可见光—短波红外光谱辐射计现场量值传递方法

Field dissemination of the value of the quantity method of thespectroradiometer in visible-to-shortwave infrared

外场辐射测量是光学遥感研究的重要信息来源,为了保证外场测量数据的准确性,外场设备必须进行量值溯源。本文旨在开展外场光谱测量设备的现场量值传递方法研究,将外场测量设备的辐射测量水平溯源至统一基准,以此来保证外场测量时设备获取数据精准性以及数据质量一致性。通过分析实验室和外场光源差异、测量环境差异等因素对辐射量值准确性的影响,建立了杂散光修正模型和环境温度修正模型,构建了完整的从实验室到外场的量值传递链路,采用对称放置和互换测量的方法将光谱辐射量值从实验室国家基准有效传递至外场观测设备,实现了实验室到外场380—2400 nm波长的光谱辐射量值传递。进一步地,依据不确定度传播律,分析了可见光短波红外光谱辐射计现场量值传递的不确定度,最终实现量传光谱仪测量不确定度1.7%—2.3%(k=1)和外场观测设备定标不确定度1.9%—2.5%(k=1)。本文对于量传光谱仪及现场量值传递的不确定度分析,有助于今后不同外场测量设备间的交叉验证,保证多场地基验证试验的测量一致性。

Field spectroradiometers need to be traced back to a unified benchmark,namely,the international system(SI)of units,to ensure the accuracy and consistency of different field spectroradiometers.Considering that reports focusing on the accuracy of field radiometric calibration of spectroradiometers are lacking,this study investigates the field dissemination of the value of the quantity method.The field dissemination of the value of the quantity method can be divided into two parts:calibration of a transfer spectroradiometer and field radiometric calibration.The influencing factors must be considered when a transfer spectroradiometer is used to calibrate the field spectroradiometer because of the differences between the laboratory and the actual site,such as relative spectral,radiation level,and temperature and humidity differences.Mathematical models are established to quantify the influence of various parameters on the spectral measurement accuracy,and a stray light correction model is built using the laser and filter method to correct the stray light caused by the relative spectral difference.The integrating sphere light source addition method is used to evaluate the nonlinearity at different radiation levels.In addition,whether spectral responsivity and detector temperature have a one-to-one correspondence is analyzed,and a temperature correction model is built according to the variation trend of spectral responsivity.After measuring and correcting the influence of the difference between the laboratory and actual site,the transfer spectroradiometer is utilized to transfer the radiometric quantity to the field spectroradiometer by using the symmetrical placement and exchange measurement method.Uncertainty evaluation methods,such as the model of the relationship between wavelength and spectral radiance,the stray light correction model,and the temperature correction model,are provided for the transfer spectroradiometer.Then,the radiometric quantity is transferred from the laboratory measurement standard to the transfer spectroradiometer and then to the field instruments.By analyzing the uncertainty components in the whole process,a laboratory-field dissemination method of the value of the quantity chain is established,and the field spectroradiometer is traced to the SI unit uninterruptedly.In accordance with the uncertainty propagation law,the uncertainties of the transfer spectroradiometer and field spectroradiometer are obtained.Experimental results show that the uncertainty of the transfer spectroradiometer is 1.7%—2.3%(k=1)from 380 nm to 2400 nm,and the uncertainty of the field spectroradiometer is 1.9%—2.5%(k=1)from 380 nm to 2400 nm.The paper systematically introduces the method of field dissemination of the value of the quantity method.During the field calibration process,the uncertainty and characteristics of the standard transfer spectroradiometer are investigated.By analyzing the field calibration uncertainty in the whole process,the field spectroradiometer can be traced back to the international equivalent primary standard in the laboratory.The method is helpful for the cross verification of different types of field instruments at different sites and ensures the consistency of multiple field verification tests.It can also be used to calibrate satellite optical loads with high accuracy in the future.