Program SAFEGUARD:

Passive FT-IR ground-truth measurements

In addition to active FT-IR measurements during SAFEGUARD experiments, AeroSurvey also provides ground truth data derived from passively collected FT-IR spectra.  Most of these instances involve industrial collections in which it is difficult to make active measurements and the somewhat poorer sensitivity and accuracy of passive methods do not significantly affect the usefulness of the ground-truth data collected.  Below, we show a passive FT-IR spectrum of a plume exiting a stack from a nitric acid plant, as well as quantitative data derived from many such spectra.  The plume was used as a target during an industrial data collection experiment in 1999.

The single-beam spectrum below shows the infrared emission lines of ammonia atop the background infrared emission signal. 

The plot of concentration values in the target plume (red line below) was created from analysis of many passive spectra collected as the aircraft made one pass over the stack   The horizontal band superimposed on the red line represents one standard deviation in the data population.