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The surface textures of polyimide (PI) films exposed to a low Earth orbit environment in the “SM and JEM/MPAC&SEED experiments” and PI films irradiated by atomic oxygen (AO) using a ground facility were quantitatively evaluated. Additionally, the degradation in tensile strength of these PI films was assessed in terms of the surface texture changes. The exposed surfaces of the flight PI films were contaminated by silicon oxide layers and included some local valleys, or extremely deep depressions compared with the surrounding areas. The depth of the deepest local valleys on the exposed surfaces (a 0max ), which were predicted by extreme statistics, exceeded those of the local valleys of the AO-irradiated PI films. When the tensile strength of these PI films was plotted against AO fluence, the tensile strength reduction trends clearly differed for each PI film. However, the reduction trends were shown to closely correlate when the tensile strengths were plotted against a 0max . These results mean that the tensile strength of the PI films attacked by AO can be evaluated based on the depth of surface cracks and that fracture mechanics is considered an effective tool to predict tensile strength reduction.

A space materials exposure experiment was conducted on the exterior of the International Space Station (ISS) using the Micro-Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). The MPAC&SEED experiments were aboard both the Russian Service Module (SM/MPAC&SEED) and the exposed Facility of the Japanese Experiment Module, KIBO Exposed Facility (JEM/MPAC&SEED). The JEM/MPAC&SEED was attached to the Space Environment Data Acquisition Equipment-Attached Payload (SEDA-AP).

Extreme ultraviolet (EUV) spectrum emitted from laser-sustained oxygen plasma in a laser detonation atomic oxygen beam source was investigated. In order to measure EUV spectra, specially designed flat-field grazing-incidence EUV spectrometer was designed. The EUV spectra were recorded on an imaging plate which provides quantitative analysis capability. It was confirmed that EUV emission in the range of 20 –50 nm was included in the emission from laser-sustained oxygen plasma in a laser detonation source. The experimental results clearly indicated that the EUV intensity depends strongly on the translational energy of atomic oxygen. Even though the effect of EUV on the material erosion has not been confirmed, presence of high-energy photon need to be considered for better understanding of the reaction of hyperthermal atomic oxygen in the ground-based facility.