Effects of atmospheric water vapor on detection performance of a linear variable filter based instrument

Abstract

Linear variable filter design and fabrication for LWIR is now commercially available for use in the development of airborne reconnaissance or surveillance systems. The linear variable filter is attached directly to the cold shield of the focal plane array. The resulting compact spectrometer assemblies are completely contained in the Dewar system. This approach eliminates many of the wavelength calibration problems associated with current prism and grating systems and also facilitates the cost effective design and fabrication of aerial sensing systems for specific applications. An optimal 32 band linear-variablefilter- based system for detecting and discriminating a set of 11 chemicals representing a high probability of occurrence during a typical emergency response chemical incident was determined in a companion paper entitled "Linear Variable Filter Optimization for Emergency Response Chemical Detection and Discrimination". This paper addresses the effects of atmospheric water vapor on the performance of this optimal 32 band linear-variable-filter-based system. This paper also determines at what increased concentration levels above the optimal system design goal of 30 ppm-m can detection and discrimination of these 11 chemicals be achieved in realistic but imperfect atmospheric water vapor removal scenarios.