基于光电不等效性修正的低温辐射计辐射定标基准的研究

The changes of earth's climate are closely related to the changes of solar irradiance, any tiny changes in solar irradiance will further affect the stability of the earth's ecosystem. Absolute Radiometer is the main monitoring instrument for solar irradiance measurement. However, at present, it has some problems need to be improved, for example, low measurement accuracy, and high inconsistencies between different radiometers, which lead to poor traceability. Thus the calibration accuracy can only reach to 1% scale but not meet the requirements of the climate monitoring and study of environmental change. In order to achieve high-precision observations of solar irradiance, this project establish a solar absolute radiation reference for Cryogenic Solar Absolute Radiometer based on opto-electric nonequivalence correction. The opto-electric nonequivalence correction system is based on the experimental platform for high absorption measurement and comparison of vacuum-air responsibility. The quantitative characterization is carried out by the opto-electric nonequivalence correctional model, and verified by ground test and on-orbit simulation, which significantly improve the accuracy of solar irradiance measurement. The transfer chain is based on Cryogenic Solar Absolute Radiometer and taking Multispectral Sphere Transfer Radiometer as the core, which more convenient for the power benchmark converse to the radiance standard and shorter the calibration transfer process. This project has promoted our country's space solar spectrum radiation measurement development and improved the space absolute calibration technology.

太阳辐照度的变化与地球气候的变化息息相关，它的任何微小变动都会进一步影响地球生态系统的稳定性。目前对太阳辐照度进行监测的辐射计测量精度低，不同仪器间的不一致性高，导致当前观测数据溯源性差，在轨定标精度只能达到1%量级，不能满足气候监测和环境变化研究的精度要求。为实现太阳辐照度的高精度观测，本项目提出建立基于光电不等效性修正的低温辐射计辐射定标基准，以实现在轨辐射测量的绝对定标。该光电不等效性修正体系以吸收腔的高吸收率测量实验和真空-空气响应度对比实验为基础，结合光电不等效性修正模型进行定量表征，采用地面测试和在轨模拟的方法进行验证，能够实现辐射计的高精度测量。此外，该基准的传递以低温绝对辐射计为标准源，以积分球传递辐射计为核心，将显著缩短基准传递过程，实现功率基准向亮度标准的转换。本项目推动了我国空间太阳光谱辐射测量事业以及空间绝对定标技术的发展。

太阳辐照度的变化与地球气候的变化息息相关，它的任何微小变动都会进一步影响地球生态系统的稳定性。目前对太阳辐照度进行监测的辐射计测量精度低，不同仪器间的不一致性高，导致当前观测数据溯源性差，定标精度只能达到1%量级，不能满足气候监测等领域对遥感数据精度达到0.1%量级的要求。为实现太阳辐照度的高精度观测，本项目提出在原有常温绝对辐射计的研究基础上，搭建地面基准的低温绝对辐射计实验平台，并重点探究辐射测量过程中光电不等效性的产生机理，解决其中的关键问题。经过三年的探索和研究，本项目:(1)建立了基于低温绝对辐射计实际结构的有限元模型，与实际温度响应的最大灵敏度差异仅为1×10-3K/mW，最大相对误差为0.08%；(2)利用傅立叶变换和分离变量法，建立了适用于绝对辐射计的一维热传导温度响应表达形式；(3)采用PID控制方法，利用LABVIEW和MATLAB软件，实现了低温辐射计热沉温度的精准控制，不确定度为0.00019K；(4)设计了一种新的热结构设计对低温辐射计光电不等效性进行优化，进一步了提高热沉的稳定性；(5)建立了低温绝对辐射计的光电不等效性修正体系，该修正缩小了低温绝对辐射计测量值与世界辐射中心辐射标准的误差，提高了低温绝对辐射计的测量精度，解决了辐射测量数据SI可溯源性差的问题。