15 December 2000 Detection of cryogenic water ice contaminants and the IR AI&T environment
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Abstract
Several remote sensing/infrared space surveillance programs in the midst of assembly, integration and test have recently experienced delays when water vapor was deposited as ice on cold surfaces in a sensor under test or calibration. When these surfaces were at critical locations, the sensitivity or response of the sensor decreased significantly because the ice absorbed the incoming signal. The source of water vapor could be from a chamber leak or outgassing from the sensor system or the vacuum chamber itself. In order to quantify the effects of ice deposits on signals in various spectral bands, published optical constants for amorphous and crystalline water ice have been used to calculate the transmission of water ice films as a function of wavelength from 1 to 20 microns. The results are presented in two ways: spectra of the physical thickness of a layer of ice whose absorption optical depth is unity, and transmission spectra for several characteristic layer thicknesses. These tools can be used in estimating the amount of ice - and by inference water vapor - present in the system. Related calculations can also be used to assess the probability that a given hardware setup or resulting data set is showing signs of degradation of response due to ice absorption, and the implications for those trying to interpret the results.
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David K. Lynch, Ray W. Russell, "Detection of cryogenic water ice contaminants and the IR AI&T environment", Proc. SPIE 4130, Infrared Technology and Applications XXVI, (15 December 2000); doi: 10.1117/12.409852; https://doi.org/10.1117/12.409852
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