不依赖标准星的红外大气消光测量方法研究

Infrared observation has unique advantages in astronomical research such as cool celestial objects, extrasolar planets, the temperature minimum region of the quiet solar atmosphere. Many large infrared telescopes have been built in the world, but the sensitivity of large aperture telescopes is limited by the infrared atmospheric extinction at the site. Therefore, the infrared atmospheric extinction is an important indicator for evaluating astronomical sites and the scientific value of large infrared telescopes.. This project is based on the requirement of measuring infrared atmospheric extinction by sites survey for large aperture infrared telescopes, and carrying out the research of the measurement method independent of standard stars of infrared atmospheric extinction. Based on the atmospheric radiative transfer equation, establishing a mathematical model for the convenient measurement of infrared atmospheric extinction, the inversion of atmospheric extinction by measuring infrared radiation from different zenith angle, this method can overcome the shortcomings such as not suitable for small diameter equipment, low signal-noise-ratio, low time resolution of the measurement method depending on standard stars of the atmospheric extinction. The contents of research include the establishment and application of the model, the mode and strategy of observation, the actual measurements and the error analysis. Research to be carried out on the applicability of the model, the influence of the sun and clouds, and accurately and synchronously measuring the atmospheric radiation and zenith angle, and verifying the accuracy of the results. Accurately measuring the infrared atmospheric extinction and time variation of alternative astronomical sites with the small diameter equipment can provide guidance for the site survey and accumulate experience for the ground-based infrared astronomical observation.

红外观测在低温天体、系外行星、太阳大气温度极小区等天文研究中有独特优势，国内外纷纷建造地基大口径红外望远镜，但台址红外大气消光限制了大口径望远镜灵敏度优势。红外大气消光是评价台址及地基红外大望远镜科学价值的重要指标。. 本项目立足于红外大望远镜选址对测量红外大气消光的需求，研究不依赖标准星的红外大气消光测量方法。基于大气辐射传输方程，建立了便于实测红外大气消光的数学模型，扫描测量不同天顶角的红外大气辐射来反演红外大气消光，能克服依赖标准星的红外大气消光测量法不适合小口径设备、信噪比低、时间分辨率低的不足。研究内容包括模型建立及应用、观测模式及策略、实测及误差分析。针对实测中模型适用性、太阳和云的影响、准确并同步测量大气辐射和天顶角、结果准确性验证等问题开展研究。项目可实现小口径设备对备选台址红外大气消光及时变特性的准确测量，为台址评价及选址决策提供指导，为地基红外天文观测积累经验。

红外大气消光是评价台址红外观测条件的重要指标。本项目从地基大口径红外望远镜的建设需求出发，开展不依赖标准星的红外大气消光测量方法研究，为地基红外望远镜建设及选址决策提供指导，为地基红外天文观测积累经验。研究了红外大气消光测量模型适用性，发展了一套适用光学薄和光学厚两种大气条件的测量方法；在红外大气消光的观测模式研究中，升级改造了已有设备，实现了不同观测模式切换以及大气辐射和消光的快速测量；运用自建的分层大气模型和大气辐射传输仿真软件对阿里等典型台址大气消光进行计算并对比实测结果，验证了本项目方法的准确性；在仪器噪声检测及误差分析过程中发展了一套噪声等效温差测试装置及方法；以阿里、稻城等优秀红外台址大气辐射与消光的初步实测数据为基础，建立了一套便捷、实用的望远镜灵敏度分析模型，综合分析了望远镜及仪器、红外探测器、台址大气对大口径红外望远镜观测灵敏度的影响，结果表明，要充分发挥台址优势，需严格控制红外探测器读出噪声、望远镜及仪器热辐射，以阿里为例，探测器读出噪声应小于200e-，如果深度制冷终端仪器，主副镜发射率应小于0.017。项目执行期间，共毕业1名博士生和2名硕士生；共发表了4篇学术论文，公开了2项发明专利，已授权1项。本项目解决了大气红外辐射与消光测量中的若干技术方法问题，为红外台址评价储备了数据及技术；前瞻性地研究了地基红外观测灵敏度及其影响因素等问题，为望远镜发射率控制、终端仪器制冷、红外探测器选择等决策工作提供了指导及技术支持。