利用定标光谱仪(SCS)实际光学系统参数,分析了经太阳衰减屏(SAC)衰减后的太阳漫反射板(SD)的出射辐亮度非均匀性来源。基于星上定标时刻漫反射板光谱辐亮度物理模型,结合实验室部分实测参数计算得到整年星上定标时段的漫反射板出射辐亮度角度变化规律,并与以实验室小发散角太阳模拟器作为照明光源测得的SCS漫反射板出射辐亮度随照明角度变化的规律进行了比较,验证了星上漫反射板定标时刻光谱辐亮度物理模型的正确性,且光通过太阳衰减屏照明漫反射板得到的出射辐亮度在SCS焦平面的能量非均匀性可优于0.47%/(°),满足SCS相对辐射定标对辐射源工作区域在其焦平面均匀性优于99.5%的要求。最后,根据实际应用状态,分析得到太阳衰减屏+漫反射板方式形成的星上光谱辐亮度标准面源量值不确定度可优于2.13%。

Based on the actual optical system parameters of the calibration spectrometer (SCS), the source of the radiance non-uniformity of the solar diffuser (SD) attenuated by the solar attenuation screen (SAC) is analyzed. Based on the physical model of the SD spectral radiance in orbit while calibration, combined with part of the parameters measured in the laboratory, the variation law of the SD’s radiance versus the angle of incidence (AOI) during the calibration measuring in a year is obtained. And comparing with the variation law of the SD radiance versus AOI set on SCS mearsured with a small divergence solar simulator as the source for illuminating in the laboratory, the correctness of the physical model of spectral radiance at the calibration time of the SD in orbit is verified. The emission radiance obtained by the illuminating SD can achieve energy non-uniformity in the SCS focal plane of better than 0.47%/(°), which satisfies the requirement that the SCS relative radiation calibration has a focal plane uniformity better than 99.5% at the working area of the radiation source. Finally, according to the actual application state, the uncertainty of the on-board spectral radiance standard surface source value formed by the SAC+SD method can be better than 2.13%.