High-Resolution Scattered Radiation Measurement in Ultraviolet Band Based on Spatial Heterodyne Spectroscopy Technique
FANG Xue-jing1, 2, 3, LUO Hai-yan1, 3, SHI Hai-liang1, 3, LI Zhi-wei1, 3, HU Guang-xiao1, 2, 3, JIN Wei1, 2, 3,ZHANG Ji-cheng1, 2, 3, XIONG Wei1, 2, 3*
1. Anhui Institute of Optics and Fine Mechanics，Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
2. University of Science and Technology of China, Hefei 230026, China
3. Key Laboratory of Optical Calibration and Characterization of Chinese Academy of Sciences, Hefei 230031, China
Abstract：The hydroxyl (OH) radical is the most important oxidizing agent in the photochemical reactions which helps to understand the atmospheric components and photochemistry events in mesosphere. OH radical’s solar resonance fluorescence A2Σ＋-X2Π（0，0） is the excited emergent light by solar radiation around 308 nm. Hyper-spectral Resolution Spectrometer for Mesospheric OH Radical is developed to detect OH ultraviolet solar resonance fluorescence in mesosphere and separate target signal from complex background signal. The spectral range is 308.2~309.8 nm and its spectral resolution is 0.008 25 nm. Limb observation mode detects atmospheric scattering signal which consists of atmospheric molecules, aerosols and cloud scattered by solar energy. Hyper-spectral Resolution Spectrometer for Mesospheric OH Radical is based on Spatial Heterodyne Spectroscopy technique. SHS technique receives rather high spectral resolution around Littrow wavelength and is applicable to fine detection of atmospheric components. Adding cylindrical lens front or behind the optical system results in several split-fields of view. Each split corresponds line of detector imaging plane. Limb observation can obtain limb-scattered signal at different height simultaneously using layered imaging in spatial dimension with SHS technique rather than traditional limb detector scanning at different height. In order to validate detection ability and sensitivity to observation geometry of Hyper-spectral Resolution Spectrometer for Mesospheric OH Radical , a ground-based limb observation experiment is built up to detect atmospheric limb-scattered signal around 308 nm. Simulating limb mode geometry in a clear sky, limb-scattered radiation is detected in an open place. Interferogram error correction and spectrum restoration are needed due to the fact that the instrument is based on SHS. Spectrum restoration and calibration are done to a serial interferogram data at 10 min interval in a period of observation time to obtain final spectrum. The source of scattered radiation is the atmospheric molecule’s scattering of sunlight, so the spectrum should contain high-resolution features information of solar spectrum. Choose 3 feature windows from high-resolution solar spectrum and analyze correspond band in observation spectrum. It turns out that the feature windows match completely. The results can validate detection ability and fine spectrum extracting ability of Hyper-spectral Resolution Spectrometer for Mesospheric OH Radical. Radiative transfer model is set using real time aerosol optical thickness measured by solar radiometer, real time solar zenith and azimuth angle and atmospheric profiles with corresponding date, longitude and latitude. A comparison is taken between simulation spectrum and observation spectrum. Their residual is rather small. The residual between them due to the mismatch between atmospheric parameters setting and actual situation. Real time temperature and pressure profiles are considered to bring in radiative transfer model in the future. These results validate limb-scattered radiation detection ability and fine spectrum extracting ability and sensitivity to observation geometry of Hyper-spectral Resolution Spectrometer for Mesospheric OH Radical. The experiment results not only validate the feasibility in detecting multi-band and broad-band limb-scattered signal and OH target signal on orbit, but also provide theoretical and experimental foundation for orbital limb-scattering signal detection.
方雪静，罗海燕，施海亮，李志伟，胡广骁，金 伟，张纪承，熊 伟. 利用空间外差光谱技术进行紫外高分辨率大气散射信号探测[J]. 光谱学与光谱分析, 2019, 39(02): 357-362.
FANG Xue-jing, LUO Hai-yan, SHI Hai-liang, LI Zhi-wei, HU Guang-xiao, JIN Wei,ZHANG Ji-cheng, XIONG Wei. High-Resolution Scattered Radiation Measurement in Ultraviolet Band Based on Spatial Heterodyne Spectroscopy Technique. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(02): 357-362.
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