大气红外透过率测量

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	大气红外透过率测量
其他题名	Atmospheric Infrared Transmittance Measurement
	陈双远
学位类型	硕士
导师	许方宇
	2019-07-01
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	天文技术与方法
关键词	大气透过率大气辐射测量辐射定标误差分析光学厚度
摘要	大气透过率和大气红外辐射作为地基空间目标探测、地基空间遥感、天文研究等领域的重要研究内容，红外探测系统接收目标辐射的能力与大气透过率和大气背景辐射限直接相关，其中，大气背景辐射限的强弱还决定了红外探测系统的极限灵敏度，将影响系统设计；红外天文研究中，它们也是反映天文台站红外观测性能优劣与否的重要指标。为此研究大气红外透过特性和大气红外辐射特性具有重要意义。地基红外天文观测，大气红外辐射背景不可忽略，须掌握其特性与变化规律；为此设计了一套中红外大气辐射测量系统。使用该系统尝试测量大气红外辐射的过程中，发现仪器辐射很强，大气辐射却很弱，强弱两种辐射信号完全耦合，仪器辐射这个背景信号将大大占用红外探测器的满阱电子数，降低系统动态范围；仪器辐射还随环境温度的变化而变化。这些都导致系统测量大气辐射的精度很低，为了提高测量精度，提高系统的动态范围，剥离仪器辐射与大气辐射信号，仔细研究了系统的定标方法。使用三元模型定标法对系统定标，并对整个望远镜系统进行稳恒的低温制冷和温控，通过这些关键手段，大幅提高了系统的稳定性，最终实现了对大气红外辐射的高精度测量。在实现了大气红外辐射高精度测量的基础之上，通过扫描测量不同天顶角的大气红外辐射亮度，再基于辐射传输方程的解，拟合辐射亮度随天顶角的变化，可得到测量波段内的平均大气透过率。据此，利用上述测量系统对阿里观测站、德令哈观测站和怀柔观测站M’波段（4.605~4.755 μm）内的平均大气透过率进行了实测。测量结果表明，在M’波段内阿里、德令哈、怀柔三地天顶平均大气透过率依次递减，天顶平均透过率的加权平均值依次为0.805、0.758、0.650。三地大气红外透过率均有起伏；怀柔的起伏量小，仅0.073，其透过率变化在三地当中最为稳定；阿里的透过率起伏也不大为0.081；德令哈的起伏相对要大很多，起伏达到0.250，表明其透过率很不稳定。透过率起伏与透过率高低无关，透过率低的地方也可能比较稳定，但相比之下在阿里进行红外天文观测效果最佳。作为比较，用MODTRAN软件模拟的三地平均透过率分别为0.846、0.794、0.623，软件模拟的结果基本能够与某一时刻的实测结果相对应，说明该方法测量的透过率结果可靠。该透过率测量方法不需要获取复杂的大气气象参数，相对简捷，便于在天文选址阶段对各址点大气的红外透过率进行一般评估。该透过率测量方法是通过测量各天顶角下的大气红外辐射亮度间接得到天顶平均透过率，因此系统对大气红外辐射亮度测量结果的不确定度对最终拟合的透过率结果有影响。所以在分析得到平均大气透过率的理论误差过程中，首先分析了大气红外辐射的测量误差，包括随机误差、定标误差和外推误差。结果表明该系统在定标区间内的辐射测量误差主要是定标误差和随机误差，两者分别为2.4719%、0.0790%；合成误差为2.4732%。当用该系统测量大气红外辐射时，对大多数优良的天文台站而言，大气辐射强度远低于定标时的辐射强度，不得已需要进行外推测量；对外推测量误差的估计结果表明，外推测量可能导致较高测量误差。因此，为提高大气红外辐射测量精度，更低辐射强度的标准辐射源不可或缺。综合考虑各类误差后，得到系统进行大气辐射测量的理论误差为12.64%。通过误差传递的分析方法得到天顶平均大气透过率理论误差小于10%。
其他摘要	Atmospheric transmittance and atmospheric infrared radiation are important contents in the fields of research ground-based space target detection, ground-based space remote sensing, and astronomical research and other fields. The ability of infrared detection system to receive target radiation is directly related to the atmospheric transmissivity and the atmospheric background radiation limit. The intensity of the atmospheric background radiation determines the sensitivity limit of the infrared detection system, which will direct affects the system design. In infrared astronomical research, they are also important index to reflect the astronomical observing conditions and performances of the observatory stations. Therefore, it is great significant for studying the atmosphere infrared transmission characteristics and the infrared radiation characteristics.Ground-based infrared astronomical observation, the background of atmospheric infrared radiation can not be neglected, and its characteristics and changing laws must be mastered. A measurement system of mid-infrared atmospheric radiation is designed for this purpose. In the process of using this system try to measure atmospheric infrared radiation, it is found that the instrument radiation is very strong, the atmospheric radiation is very weak. The two types of radiation signals are fully coupled. The background signal of the instrument radiation will greatly occupy the full-well electrons of the infrared detector and reduce system dynamic range. The instrument radiation also varies with ambient temperature. All of these lead to the accuracy of the system to measure atmospheric radiation very low. In order to improve the measurement accuracy, improve the dynamic range of the system, peel off the influnence of instrument radiation on the atmospheric radiation signals, the calibration method of the system is carefully studied. The ternary calibration model method is used to calibrate the system, and the whole telescope system is subjected to steady low-temperature refrigeration and the temperature control. Through these key measures, the stability of the system is greatly improved, and the high precision measurement of atmospheric infrared radiation is realized finally.On the basis of realizing high-precision measurement of atmospheric infrared radiation, the atmospheric infrared radiation at different zenith angles is scan measurement. Based on the radiative transfer equation solution, by fitting the radiance with the zenith angle, the average atmospheric transmittance within the in-band can be obtained. For this reason, the average atmospheric transmittance in the M' band (4.605~4.755 um) of the Ali Observatory, the Delingha Observatory and the Huairou Observatory was measured using mentioned above the measurement system. The measurement results show that the zenith average atmospheric transmittance in Ali, Delingha and Huairou are gradually reduced in the