大气红外辐射及消光特性实测研究

Measurement of Atmospheric Infrared Radiance and Extinction Characteristics

应大口径红外望远镜选址需求,研制了一台红外辐射测量设备,对丽江天文观测站及澄江M′波段(4.605~4.755μm)大气红外辐射与消光特性进行了实测。用Allan方差法和大气辐射传输方程分别对大气辐射的时间和空间变化数据进行了分析,讨论了辐射时空变化对红外天文观测的影响。结果表明,低频区的辐射涨落较大,Allan方差随积分时间呈指数增加,丽江和澄江的Allan方差拟合参数分别为0.794和1.238。从天顶到60°天顶角,丽江和澄江站的辐射亮度分别增大了68%和72%,透过率分别降至0.46和0.52;红外天文观测需斩波,在丽江站,探测器单像元、2×2Binning、4×4Binning最佳斩波频率分别为0.030,0.070,0.144 Hz。实测所得Allan方差、大气消光、最佳斩波频率可用于指导大口径红外望远镜的选址及设计。

Based on the demand of site selection for large infrared telescopes,an infrared radiation measurement device is developed to measure the M′ band（4.605-4.755μm）atmospheric infrared radiance and extinction characteristics at Lijiang and Chengjiang observatories.The data of temporal and spatial variations of atmospheric radiation is analyzed by Allan variance method and atmospheric radiative transfer equation,and the influence of temporal-spatial variation of radiation on infrared astronomical observation is discussed.The results show that the radiative fluctuation in the low frequency region is large,Allan variance increases exponentially with integration time,and the fitting parameters of Allan variance for Lijiang and Chengjiang observatories are 0.794 and 1.238,respectively.From zenith to 60°zenith angle,radiance of Lijiang and Chengjiang observatories increases by 68%and72%,and the transmittance decreases to 0.46 and 0.52,respectively.Infrared astronomical observation needs chopping,and the best chopping frequencies at Lijiang observatory of the single pixel,2×2 Binning and 4×4 Binning modes are 0.030,0.070,0.144 Hz,respectively.Allan variance,atmospheric extinction,and the best chopping frequency can be used to guide the site selection and design of large infrared telescopes.