<title>Gaseous emanation detection algorithm using a Fourier transform interferometer operating in differential mode</title>

Abstract

Enactment of the Clean Air Act Amendments of 1990 has resulted in an increased ambient air monitoring needs for industry, some of which may be met efficiently using open- path optical remote sensing (ORS) techniques. Among the most promising of these techniques, we note the Fourier transform spectrometry (FTS). This technique is well suited for the detection of organic and inorganic chemicals since most of them have characteristic absorption bands in one or both of the IR atmospheric window regions. The need for reliable atmospheric pollution monitoring has motivated the development of a number of new chemical analysis approaches. This paper presents an approach for the spectral remote sensing of gaseous emanations from chemical agents, based on the measurements of their weak emission spectra via a passive IR FTS sensor. The method is implemented using such a sensor operating in differential mode between the two inputs, allowing the background to be optically subtracted. A specific algorithm has been developed jointly by Bomem and the Defence Research Establishment of Valcartier to take advantage of this particular setup and allow identification of trace gases in real time. A software research tool named GASEM implements this algorithm and is used with CATSI, a double-beam remote sensing interferometer operating in differential mode in the 3.5-17 micrometers spectral range.