“高分五号”全谱段相机可展开定标漫反射板设计

为了对“高分五号”卫星全谱段光谱成像仪的太阳反射谱段辐射性进行长期监测与校正，并针对其谱段范围宽、精度要求高、口径大、使用寿命长等特点与要求，优化设计了可展开的漫反射板进行全光路全视场的辐射定标。定标漫反射板安装在相机光学系统的前端侧面，不影响相机正常成像，在定标时通过驱动机构展开漫反射板到相机前端，根据“高分五号”卫星轨道特点、定标能量要求及相机安装矩阵等设计定标漫反射板展开角度为39°。研制了430mm×430mm大尺寸聚四氟乙烯漫反射板组件以保证在展开时满足全光路全视场的定标，漫反射板在420～2400nm光谱范围内半球反射率高于95%，在相机观测方向BRDF变化优于25%。同时，设计了漫反射板稳定性监视辐射计用于监测漫反射板在轨性能衰减，监测精度15%。在轨定标精度分析为476%，满足指标要求。

Design of expandable diffuser board on GF 5 VIMI

For the long term monitoring and correcting of the radiometric performance of the imager, the expandable diffuser used for calibration in full FOV and full optical path method was designed, considering the characteristics and requirements of its wide spectrum range, high accuracy requirements, large aperture and long service life.The solar diffuser is installed on the front side of the optical system and does not affect the normal imaging of VIMI.When VIMI needs calibration，the diffuser is expanded to the front of the optical system via the driving mechanism. According to the characteristics of the GF 5 satellite orbit, the requirement of the calibration energy and the installation matrix of the imager relative to the satellite, the expansion angle of the diffuser is 39°. The 430mm×430mm large size PTEE diffuser is manufactured to ensure full FOV and full optical path calibration. The diffuser’s directional hemispherical reflectance is higher than 95% when the spectrum ranges from 420nm to 2400nm， and variation of BRDF in the direction of imager observation is better than 25%.The diffuser stability monitoring radiometer is designed to monitor the on orbit attenuation performance of the diffuser, and the monitoring accuracy is 15%. The accuracy of on orbit calibration is 476%, which meets the requirement of index.