VIRR是搭载在我国最新一代极轨气象卫星FY-3B上的可见光红外扫描辐射计, 发射后的遥感器需要进行不断的辐射定标校准以提高数据质量, 更好的满足用户需求。 为了研究FY3B/VIRR入轨后辐射响应的衰变规律, 利用2011年—2015年敦煌辐射校正场同步试验数据, 采用反射率基法计算其反射太阳波段的辐射定标系数, 除受水汽吸收影响的波段10, 其余各波段定标系数相对标准差均小于1.5%。 以Aqua/MODIS为辐射基准验证了该方法的精度, 结果表明, 正演大气顶辐射与卫星观测值的平均偏差均小于2.5%。 基于上述五年的VIRR定标结果, 结合发射前定标系数, 计算了遥感器的年际衰变率, 结果表明: 仪器衰减显示出一定的波长依赖性, 波长越短的波段衰减越大； 与发射前定标系数相比, 入轨第一年的仪器定标系数有较大程度的变化； 随着在轨运行时间变长, 仪器衰减趋势开始减缓, 在轨运行的第二和第三年衰减均大幅减小； 从第四年开始波长<0.8 μm的波段, 有衰减增大的趋势； 在轨运行两年后, 波长>0.8 μm的波段部分年份出现了响应增加的现象； 与孙凌等的FY3A/MERSI衰减变化规律相比, 衰减率和波长的相关性是一致的, 但MERSI在0.65 μm的波段3和13均出现相应增加的现象, 而VIRR在该波长处的波段1却有衰减增大的趋势； 综合历年的衰减率可以看出, 波长较短的波段7, 8和9年衰减率基本大于5%。

The Visible and Infrared Radiometer (VIRR) boarded on FY3B which is the new generation polar orbit meteorological satellite of China needs constant radiometric calibration after launch for improving the quality of data and better meeting the needs of users. In order to investigate the radiometric response degradation of FY3B/VIRR, the radiometric calibration coefficients of its reflective solar bands are calculated by the reflectance-based method, using the in-situ experiment data of Dunhuang radiometric calibration site from 2011 to 2015. The corresponding relative standard deviation of each band’s radiometric calibration coefficient is less than 1.5%, except band 10 which is influenced by water vapor absorption. By comparing with the Aqua/MODIS observation data, the average deviation of our results is less than 2.5%. Then, the annual degradation rates of VIRR are achieved based on its five-year calibration coefficients, compared with the pre-launch calibration coefficient. This paper suggests that: (1) The degradation rate depends on the wavelength of the band, the degradation rate increases with the decrease of wavelength; (2) Compared with the pre-launch calibration coefficient, the VIRR sensor shows dramatic radiometric response change after one-year orbiting operation; (3) In general, the degradation rate decreases with the extension of operating time, especially in the second and the third year; (4) After three-year orbiting operation, the degradation rate of the band with wavelength less than 0.8μm appear to increase; (5) After two-year orbiting operation, the radiometric response of the band with wavelength greater than 0.8μm increases in some period; (6) Comparing to the degradation changes of FY3A/MERSI proposed by Sun, both of the two sensors demonstrate a negative correlation between the degradation rate and the wavelength, but the radiometric responses of MERSI’s band 3 and 13 at 0.65 μm appear to increase, on the contrary, the degradation of VIRR’s band 1 at the same wavelength tends to increase; (7) The annual degradation rate of short wavelength band 7, 8 and 9 is greater than 5% in the long run.