EMI-NL星载光谱仪暗电流分析处理方法  

Dark Current Analysis and Processing Method of Environment Monitoring Instrument Nadir and Limb

作　　者：林方 刘文清 王煜[3] 常振 张泉 司福祺 LIN Fang;LIU Wen-qing;WANG Yu;CHANG Zhen;ZHANG Quan;SI Fu-qi(School of Environmental Science and Optoelectronic Technology,University of Science and Technology of China,Hefei 230026,China;Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;Institutes of Physical Science and Information Technology,Anhui University,Hefei 230039,China)

机构地区：[1]中国科学技术大学环境科学与光电技术学院,安徽合肥230026 [2]中国科学院合肥物质科学研究院安徽光学精密机械研究所,安徽合肥230031 [3]安徽大学物质科学与信息技术研究院,安徽合肥230039

出　　处：《光谱学与光谱分析》2025年第3期789-797,共9页Spectroscopy and Spectral Analysis

基　　金：国家重点研发计划项目(2022YFB3904805)资助。

摘　　要：EMI-NL星载成像光谱仪应用于监测大气痕量气体的全球分布,搭载电荷耦合器件探测器CCD275,该电荷耦合器件探测器为国内首次应用,由于整体体积和功耗相较一般探测器更大,采用辐射制冷配合加热器的温控方案。星载成像光谱仪工作在太阳同步轨道,白天拍摄原始光谱图像,黑夜拍摄暗背景图像,原始光谱图像和暗背景图像需要在相同的温度和曝光时间条件下进行拍摄,数据处理过程中,用原始光谱图像减去暗背景图像,获得有效光谱图像,用于后续的气体反演。辐射制冷器在轨运行过程中,有制冷效率降低或完全失效的风险,这会导致CCD275的温度无法控制,采集相同温度的原始光谱图像和暗背景图像成为问题。为了解决温控失效后的特定温度暗背景采集问题,提出了一种通过计算暗背景代替采集暗背景的方式:通过采集两组温度已知并且曝光时间不同的暗背景图像,计算特定温度和曝光时间下的暗背景。讨论了EMI-NL光谱仪的工作原理、温控方案和暗背景采集方式,通过对探测器暗电流特性的研究,以及对探测器连续帧转移成像方式的分析,推导出了探测器不同位置像元的像元值与探测器成像温度和曝光时间的关系公式,并基于该公式提出了暗背景的计算方法。为验证该方法,搭建了包括真空系统、制冷系统和成像电路在内的实验平台,平台能够控制探测器工作在指定的温度和曝光时间,并获得该条件下的暗背景。测试结果表明,对单点来说,计算图像与实测图像的相关性达到99.96%,像元值偏差范围为0.06%~6.9%。对278 K温度下的图像来说,计算暗背景与实测暗背景均值相差0.23%,方差相差-3.20%,相关系数为99.94%,像元值偏差范围为-0.70%~2.37%,暗背景特征点匹配率达到97.9%。在温控失效的情况下,计算暗背景能够代替实测暗背景用于光谱图像的处理。EMI-NL satellite-borne imaging spectrometer utilizing charge-coupled device CCD275 is applied to monitor the global trace gases of the atmosphere.This spectrometer is the first application of CCD275 in China.Since its overall volume and power consumption are more significant than usual CCD detectors,CCD275 uses the thermal design of radiant coolers with heaters.The satellite-borne imaging spectrometer works in a sun-synchronous orbit.It captures original spectrum images during the day and dark background images at night.The original spectrum and dark background images must be captured under the same temperature and exposure time conditions.During the data processing,the dark background images are subtracted from the original spectrum images to obtain valid spectral images for subsequent retrieval of the trace gases.During the on-orbit operation of the radiant cooler,there is a risk of cooling efficiency decrease or complete failure.The risk leads to the temperature control failure of the CCD275,and collecting original spectrum images and dark background images at the same temperature becomes a problem.This paper proposes a method to calculate the dark background images instead of acquiring one to solve the problem of dark background collection at a specific temperature after thermal control failure.This method could calculate the dark background images at any specific temperature and exposure time by collecting two sets of dark background images with known temperatures and different exposure times.This paper discusses the working principle,the thermal design,and the dark background collection method of the satellite-borne spectrometer.The relationship formula,which the method mentioned above is based on,between pixel value,temperature,and exposure time is deduced from the analysis of dark current characteristics and the continuous frame transfer imaging mode.To verify this method,this paper built an experimental platform that included a vacuum system,cooling system,and imaging circuit.The platform can set the det

关 键 词：星载成像光谱仪 电荷耦合器件 暗背景 辐射制冷 

分 类 号：TH744[机械工程—光学工程] TN386.5[机械工程—仪器科学与技术]