基于多种亮度稳定目标的FY-3C/中分辨率光谱成像仪的反射太阳波段辐射定标

分析研究了风云-3C中分辨率光谱成像仪(FY-3C/MERSI)发射一年以来反射太阳波段的辐射定标精度,利用位于全球范围内的沙漠、盐湖等12种亮度稳定目标,结合中分辨率成像光谱仪(MODIS)的地表和大气参数产品和大气辐射传输模型,计算出了卫星过境时刻入瞳处的波段反射率,并将其作为在轨绝对辐射定标精度检验的参考真值,对2014年1月~10月期间,FY-3C/MERSI反射太阳波段的辐射定标精度进行了验证分析。结果表明,FY-3C/MERSI大部分波段在高低端的定标精度大小不一致。有些波段明显呈现高端定标偏差大,低端定标偏差小的特点;有些波段呈现高、低端定标偏差大,中间低的特点。在仪器发射一年以来,波段1~4,9~11,15~16和波段19仍能保持5%的定标精度。各波段定标精度的时间变化表明:在整个研究时期内,除蓝光波段和水汽吸收波段,其他波段的定标精度变化幅度基本在5%以内。实验结果显示:使用沙漠及盐湖等多种亮度稳定目标,有效地掌握了更宽动态范围内FY-3C/MERSI的辐射定标精度情况。

FY-3C/MERSI caliration for solar band using multi-reflectance stable targets

The calibration accuracy of solar bands for Fengyun-3C/Moderate Resolution spectral Imager(FY-3C/MERSI) from January 2014 to October 2014 is assessed based on multi-reflectance stable targets, such as deserts and salt lakes with different reflectances in a globe. In combination of ground surface and atmospheric parameters of Moderate Resolution Imaging Spectroradiometer(MODIS) products and the atmospheric radiation transfer model, the band reflectances of the satellite when it transits into the pupil are calculated and then they are taken as the reference true values for validation of the absolute radiation calibration accuracy. The validation experiments on radiation calibration accuracy of the FY-3C/MERSI for reflective solar bands are performed for the dates mentioned above. The results show that the calibration accuracy of most solar bands of FY-3C/MERSI is different for the targets with different reflectances. For some bands, the calibration accuracy is lower for larger reflectance targets, and higher for lower reflectance targets. For other bands, the calibration accuracy is lower for larger and lower reflectance targets, and higher for targets with moderate reflectances. Bands 1~4, 9~11, 15~16 and band 19 of FY-3C/MERSI can maintain a calibration accuracy of 5% during one year after its launching. The time series of the calibration accuracy of each band show that the variation of the calibration accuracy for the whole study period is within 5% except for the blue band and the water vapor absorption bands,. It concludes that it is effectively to acquire a good knowledge of the radiometric calibration accuracy over a wider dynamic range for FY-3C/MERSI by using the deserts and salt Lakes simultaneously.