大气背景对中红外波段太阳观测影响的模拟与实测方法研究

Solar observation and research at Mid-IR will be the main trend in the future. However, the complicated atmospheric backgrounds which are composed of the atmospheric radiance and molecule absorption spectra will seriously influence signal-to-noise of the observation, the accuracy of the magnetic field measurement and spectrum measurement. The purpose of this project is to simulate the local atmospheric background properties as a spectral, temporal and spatial distribution function by modern atmospheric software. And based on the results of simulation, we try to design a measurement method of the atmospheric backgrounds in the waveband of 8-14μm, which is proper to be carried out in the field. And we are going to develop a compact observational experiment set with the aids of optical design tools and stray light analysis software. Using this experiment set, we can obtain the field observational data at the suitable candidate locations. Comparative analysis of the results of field measurements and theoretical simulation will be made, and then by applying the measured results, the influence of the atmospheric backgrounds on the solar observation in the Mid-IR wave band will be evaluated. The results of this project will provide the development of the future Mid-IR solar telescopes with those measured data, and will accumulate theoretical and technical experience for the solar observation site selection in the Mid-IR waveband.

中红外波段观测是未来太阳观测和研究发展的必然方向。然而中红外波段大气辐射与密集分布的分子吸收带以及大气消光等构成极为复杂的光谱观测背景，这将对观测信噪比、磁场测量精度与光谱研究的准确性等方面造成严重影响。本项目旨在应用大气软件进行模拟计算的方法，研究中红外波段局地大气背景光谱分布、空间分布和时间分布等特性；并以模拟计算结果为依据，研究适于中红外8 - 14微米波段大气背景实地测量方法；应用光学设计与杂散光分析软件设计并研制小型实验观测系统；对选址工作初步锁定的候选台址进行实地观测，获得大气背景实地观测数据；对比分析实测结果与理论模拟结果，应用实测结果评估中红外大气背景对太阳观测的影响；为未来望远镜设计提供相关的实测依据；并为太阳台址选择工作积累中红外波段的理论和技术基础。

中红外波段是未来太阳物理研究发展的必然方向。然而在中红外波段太阳辐射强度迅速下降的同时，大气辐射与密集分布的分子吸收带构成了极为复杂的光谱观测背景，将严重影响信噪比和测量精度。因此大气背景辐射特性和传输特性是未来大型地基红外观测设备站址选择必须考虑的重要内容。本项目针对这一需求，我们发展了一套实地测量方案，采用红外傅立叶变换光谱仪，对川、滇、藏以及青海等地区的多个备选站址进行实地测量。获得了各地3~14微米中红外波段的太阳直射辐射强度及大气背景辐射的实测数据，光谱分辨率达到1cm-1。同时结合各地的气象数据，采用大气仿真软件进行模拟计算，并与实测数据进行比较分析，结果显示两者趋势基本符合，并且得出结论，大气中水气含量是影响中红外波段透过率以及大气背景的敏感参量。本项目研究为中红外观测台址选定以及为望远镜及后端仪器设备的设计等方面提供有力的实测数据支持。