绝对辐射计一次反射不等效的影响及实验分析

Effect and Experiment Analysis of First Specular Reflection Error on Absolute Radiometers

为了提高星载光辐射测量精度,满足在轨测量数据向世界辐射参考标准溯源的需求,运用有限元单元法对太阳辐照度绝对辐射计(SIAR)的光电不等效性进行修正。SIAR采用典型的正圆锥腔结构及加热丝直接埋入银锥腔工艺,其光电不等效性源于激光加热照射时一次反射引起的偏差。针对该偏差定量修正难度较大的特点,结合SIAR腔组件的实际结构,建立与实验测量结果最大相对误差仅为0.86%的有限元体系,并运用该体系对SIAR的光电不等效性进行定量修正。修正结果表明,光束的一次反射引起了激光加热和电加热阶段的不同功率分布,其光电不等效性因子为1.0000589,不确定度为3.4×10-6。运用该因子对测量数据进行修正,得到SIAR的太阳总辐照度实际测量结果为(1365.70±1.24)W/m2。该修正完善了绝对辐射计的修正体系。

In order to enhance the measurement accuracy of spaceborne solar irradiance and make its traceability value closer to the world radiometric reference, a finite element method is used to correct the opto- electric nonequivalence of solar irradiance absolute radiometers（SIAR）. The positive cone cavity is used in the SIAR and the heating wires are embedded into the thin walls. Thus, the opto-electric nonequivalence of SIAR is mainly derived from the drift driven by the first specular reflection. As it is difficult to measure the error in laboratory, the finite element system based on the structure of SIAR is established to quantitatively correct the nonequivalence, the relative error between the results obtained by the experiment and the finite element system is 0.86%. The results show that the power distribution of laser heating and electric heating is different due to the drift driven by the first specular reflection, the nonequivalence factor is 1.0000589, and the uncertainty is 3.4×10- 6. The radiant power measurement is modified according to this factor, and the final total solar irradiance value is（1365.70 ± 1.24） W/m2.The correction improves the revision system of SIAR.