Radiation effects on contaminants from the outgassing of silastic 140 RTV

Exposure of the volatile condensable material (VCM) from Silastic 140 RTV adhesive sealant to 147. 0-nm radiation, simulating the space radiation environment in synchronous earth orbits, induces absorption of visible light by the VCM. This results in an increase in the absorptance of coated optical elements, such as solar cell cover glasses and second-surface mirrors for thermal control. A contaminant thickness of 0.1 micron or more could result in a change in solar absorptance of the second-surface mirrors from 0.06 to approximately 0.16 in a period of about 1.5 years in space. Calculations indicated that the VCM thickness would have to be less than approximately 0.005 micron to keep the change in solar absorptance 0.01 for a 3-year mission.