Detection of atmospheric pollutants by direct analysis of passive Fourier transform infrared interferograms

Methodology is developed that allows interferograms from a passive Fourier transform infrared (FTIR) spectrometer to be analyzed directly. With a digital filtering approach, a set of generalized procedures is developed for real-time monitoring of atmospheric pollutants. These procedures allow the spectrometer to be mobile, overcoming problems associated with changing spectral backgrounds and with severe data processing requirements. The methodology allows customized digital filters to be developed that remove information from the interferogram except that associated with frequencies characteristic of a target chemical species of interest. To test the methodology, a filter is derived that is specific of for SF/sub 6/. With the use of a passive FTIR instrument mounted in a helicopter, several passes are made by a ground source of SF/sub 6/, thereby simulating the action of a mobile pollution monitoring system. Interferograms collected during this experiment are used to evaluate the computed filter.