风云三号B星(FY-3B)上地球辐射探测仪的绝对辐射定标及其与Aqua卫星上云和地球辐射能量系统(CERES)数据之间的对比

Absolute Radiometric Calibration of Earth Radiation Measurement on FY-3B and Its Comparison with CERES/ Aqua Data

风云三号B星（FY-3B）携带的地球辐射探测仪（ERM）通过窄视场（NFOV）扫描和宽视场（WFOV）非扫描方式来观测地球大气。每种视场包括两个宽带通道，即光谱范围在0.2～50μm的全波段通道和在0.2～4.3μm之间的短波通道。将ERM观测去滤波的长波辐射、短波辐射与美国地球观测系统（EOS）Aqua卫星携带的云和地球辐射能量系统（CERES）飞行模式（FM）3中观测数据对比来检验ERM的定标。ERM的长波辐射和短波辐射与CERES数据具有较好的相关性，二者之间存在一定系统偏差。利用CERES数据对ERM数据做光谱订正。经过订正后，ERM长波辐射偏差会从-3.00W/（sr·m2）减小到-0.60W/（sr·m2），短波辐射的偏差从6.00W/（sr·m2）减小到4.00W/（sr·m2）。根据ERM在轨内定标数据分析了ERM长波及短波通道辐射响应的稳定性，结果显示全波通道长波部分较为稳定并且变化率小于1.5%，与之相比，短波通道变化较大，变化率超过3%。这些变化可能是由于探测器的退化而引起的，NFOV短波通道在轨运行8个月后因故障失效。

The Earth Radiation Measurement(ERM) instrument onboard FengYun(FY)-3B satellite observes the Earth's atmosphere with a narrow scanning field of view(NFOV) and a wide nonscanning FOV(WFOV).For each field of view,the measurements are made from two broadband channels: a total waveband channel covering 0.2–50 μm and a shortwave(SW) band covering 0.2–4.3 μm.The validation to the ERM calibration was carried out by comparing the unfiltered longwave(LW) and SW radiances from ERM with those from Clouds and Earth's Radiation Energy System(CERES) flight model(FM) 3 onboard Earth Observing System Aqua satellite.While the ERM LWand SWradiances have a good correlation with CERES data,there is a systemic bias between the two data sets.A spectral correction is made for the ERM data using the CERES data.After the correction,the error of the ERM LW radiance is reduced from 3.00 to 0.60 W/(sr·m2).For the SW radiance,the bias is reduced from 6.00 to 4.00 W/(sr·m2).Based on the ERM in-orbit calibration data,the stability of the ERM LW radiometric response is analyzed,and it is shown that the gains are stable with a variation of less than 1.5% during its first 9months in orbit.However,the gains at the SWchannels have larger changes and exceed 3%.These drifts might be caused by the detector degradation.Also,the NFOV scanner at the SW channel is no longer working after its 8 months in orbit.