FY-2B与NOAA卫星红外通道的相对定标

FY-2是自旋扫描静止气象卫星,其红外通道的在轨定标是将黑体从后光路插入目标光路中进行的,此种定标不是全光路定标,存在较大的误差。为了获得较好的红外通道在轨定标系数,用定标精度较高的NOAA(16,17)卫星通道4观测数据与FY-2B红外通道观测数据进行了相对定标试验。相对定标的工作主要是两种卫星观测仪器响应函数之间的光谱匹配和观测图像之间的几何匹配。拟合匹配后两种卫星的观测数据,利用NOAA卫星较高精度的定标系数可得到改进的FY-2B定标系数。FY-2B相对定标系数的精度比原定标系数有较大的提高。

INTER CALIBRATION OF FY-2B IR CHANNEL WITH NOAA SATELLITES

FY-2 is a spin-scanning geostationary meteorological satellite.The calibration of IR channel in-orbit was to insert a blackbody into objective optical path from back-end optical path.There was a big error for such calibration,but that wasn't a total optic-path calibration.For the infrared channels,the pre-launch calibration was conducted in a vacuum container used to simulate the space environment.The instrument was calibrated with reference to the black body.The radiant cooler was keeping at two temperatures states,i.e.95 K,100 K in the laboratory.The objective blackbody varied with a series of the temperatures.Then the infrared sensors were measured in variety combined temperatures conditions of the primary mirror and second mirror.The sensors output voltages with response were also measured.But,the characteristic response of sensors was varying by time after the satellite launched. The pre-calibration was no longer useful.Thus the calibration post-launch was very importance.There were a variety of calibration methods post-launch about the black-body calibration,the calibration of the radiometric calibrated sites,the calibration of radiant numeric data and the inter-calibration with different satellites.The 27~(th) CGMS meeting in 1999 stressed the importance of inter-calibration.In CMA/NSMC,the inter-calibration study is carried out and is operation-oriented.The inter-calibration uses NOAA satellite data to calibrate FY-2 geostationary satellite.The data were used for calibrating FY-2 long wave IR channel.The inter-calibration examination was processed by the GAC data of AVHRR channel 4 from NOAA-16,17 that were high precision calibration.The inter-calibration jobs were mainly the spectral matching between two response functions of satellites measured sensors and the geometry matching between two images observed.The calibration coefficient of FY-2B was ameliorated by the better calibration coefficient of NOAA satellites after matching two satellites data were calculated.The inter-calibration precision of FY-2B IR channel was highly enhanced.