Transmittance Simulation Calculation Based on 3D Ray Tracing and HITRAN Database
SUN Ming-chen1,2, WU Xiao-cheng1*, GONG Xiao-yan1, HU Xiong1
1. National Space Science Center, Chinese Academy of Sciences, Beijing 100190，China
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：The 3D ray tracing method is used to simulate the transmission of oxygen in the atmosphere from ground to 110 km in the stellar occultation technique. The carrier frequency is 3.53×1015 Hz, the Earth is ellipsoid, and the model is the neutral atmosphere. It is known that the three-dimensional position coordinates of target stellar and low-orbit satellite orbit data in the earth-solid system. And then the high resolution of oxygen molecular absorption line parameters in the HITRAN database are used, including the absorption line intensity, low-level energy, etc., to calculate the transmittance of oxygen molecules in the near-infrared absorption band A. In addition, taking Sirius’ infrared spectrum as the original receiving spectrum, that is, removing the absorption and scattering of the Earth’s atmosphere, the spectral energy decreases as the wavelength increases. The characteristic absorption lines of oxygen are selected at 760 and 762 nm, and the atmospheric transmittance of the line position is calculated as a function of height. The signal-to-noise ratio of the received spectrum is calculated by transmittance to guide the instrument design. In addition, due to atmospheric refraction, the resulting transmittance must be corrected for refraction. According to the simulation calculation, the atmospheric transmittance of three heights of 80, 100 and 110 km is calculated by using the near-infrared band of 755~774 nm, approaching 1 as the height increases gradually. Compared with 0.2 nm resolution, the atmospheric transmittance obtained under 0.1 nm resolution range is larger, is 0.28~1, the transmittance at 110 km is 0.987, and the accuracy of the detection can be a small one. The transmittance caused by atmospheric refraction above 60 km is equal to 1. Therefore, the influence of atmospheric refraction on atmospheric transmittance can be neglected above 60 km, so no refraction correction is required above 60 km. The signal-to-noise ratio is greater than 100 on the characteristic absorption lines at 760 and 762 nm. When the resolution is 0.1 nm, the value of the spectral intensity signal-to-noise ratio is smaller, indicating that the absorption of oxygen by the spectrum is strong. The amount of change in the number of photons obtained under the two resolution conditions is not much different and is greater than one. Finally, based on the above results, parameters such as the telescope, CCD, grating resolution, and integration time canconfirm. The inversion algorithm used to study and test the stellar occultation to form a miniaturized instrument that detects the change in the density of oxygen from the ground to the height of 110 km, and can also analyze the detection error in advance.
Key words：Stellar occultation; Three-dimensional ray tracing; HITRAN; Near infrared; Transmittance
孙明晨，吴小成, 宫晓艳，胡 雄. 基于三维射线追踪和HITRAN数据库的透过率仿真计算[J]. 光谱学与光谱分析, 2020, 40(07): 2092-2097.
SUN Ming-chen, WU Xiao-cheng, GONG Xiao-yan, HU Xiong. Transmittance Simulation Calculation Based on 3D Ray Tracing and HITRAN Database. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(07): 2092-2097.
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