Damage Effects Of Space Dust And Atomic Oxygen Environment On Conductive Second Surface Mirror

Polyimide film is an important type of thermal control coatings used in spacecraft. In this paper, two kinds of modified Polyimide films, conductive polyimide aluminum-coating second surface mirror (ITO/Kapton/Al) and conductive atomic oxygen resistance polyimide aluminum-coating second surface mirror (ITO/SiOx/Kapton/Al) were experienced atomic oxygen exposure and space dust impact experiment to test their space stability. Before and after the as-desired experiments, changes in optical and electrical properties were studied by analysis the mass loss, surface morphology, diffuse reflectance and electrical conductivity. And then the damage mechanism was well explored.It is showed that the mass loss of Kapton films in the atomic oxygen exposure experiment is mostly proportional to the atomic oxygen erosion effects, which is in well accordance with the mass loss equation obtained by many researchers. After atomic oxygen exposure, the optical properties of the films have an apparent decrease. The high the atomic oxygen dose, the low the diffuse reflectance. Meanwhile, the decrease in the diffuse reflectance spectra shifted from UV region to infrared region, which also indicating that the optical properties of the conductive thin film has a serious degradation. After atomic oxygen erosion, the electrical resistivity of the Man-made folding polyimide film has drop about 2 orders magnitude, exhibiting more serious degradation in electrical performance compare to the normal conductive second surface mirror.After space dust impact test, from the SEM imagines we can see that the smooth flat surface of the ITO/Kapton/Al changed to a rugged topography state, which is called "sand erosion" phenomenon. The space dust induced damage conditions of the films varied with the impact angles, When the incident angle is 90°to the film, the morphology of the damage area of the ITO/Kapton/Al is roughly circular-like, while the 45°impact angle lead to mostly scratch surface damage. In addition, the 45°impact angle also induced compression deformation. After dust impact test, the diffuse reflectance of the films exhibited a slightly decrease, mainly in the visible and ultraviolet regions.