基于超连续激光光源的细分光谱扫描定标方法研究

The finely spectrally-resolved calibration method is a key technique for the highly accurate calibration of remote sensors. The traditional monochromator illuminated by a lamp is versatile but possesses low optical throughout which limit the application in the highly accurate calibration of remote sensors. The integrating sphere illuminated by tunable laser is highly accurate but complex ,and can just span limited band coverage in China, because of the lack of infrared lasers.The supercontinuum laser source is a very promising laser source with broad spectrum, lots of researches have been conducted and great achievements have been made in China. Thereby, the supercontinuum laser and the monochromator will be adopted and studied in this proposal. First, building a finely spectrally-resolved scanning calibration equipment with excellent performances through the optimal system design and highly accurate trace to the radiometric and spectral standards; Second, conducting the research on the correction of the stray light and bandpass effects for the remote sensors through the finely spectrally-resolved scan. Third , implementing the comparison with the calibration method based on the broadband source, evaluating and correcting the systemic differences between the two calibration methods to realize the compatibility of calibration results and traceability standards between the two calibration methods. The uncertainties of the calibration method in this proposal are expected to be less than 0.1nm for the spectral calibration and less than 0.5% for the radiometric calibration. The proposal is aimed at trying to demonstrate the usability of the supercontinuum laser in calibration domain, and developing a new method for the finely spectrally-resolved method to support the highly accurate calibration of the earth-viewing remote sensors operating in the solar reflective band in China.

细分光谱扫描定标方法是遥感器高精度定标的重要手段。传统灯照明的单色仪光谱细分系统易操控但光通量低，限制了其在高精度定标中的应用；可调谐激光-积分球光谱扫描系统精度高但操作、维护复杂，在我国还受红外激光器匮乏等关键因素制约。超连续激光是一种新型的宽波段激光，应用潜力巨大，在我国具有良好的研究基础。本项目拟采用该光源与单色仪结合开展细分光谱扫描定标方法研究：（1）通过优化设计及高精度光谱、辐射标准溯源，构建高精度细分光谱定标实验平台；（2）通过细分光谱扫描，开展遥感器杂散光及带宽影响校正算法研究；（3）开展与宽波段光源定标方法比对研究，评估并校正两种定标结果的差异，实现两种定标方法溯源标准的统一及定标结果的一致。本项目所述的细分光谱扫描定标方法，预期波长定标精度优于0.1nm，辐射定标精度优于0.5%。本项目是新式光源在定标领域的应用尝试，为细分扫描定标方法探索新的技术途径，有望为我国太阳反射波段遥感器全谱段高精度定标提供支持。

基于可调谐光源的细分光谱扫描定标方法适用于溯源于低温绝对辐射计的标准探测器传递链路，广泛应用于光学遥感器高精度的光谱辐射定标。针对目前基于传统单色仪和可调谐激光器的细分光谱扫描定标方法存在的不足，本项目提出基于“超连续激光-单色仪”的细分光谱扫描定标技术并开展相关研究。.（1）项目搭建 “超连续激光器-单色仪”定标实验平台并对其进行了详细的特性表征。建立基于激光波长计的实验平台波长溯源，实现波长精度优于0.1nm。利用硅标准探测器、铟镓砷标准探测器和热释电标准探测器建立了450nm-2500nm波段的标准探测器辐射度量, 基本覆盖太阳反射波段。.（2）项目利用所搭建的实验平台，以450nm-900nm为主要研究波段开展研究。在该波段范围的实现参考辐射计绝对光谱辐亮度响应度不确定度优于0.2%（k=1）。利用Si辐亮度计和滤光片辐射计作为待定标对象，开展基于Si参考辐亮度计的系统级光谱辐亮度响应度定标研究，实现优于0.9%（k=1）的系统级传递定标不确定度，验证了实验平台的系统级定标能力。.（3）项目开展了不同定标方法的比对验证，验证了该实验平台的系统级定标精度。利用Si待定标辐亮度计开展了“部件级”和基于实验平台的系统级定标比对，比对结果相对偏差优于0.9%；利用Si辐亮度计和滤光片辐射计开展实验平台和可调谐激光器系统两种系统级定标方法的比对，Si辐亮度计光谱辐亮度响应度比对结果相对偏差优于0.6%；滤光片辐射计通道绝对光谱辐亮度响应度相对偏差优于0.5%，通道辐亮度响应度相对偏差优于0.11%。利用通道式偏振辐射计展示了实验平台在偏振遥感器辐射定标中的应用优势，对大气校正仪载荷样机开展了系统级定标并和宽波段光源定标方式进行比对，比对结果相对偏差优于2%，充分验证了实验平台的定标精度和通用性。.本项目在光谱仪、卫星载荷样机和辐射定标场观测设备的实验室定标方面进行了具体的应用探索，展现了其在光学遥感器光谱辐射定标方面新兴和广泛的应用前景。