Inversion method of target gas cloud transmittance based on atmospheric profile synthesis background

The sky infrared background radiation varies greatly with spatial distribution and time. When Scanning Fourier Transform Infrared (FTIR) remote sensing imaging system scans the target gas cloud with the sky as the background, the background radiation corresponding to each scanned pixel is different, and the background does not have a constant baseline. It is extremely difficult to obtain the background spectrum of each pixel in real-time, which affects the inversion accuracy of the target gas cloud transmittance. An inversion method of target gas cloud transmittance based on atmospheric profile synthesis background is proposed. The temperature, humidity, pressure, and ozone profiles of the measured locations and the atmospheric model are used to generate the sky infrared background in order to solve the problem that it is difficult to measure the clean sky infrared background spectrum in the chemical industry park. This paper proposes that there is a continuous derivable relationship between the sky infrared background spectrum and the cosine of zenith angle at each wavenumber, so a small amount of sky infrared background spectrum with a zenith angle gradient can quickly generate sky infrared background spectrum at any elevation angle. The proposed method is verified by the Moderate Resolution Atmospheric Radiative Transfer Model (MODTRAN) software simulation and the remote sensing imaging experiment of SF6 gas. The proposed method can quickly generate the sky infrared background spectrum corresponding to any angle within the gradient elevation angle and accurately invert the target gas cloud transmittance at each pixel. The results show that the distribution trend of the column concentration of the SF6 gas cloud is consistent with the actual distribution, the correlation is 0.99979.