO) erosion. These degradations may change the total electron emission yield (TEEY) of the materials and ultimately result in unexpected surface charging. In this paper, we chose polyimide (PI) film, a thermal control material, and carried out two types of ground-based degradation. The degradation methods were UV irradiation with five different equivalent solar hours, and AO erosion with two fluences equivalent to 0.5 and 1 year LEO flight time, respectively. Using an Auger microscope-based TEEY measurement system with a scanning measuring method, the TEEY of virgin and degraded PI films were tested and analyzed comparatively. The X-ray photoelectron spectrum, field-emission scanning electron microscope, and computational simulations were also used for element bonds analysis, roughness imaging, and electron depth calculation to discover the mechanisms of the degradation and their effects on the TEEY of the material.