Abstract

Passive remote sensing of airborne chemicals at infrared wavelengths may be limited by temporal fluctuations in atmospheric brightness temperatures δT(�??t). Brightness temperatures in two infrared spectral bands were simultaneously measured on clear and cloudy days along three lines of sights. For time windows �??t < 3-5 s, δT(�??t) remained constant at the sensor noise level and rapidly increased as �??t increased. The fluctuation time scale for the cloudy day was longer than for the clear day. The long correlation time for T(t) limits the utility of signal averaging in improving detection signal-to-noise ratio (SNR). The simultaneous outputs of the two spectral channels during the clear day exhibited no spectral coherence at �??t < 3 s and limited coherence at �??t > 30 s. Measurements during the cloudy day were largely coherent. Consequently, band-by-band subtraction may have limited benefits.

© 2005 Optical Society of America

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Air monitoring by spectroscopic techniqu (1)

P. L. Hanst and S. T. Hanst, �??Gas measurement in the fundamental infrared region,�?? in Air monitoring by spectroscopic techniques, M. W. Sigrist, ed. (Wiley, New York, NY, 1994).

Appl. Opt. (8)

Encyclopedia of analytical chemistry (1)

D. W. T. Griffith and I. M. Jamie, �??Fourier transform infrared spectrometry in atmospheric and trace gas analysis,�?? in Encyclopedia of analytical chemistry, R. A. Meyers, ed. (Wiley, Chichester, England, 2000).

J. Opt. Soc. Am. A. (1)

Ancellet, G. M. and R. T. Menzies, �??Atmospheric correlation-time measurements and the effects on coherent Doppler lidar,�?? J. Opt. Soc. Am. A. 4, 367-373 (1987).

Opt. Eng. (2)

S. Holland, R. Krauss, G. Laufer, "Demonstration of an uncooled LiTaO3-detector-based differential absorption radiometer for remote sensing of chemical effluents," Opt. Eng. 43, 2303-2311 (2004).
[CrossRef]

S. K. Holland, R. H. Krauss, G. Laufer, The effect of temperature on passive remote sensing of chemicals by differential absorption radiometry, to be published in Opt. Eng. (October 2005).

Opt. Express (1)

Opt. Lett. (1)

Other (5)

R. R. Beland, �??Propagation through atmospheric optical turbulence,�?? Ch. 2, Vol. 2, The infrared and electrooptical system handbook, ed. F. G. Smith SPIE Press, Bellingham, WA, USA, (1993).

R. E. Hufnagel, �??Propagation through atmospheric turbulence,�?? Ch. 6 The infrared handbook revised edition, ed. W. L. Wolfe and G. J. Zissis, The Infrared Information Analysis (IRIA) Center, Environmental Research Insitute of Michigan, USA (1985).

PcModWin 4.0 , MODTRAN atmospheric radiative transfer code, Ontar Corporation, North Andover, MA (2002).

S. M. Kay, Modern Spectral Estimation, Ch. 4, P T R Prentice Hall, Englewood Cliffs, New Jersey (1988).

A Papoulis and S. U. Pillali, Probability, random variables and stochastic processes, Ch. 12, McGraw-Hill, New York, 4th edition (2002).

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