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.
