基于场地高光谱BRDF模型的Suomi-NPP VIIRS长时序定标

Long Time Series Radiometric Calibration of Suomi-NPP VIIRS Based on Surface Hyperspectral BRDF Model

为提升光学卫星遥感器的定标频次,提出一种基于场地高光谱BRDF(Bidirectional Reflectance Distribution Function)模型的高频次绝对辐射定标方法,实现了Suomi-NPP(Suomi-National Polar-Orbiting Partnership Spacecraft)VIIRS(Visible Infrared Imaging Radiometer Suite)的长时序高频次绝对辐射定标。介绍了基于场地高光谱BRDF模型的绝对辐射定标原理,于2018年4月和8月利用场地高光谱BRDF手动测量系统分别对敦煌场的方向特性进行测量试验,并基于半经验核驱动反演敦煌场的地表高光谱BRDF模型参数。基于BRDF模型计算2018年全年VIIRS M1~M11波段的表观反射率,并与卫星观测表观反射率进行比对。结果表明:Suomi-NPP VIIRS遥感器2018年全年的有效定标频次为51次,其中M1~M7波段模型计算的表观反射率与卫星观测的相对偏差均小于3.23%。基于场地BRDF模型的高频次绝对辐射定标方法可有效地提高卫星载荷的定标频次,及时跟踪载荷的辐射特性变化。

In order to improve the calibration frequency of optical satellite remote sensors,a high-frequency absolute radiometric calibration method based on the surface hyperspectral bidirectional reflectance distribution function(BRDF)model is proposed,and the long time series absolute radiometric calibration of Suomi-national polar-orbiting partnership spacecraft(Suomi-NPP)visible infrared imaging radiometer suite(VIIRS)is realized.The principle of the absolute radiometric calibration method based on the surface hyperspectral BRDF model is introduced.In April 2018 and August 2018,the surface directional reflectance of the Dunhuang test site was measured by the hyperspectral BRDF manual measurement system,and the hyperspectral BRDF model parameters of the Dunhuang site were inversed based on the semi-empirical kernel-driven model.Based on the BRDF models,the apparent reflectance of VIIRS M1-M11 bands in the whole year of 2018 was calculated,and compared with the satellite-observed ones.The results show that the effective calibration number of Suomi-NPP VIIRS is 51 in 2018,the relative deviation of model-calculated apparent reflectance and satellite-observed ones of the M1-M7 bands is less than 3.23%.The proposed method can effectively improve the calibration frequency of satellite and track the change of radiometric characteristics of the load in time.