Retrieval algorithm of quantitative analysis of passive Fourier transform infrared (FTRD) remote sensing measurements of chemical gas cloud from measuring the transmissivity by passive remote Fourier transform infrared
Key Laboratory of Environmental Optics & Technology, Chinese Academy of Sciences, Hefei 230031, China; Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Abstract Passive Fourier transform infrared (FTIR) remote sensing measurement of chemical gas cloud is a vital technology. It takes an important part in many fields for the detection of released gases. The principle of concentration measurement is based on the Beer--Lambert law. Unlike the active measurement, for the passive remote sensing, in most cases, the difference between the temperature of the gas cloud and the brightness temperature of the background is usually a few kelvins. The gas cloud emission is almost equal to the background emission, thereby the emission of the gas cloud cannot be ignored. The concentration retrieval algorithm is quite different from the active measurement. In this paper, the concentration retrieval algorithm for the passive FTIR remote measurement of gas cloud is presented in detail, which involves radiative transfer model, radiometric calibration, absorption coefficient calculation, et al. The background spectrum has a broad feature, which is a slowly varying function of frequency. In this paper, the background spectrum is fitted with a polynomial by using the Levenberg--Marquardt method which is a kind of nonlinear least squares fitting algorithm. No background spectra are required. Thus, this method allows mobile, real-time and fast measurements of gas clouds.
Received: 08 April 2008
Revised: 16 May 2008
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant No 083H311501) and the
National High Technology Research and Development Program of China
(Grant No 073H3f1514).
Cite this article:
Liu Zhi-Ming (刘志明), Liu Wen-Qing (刘文清), Gao Min-Guang (高闽光), Tong Jing-Jing (童晶晶), Zhang Tian-Shu (张天舒), Xu Liang (徐 亮), Wei Xiu-Li (魏秀丽) Retrieval algorithm of quantitative analysis of passive Fourier transform infrared (FTRD) remote sensing measurements of chemical gas cloud from measuring the transmissivity by passive remote Fourier transform infrared 2008 Chin. Phys. B 17 4184
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