Proceedings Article | 5 November 2020
KEYWORDS: Scattering, Atmospheric sensing, Atmospheric modeling, Atmospheric particles, Atmospheric optics, Remote sensing, Aerosols, Earth's atmosphere, Solar radiation
The solar spectrum of 400-2500nm wavelength is mostly used in optical remote sensing satellite for land observation. In this spectrum, the radiation received in the view field of satellite dominated by reflecting solar energy. This work analyzed the radiation transferring model of atmospheric scattering and absorption theoretically and simulated the effects on optical remote sensing of aerosol and water vapor experimentally. The theoretical radiation models of atmosphere scattering and absorption have been analyzed; the influencing processes of atmosphere scattering and absorption for remote sensing imaging chain have been simulated by atmospheric radiation transferring model. This work gives the impact mechanisms of atmospheric scattering and absorbing processes by tracing the radiation in the transferring chain from sun to land-surface and to satellite. Simulation experiments of aerosol absorbing and scattering effects on atmosphere path radiance and scattering transmittance and the effect of water vapor absorption on atmosphere transmittance have been made, including analyzing the effects of aerosol and water vapor in typical wavelengths of land observing satellite with three typical atmosphere models (mid-latitude summer continental model, mid-latitude winter continental model and 1976 US standard model). The results indicate that: 1) atmosphere aerosol scattering mainly affects the visible (VIS) solar spectrum, the effects becoming greater as wavelength being shorter thus caused the most significant influence on deep blue and blue bands, less effect on NIR and nearly no impacts on SWIR bands with wavelength longer than 2200nm. The atmosphere path radiance in SWIR is less than 1% of VIS, and the atmosphere scattering transmittance in SWIR is more than 4 times of VIS as the aerosol optical depth (AOD) increasing from 0.05 to 2. 2) Water vapor absorption mainly affects longer wavelength radiation, i.e. the near infrared (NIR) and infrared (IR) spectrum. Unlike aerosol effects, water vapor has more complex function in IR spectrum, there are several strong water vapor absorption peaks and atmosphere windows in NIR and SWIR, and the sensitivity of different absorption peaks are varied with the changing of water vapor content. Five IR bands, 865nm, 940nm, 1240nm, 1380nm and 1860nm, are involved to study the effects of water vapor on atmosphere transmittance. The atmosphere transmittance decreases from 0.97 to 0.2 in 940nm and 1240, and from 0.6 to almost 0 in 1380nm and 1860nm as the water vapor content increasing from 0.05 to 4.2 g/cm2, and 865nm is almost independent on the varying of water vapor. Image quality assessment experiments are implemented to study the degradation to image quality of optical remote sensing satellite caused by atmosphere absorbing and scattering effects. In assessment experiments, image sharpness is chosen as the quality parameters. Based on the comparisons of different atmospheric compositions correction in wavelengths of blue (490nm), green (560nm), red (665nm), NIR (965nm) and SWIR (1380nm) images of Landsat-8, the results show that aerosol has greater decreasing on image sharpness of blue band than others, and water vapor mainly degrades the image sharpness of NIR and SWIR bands. The result of image quality assessment experiments has verified the theoretical analysis.
