Abstract
The presence of propagated molecular gas around satellites is one of the most probable causes of optical degradations appeared on optical sensors equipped on the satellites. In order to evaluate transmittance degradation with various kinds of gases under different temperature and vacuum conditions, we built up the measurement systems. The main purpose of our study is to evaluate the variation of transmittance due to gas adsorption by making a specific, single component gas of high purity adhere to a glass material. As a result, the gases which are largely responsible for transmittance changes in the visible and near-infrared region can be identified. In our system, an optical glass, the site of adsorption, is set inside a cryostat and then a certain amount of molecular gas is injected. The amount of injected gas adsorption onto the optical surface is controlled by adjusting the sample surface temperature (150 K≤423K). In order to the wide wavelength coverage of earth observing sensors, two kinds of measurement systems were manufactured. The one for the UV to SWIR observation covers the wavelength from 350 nm to 2.5μm. The measurement accuracy of the UV-VISUAL-SWIR system is about 0.2%. The other for infrared observation covers from 2μm to 20μm. The measurement accuracy of the infrared system is about 1.6%. It turned out that our measurement systems have enough accuracies for evaluating the influence of gas contamination quantitatively.
