Remote sensing of chemical vapours by differential FTIR radiometry.

This paper presents a novel method for the passive remote sensing of chemical vapours by differential radiometry. The originality of the method lies in the use of a double-input beam Fourier-transform infrared (FTIR) spectrometer optimized for optical subtraction. A description of the interferometer (compact atmospheric sounding interferometer (CATSI)) is given along with the detection algorithm (gaseous emission monitoring algorithm (GASEM)) that controls the interferometer data acquisition and performs the on-line monitoring of chemical vapour parameters. The differential detection method has been successfully tested for several chemical vapours over distances of several hundred metres during open-air experiments held at Defence Research and Development Canada (DRDC). Valcartier and Ft Riley, Kansas. In particular. the detection method has been used to map the integrated concentration (column amount) and the temperature of a plume of methanol vapour. In this case, the uncertainties in the methanol plume parameters have been estimated to he of the order of 15.30% for the column amount. and 2.5 K for the gas temperature, which represents an acceptable result for this type of passive remote sensing. The technique has been applied to ammonia vapours and binary mixtures of the two gases as well. [ABSTRACT FROM AUTHOR]