31.1 How does remote sensing of chemical pollutants work?
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This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.
31.1 How does remote sensing of chemical pollutants work?
The are several techniques, but the one of most interest to the public is
the system being used to identify grossly polluting vehicles. The system
consists of an infra-red source on one side of the road, and a detector
system on the other. The collimated beam of IR is directed at a gas filter
radiometer equipped with two liquid-nitrogen-cooled indium antimide
photovoltaic detectors. The beam is split, and passes through a 4.3um
bandpass filter to isolate the CO2 spectral region, a 4.6um filter to
isolates the CO region, and a third filter to isolate the HC region.
A non-absorbing region is also used to compensate for signal strength.
There are various specific enhancements, such as the spinning gas-filter
correlation cell in the University of Denver FEAT ( Fuel Efficiency
Automobile Test ) system used to cost-effectively identify grossly-polluting
vehicles [1]. "Optical remote sensing for air pollutants - review " by
M.Simonds et al [2], provides a good introduction to the diverse range of
instruments used for remote sensing of pollutants.
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