摘要
碳卫星超光谱探测仪聚焦于陆地生态系统植被碳汇和森林蓄积量探测,利用670~780 nm谱段的光谱绘制植被荧光的时空分布规律,满足全球碳汇定量监测、森林植被生产力评估的需求。如何有效地标定超光谱探测仪的光谱参数,建立探测仪和被测光谱信息的对应关系是定量化反演的基础。通过光栅方程推导了超光谱探测仪的光谱数据误差模型,并结合光学系统的弥散斑分布函数,卷积得到了超光谱探测仪的仪器线形函数(ILS)分布规律。仿真结果表明,仪器线形函数是缓慢变化的,在一个小光谱范围内ILS可以近似认为是一致的;波长误差是一个系统误差,主要由光栅制造误差等引起,采用已知波长特征谱线标定的方法可以消除。通过真空罐模拟在轨环境,建立了包含可调谐激光器、波长计、旋转散射片、积分球和平行光管等装置的光谱定标系统,提供线宽小于0.001 nm均匀分布的单色标准光源,利用自动化数据处理系统测试探测仪响应曲线和单色标准光源的对应关系,标定超光谱探测仪的光谱参数。超光谱探测仪光谱采样率2.5像元左右,单波长光谱的有效数据点少,无法给出ILS函数的精确数据,以0.015 nm波长间隔单波长扫描的新方法将光谱采样密度提高2个数量级,高斯拟合获取光谱分辨率,数据处理结果表明超光谱探测仪光谱分辨率为0.24~0.26 nm。通过选取特征波长和三次多项式拟合的方法得到波长定标方程,给出了全部像元的光谱定标数据,选取特征波长验证拟合波长残差,结果表明定标精度优于0.005 nm。为了进一步验证光谱定标结果,开展了超光谱探测仪的地面推扫成像实验,利用中国科学院空天院怀来试验站的测试平台,获取了松树林和石子路面的光谱数据,超光谱探测仪测量的大气吸收线和HITRAN模拟的大气吸收线比对结果表明,氧吸收线中心波长偏差小于0.003 nm,证明超光谱探测仪光谱定标精度满足指标要求。
Hyperspectral monitor on CarbonSat focuses on the detection of vegetation carbon sink and forest stock in the terrestrial ecosystem by detecting the spectrum of 670~780 nm,mapping the temporal and spatial distribution vegetation fluorescence to meet the needs of global carbon sink quantitative monitoring and forest vegetation productivity assessment.How to effectively calibrate the spectral parameters of HSM,establishing the relationship between the detector and the measured spectral information is the basis of quantitative inversion is the basis of quantitative radiance inversion.This paper gave the spectral data error model of HSM by grating equation,combined with the spot distribution function of the optical system,the Instrument Line Shape(ILS)of HSM is obtained.The simulation results show that the ILS changes slowly,and the ILS is approximately the same in a small spectral range.The wavelength error is mainly caused by grating manufacturing.It can be eliminated by the spectral line calibration method.In order to realize the spectral calibration of HSM on the ground,a calibration system that includes the tunable laser,wavelength meter,and rotating engineering diffuser is established in the vacuum tank.A monochromatic light with a linewidth less than 0.001 nm is provided,and the automatic data processing program is used to test the relationship between the response curve of the detector and the monochromatic light.The spectral sampling rate of HSM is about 2.5 pixels,and the effective data points of the single wavelength spectrum are limited.For getting accurate data of ILS,the spectral sampling rate is increased by two orders of magnitude by wavelength scanning at 0.015 nm wavelength interval,and the spectral resolution is obtained by Gaussian fitting.The results show that the spectral resolution of the HSM is 0.24~0.26 nm.The wavelength calibration data of all pixels is obtained by selecting the characteristic wavelength and cubic polynomial fitting.The characteristic wavelength is selected to verify the fitting residual.The results show that the calibration accuracy is better than 0.005 nm.In order to further verify the spectral calibration results,the ground push broom imaging experiment of HSM was carried out.The spectral data of pine forest and gravel pavement were obtained at the Huailai test station of the Aerospace Academy of the Chinese Academy of Sciences.The comparison results between the atmospheric absorption line measured by HSM and the atmospheric absorption line of HITRAN show the deviation of the central wavelength of the oxygen absorption line is less than 0.003 nm.The calibration result satisfied the system requirement HSM.
作者
杜国军
张玉贵
崔博伦
江澄
欧宗耀
DU Guo-jun;ZHANG Yu-gui;CUI Bo-lun;JIANG Cheng;OU Zong-yao(Beijing Institute of Space Mechanics&Electricity,Beijing 100190,China)
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2023年第5期1556-1562,共7页
Spectroscopy and Spectral Analysis
基金
国家重点研发计划项目(2016YBF0500503)资助。
关键词
超光谱成像
定标
光谱分辨率
ILS
大气吸收
Hyperspectral imaging
Calibration
Spectral resolution
ILS
Atmosphere absorption
