卫星载荷在轨场地定标是校正星载遥感器响应度变化的基本手段，地表反射率是场地定标的关键输入参数之一，针对目前卫星数据定量化应用需求的提升，迫切需要解决基于参考板的地表反射率间接测量对场地定标不确定度的影响。为提升地表反射率的长期观测精度，项目开展校正场反射率直接测量方法和自校准技术研究。（1）研究单光学系统测量天空总照度和地表辐亮度的技术方法，设计以余弦校正器和观测镜头为核心的前置光学系统，解决双光路大动态范围光通量匹配难题，实现地表反射率的直接法观测。（2）开展基于太阳直射的反射率观测自校准技术研究，解决系统比值透过率定标问题，实现地表反射率长期观测精度的一致性。（3）实验室系统级定标保障地表反射率测量不确定度优于1.0%，校正场在轨定标比对试验评估直接法测量精度的提升效果。项目的开展将为卫星遥感器的高精度定标和数据一致性奠定研究基础，为我国正在构建的空间观测体系提供在轨场地定标技术支撑。

On-orbit field calibration is a basic method to correct the responsivity change of the satellite sensors, and surface reflectance is one of the key input parameters of field calibration. To meet the increasing requirements of quantitative applications of the satellite data at present, the impact of the spectral reflectance indirect measurement which is based on reference panel on the uncertainty of field calibration need to be resolved and removed urgently. In order to upgrade the long-term precision of the surface reflectance, the direct-method measurement and self-calibration technology of the spectral reflectance is suggested in this proposal. First, realizing the direct measurement of surface reflectance by building a special optical system based on the cosine corrector and observation lens to measure the total sky irradiance and surface radiance, where the problem of high-dynamic-range throughput in these two optical paths should be resolved. Second, conducting the research on self-calibration technology of surface reflectance measurement to achieve the high accuracy reflectance observation and guarantee the long-term consistency, with the solar direct irradiance result which is measured by the same observation lens as the surface radiance, the problem of accurate ratio-transmittance calibration in the system should be solved in this process. Third, Guaranteeing the uncertainty of the new measurement method to be less than 1% through the system-level calibration in the laboratory, and evaluating the accuracy improvement result of the surface reflectance measurement by this new method through the on-orbit field calibration experiments.The implement of the project is expected to build the foundation for the high precision calibration and guarantee the long-term data consistency of the satellite remote sensors. The research achievements can prospectively provide technical support for the field calibration of space observation systems in China.