The Hinode (Solar-B) Solar Optical Telescope (SOT) is sensitive to molecular contaminant deposition resulting from its organic materials outgassing on orbit. It was launched by M-V rocket on 22 September 2006 UT. The SOT telemetry data showed that temperature of the Heat Dump Mirror (HDM) rose rapidly during first two months, and that the SOT throughput at shorter wavelength decreased linearly over one year. These are attributed to the facts that molecular contamination deposition degrades a solar absorptance of the HDM, the reflectance of the Primary Mirror and the Secondary Mirror, and the transmittance of the Collimating Lens. The numerical analyses of molecular contamination deposition were conducted in order to identify a major contaminant source and contaminated optics. We found that a major contaminant source was silicone sealant DC6-1104 which was used in the Collimating Lens Unit.
JAXA is developing a contamination analysis tool "J-SPICE" (Japanese Spacecraft Induced Contamination analysis software). Generally speaking, contamination analysis tools predict based on various input data and mathematical models of contaminant behavior, which means prediction accuracy depends on the validity of mathematical models as well as of input data. We investigated the validity of a diffuse reflection model applied in J-SPICE by comparing the reflection flux of contaminant molecules measured by the ground experiment and the analytical result of the J-SPICE. The result showed that the diffuse reflection model of J-SPICE reasonably explains molecule distribution reflected by a flat surface.
Japan Aerospace Exploration Agency (JAXA) deployed three identical Micro-Particles Capturer (MPAC) units on the exterior of the Russian Service Module (SM) on the International Space Station (ISS). MPAC is a passive experiment designed to evaluate micrometeoroids and space debris environment on ISS orbit. Silica aerogels were mounted on MPAC units to capture those particles. However, it was found that the surface of silica aerogel had been altered by space environment during the experiment. Therefore, we evaluated the effects of atomic oxygen and ultraviolet rays on silica aerogel. The experimental results suggested that AO caused small cracks on silica aerogel surface, however, surface morphological feature observed in silica aerogel on SM/MPAC could not be reproduced by AO or UV-exposures. Contribution of severe contamination forming such surface texture was suggested.
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