Electro-optical sensors measure energy transmitted by lasers spaced about a region’s periphery. Both the lasers and sensors are tuned to infrared frequencies at which air pollutants strongly absorb electromagnetic energy. The sensor measurements are processed using an algorithm derived from the Radon transform. The result is an estimate of air pollutant density throughout the region that has been smoothed to minimize effects due to background sunlight fluctuations, laser fading and phase scintillation, and intrinsic sensor noise. Good agreement is found between a theoretical analysis of performance limitations and computer simulation results
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(1) NO2 has an absorption coefficient one-third that of NO at 5.31 μm, In order to estimate the amount of each species, measurements must be performed at another frequency. See last section for some additional comments. (Source: unpublished work performed at Bell Laboratories.)
(2) Absorption due to water vapor is negligible at these frequencies (Source: unpublished work performed at Bell Laboratories.)
(3) NO2, PAN, and other chemical species have been ignored here, although they do contribute significantly to air pollution.
E. D. Hinkley, “Bistatic Monitoring of Gaseous Pollutants with Tunable Semiconductor Lasers,” Fig. 20, in Proceedings of the Symposium on Remote Sensing of Environmental Air Pollutants, Cleveland, Ohio, March 7, 1974 (unpublished).
TABLE II
Estimated error in reconstructing an impulse using Eq. (2.16)
(1) NO2 has an absorption coefficient one-third that of NO at 5.31 μm, In order to estimate the amount of each species, measurements must be performed at another frequency. See last section for some additional comments. (Source: unpublished work performed at Bell Laboratories.)
(2) Absorption due to water vapor is negligible at these frequencies (Source: unpublished work performed at Bell Laboratories.)
(3) NO2, PAN, and other chemical species have been ignored here, although they do contribute significantly to air pollution.
E. D. Hinkley, “Bistatic Monitoring of Gaseous Pollutants with Tunable Semiconductor Lasers,” Fig. 20, in Proceedings of the Symposium on Remote Sensing of Environmental Air Pollutants, Cleveland, Ohio, March 7, 1974 (unpublished).
TABLE II
Estimated error in reconstructing an impulse using Eq. (2.16)