Application Research of Airborne Optical Fiber Imaging Differential
Absorption Spectrometer in Measuring Regional Air Pollution
ZHANG Xiao-li1, WANG Yu1, 2*, XI Liang2, ZHOU Hai-jin2, CHANG Zhen2, SI Fu-qi2
1. Institutes of Physical Science and Information Technology, Anhui University, Hefei 230031, China
2. Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics，Chinese Academy of Sciences, Hefei 230031, China
Abstract：Air pollution in China presents regional and complex characteristics. Carrying out stereo monitoring of the regional distribution of polluted gases can help us understand the status quo of the atmospheric environment in a timely manner, study and analyze various factors affecting air quality, and guide air pollution control measures. The airborne imaging differential optical absorption spectroscopy is one of the effective remote sensing methods for the regional distribution of polluted gases. This technology has a large observation area and a high coverage rate, which can provide a detailed regional distribution of polluted gases and realize the visual detection of pollution distribution and transmission. In the past, the airborne imaging differential absorption spectrometer used an overall design that needed to occupy the optical observation window of the aircraft. The optical fiber imaging differential absorption spectrometer introduced in this paper adopts the optical fiber beam transmission method, which needs minimal requirements during installation, greatly facilitates the installation and debugging on the aircraft, and meets the requirements of airworthiness equipment certification. This system uses a special multi-core fiber bundle combined with a Littow-offner structure spectral imaging system, which has the advantages of high spectral imaging resolution, large field of view, and compact structure. The paper introduces the equipment performance parameters in detail, and the verification experiment is carried out using the system around Wuhu City. A data processing algorithm is proposed for the optical fiber imaging differential absorption spectrometer in the application process. In this experiment, the slanted column concentration of polluting gas is obtained by retrieving the collected scattered solar light, and the air quality factor is calculated using the atmospheric radiative transmission model. Then, convert the slanted column concentration into a path-independent vertical column concentration. Finally, the results are displayed on the map combined with the aircraft angles and positions. This equipment can quickly obtain the concentration distribution of NO2 and SO2 over Wuhu City and its surrounding areas realize the rapid location of pollution sources and analyze the transmission process. According to the results, there are 4 high-value points of NO2 vertical column concentration and 2 high-value points of SO2 vertical column concentration in the experimental area. According to the map, there are industrials around the high-value points, and the results are consistent with the actual situation. Finally, we evaluated the precision between satellite data and airborne data. They have a positive correlation with a correlation coefficient of 0.77. The results show that the scheme of optical fiber imaging differential absorption spectrometer is verified, which can provide a basis popularising air pollution gas remote sensing technology and compensate for the shortage on the spatial scale in ground station and the shortage on the time scale in satellite test.
Key words：Airborne;Imaging differential absorption spectrometer;NO2;SO2;Two-dimensional distribution of polluted gases
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