基于海洋耀斑的多角度偏振成像仪在轨偏振定标技术

Onboard Polarization Calibration Technique of Multi-Angle Polarization Imager Based on Sun Glint from Ocean

提出了基于海洋耀斑的在轨偏振定标方法,首先建立海洋粗糙面模型,分析洋面耀斑偏振辐射特性;其次,考虑到大气辐射传输特性,使用6SV辐射传输模型计算大气层顶(TOA)的耀斑偏振特性;然后,进一步修正气溶胶偏振的影响,提出TOA偏振度修正公式,采用t检验方法验证所提公式中新加二次项的显著性;最后,建立关于太阳天顶角的修正系数查找表,得到模拟偏振度。对POLDER 3解析偏振度进行验证,其相对误差低于2%。利用所提方法对多角度偏振成像仪(MAPI)进行偏振定标,偏振定标精度约为2%,可满足仪器偏振精度要求。根据不确定度分析可知,所提方法的偏振度总不确定度为1.43%。

This study reports a method for the calibration of onboard polarization based on sun glint.First,a rough-surface ocean model was used to analyze the polarization radiation characteristics of the sun glint from the ocean.For radiation transmitted through the atmosphere,the 6SV radiation transmission model was used to calculate the polarization characteristics at the top of the atmosphere(TOA).Further,to correct the effects of aerosols,a correction formula for TOA polarization was proposed;the t test was used to verify the significance of the new quadratic term of the correction formula.Finally,the correction coefficient lookup table for solar zenith angles was established to calculate the simulated degree of polarization.Using polarization data obtained from the radiance observed by POLDER 3,the relative error was verified to be less than 2%.Compared with the degree of polarization observed by the multi-angle polarization imager(MAPI),the polarization calibration accuracy was approximately 2%,which meets the requirements of the instrument polarization precision.The uncertainty showed that the synthetic uncertainty of polarization obtained using this method was 1.43%.