M' band, and the weighted average of the zenith average transmittance is 0.805, 0.758 and 0.650 respectively. The infrared atmospheric transmittance in three places has fluctuations, the fluctuation of Huairou is small, only 0.073, indicate that the transmittance change of Huairou is the most stable among the three places. The transmittance of Ali is not much, it is 0.081. The fluctuation of Delingha is relatively larger, the values of fluctuations reached 0.250, indicating that its transmittance is very unstable. The transmittance fluctuation has nothing to do with the strongness and weakness of transmittance, and the place with low transmittance may be relatively stable, but in contrast, the best infrared astronomical observation effect is in Ali. For comparison, the average transmittance simulated by MODTRAN software is respectively 0.846, 0.794, and 0.623, respectively. The simulated results can basically correspond to the measured results at a certain moment, indicating that the transmittance measured by the method is reliable. This transmittance measurement method does not require obtaining complex atmospheric meteorological parameters, which is relatively simple and convenient. It is convenient to make a general assessment for the infrared atmosphere transmittance of the Astronomical Observatory during the stage of astronomical site selection.This transmittance measurement method indirectly obtains the zenith average transmittance by measuring the atmospheric infrared radiance at different zenith angles. When use the system to measure the atmospheric infrared radiance, the uncertainty of the radiance measurement results will influence final fit transmittance result. Therefore, in the process of analyzing the theoretical error of the average atmospheric transmittance, the measurement error of atmospheric infrared radiation is first analyzed, including random error, the calibration error and the extrapolation error. The result shows that the measurement error of this system in the calibration region is mainly composed of the radiometric calibration error and random error, whose value is 2.4719%, 0.0790% respectively; and whose composite error is 2.4732%. For most of some best astronomy sites, the atmospheric radiant intensity is far lower than the radiant intensity at calibration, so extrapolation measuring is necessary when using this system to measure atmospheric infrared radiation. The estimation result of extrapolation error suggests that extrapolation measurement can lead to higher measurement error. Therefore, in order to improve the precision of atmospheric background radiation measurement, the standard radiation sources with lower radiant intensity are indispensable. After comprehensively considering various types of errors, the theoretical error of the atmospheric radiation measurement is 12.64%. The theoretical error of acquisition the zenith average atmospheric transmittance is less than 10% by the error transmission analysis method. Therefore, in the process of analyzing the theoretical error of the average atmospheric transmittance, the measurement error of atmospheric infrared radiation is first analyzed, including random error, the calibration error and the extrapolation error. The result shows that the measurement error of this system in the calibration region is mainly composed of the radiometric calibration error and random error, whose value is 2.4719%, 0.0790% respectively; and whose composite error is 2.4732%. For most of some best astronomy sites, the atmospheric radiant intensity is far lower than the radiant intensity at calibration, so extrapolation measuring is necessary when using this system to measure atmospheric infrared radiation. The estimation result of extrapolation error suggests that extrapolation measurement can lead to higher measurement error.Therefore, in order to improve the precision of atmospheric background radiation measurement, the standard radiation sources with lower radiant intensity are indispensable. After comprehensively considering various types of errors, the theoretical error of the atmospheric radiation measurement is 12.64%. The theoretical error of acquisition the zenith average atmospheric transmittance is less than 10% by the error transmission analysis method.
学科领域	天文学 ; 天体物理学 ; 实测天体物理学
学科门类	理学 ; 理学::天文学
页数	61
语种	中文
文献类型	学位论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/25433
专题	天文技术实验室
作者单位	中国科学院云南天文台
第一作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	陈双远. 大气红外透过率测量[D]. 北京. 中国科学院大学,2019.

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