基于光谱响应差异的HJ-1B热红外通道星上定标系数验证

Validation of HJ-1B Thermal Infrared Channels Onboard Radiometric Calibration Based on Spectral Response Differences

HJ-1B卫星热红外通道自发射以来共进行了7次星上黑体定标,然而针对星上定标系数的验证工作开展较少。通过半高宽法、矩方法和查找表法计算得到2009年9月14日星上定标系数。以具有较高定标精度的MODIS为参考源,基于MODIS第31,32通道和HJ-1B热红外通道的光谱响应特性,改进对应热红外通道的光谱匹配算法,建立两传感器表观辐亮度的匹配关系,进而通过Planck公式计算出HJ-1B热红外通道的等效水表亮温,通过与HJ-1B热红外通道基于星上定标系数得到的反演水表亮温进行比较,实现对星上定标系数的验证。以光谱响应差异计算的等效亮温值为285.97K,半高宽法、矩方法和查找表法星上定标系数反演亮温值分别为288.77,274.52和285.97K。结果显示,半高宽法、矩方法和查找表法星上定标系数反演亮温与光谱响应差异计算的等效亮温偏差分别为2.8,-11.46和0.02K。结果表明,HJ-1B热红外通道星上定标方法中以查找表法星上定标系数计算结果精度较高。同时证明了基于光谱响应差异的HJ-1B热红外通道星上定标系数验证方法有效可行。

Since HJ-1B was launched,7 sets of blackbody data have been used to calculate onboard calibration coefficients,but the research work on the validation of coefficients is rare.According to the onboard calibration principle,calibration coefficients of HJ-1B thermal infrared channel on Sep 14th,2009 were calculated with the half-width,moments and look-up table methods. MODIS was selected for the reference sensor,and algorithms of spectral match were improved between the HJ-1B thermal infra-red channel and MODIS 31,32 channels based on the spectral response divergence.The relationship of top of atmosphere （TOA）radiance between the remote sensors was calculated,based on which the surface leaving brightness temperature was cal-culated by Planck function to validate the brightness temperature calculated through the onboard calibration coefficients.The equivalent brightness temperature calculated by spectral response divergence method is 285. 97 K,and the inversion brightness temperature calculated by half-width,moments and look-up table methods is 288. 77,274. 52 and 285. 97 K respectively.The difference between the inversion brightness temperature and the equivalent brightness temperature is 2. 8,-11. 46 and 0. 02 K, respectively,which demonstrate that onboard calibration coefficients calculated by the look-up table method has better precision and feasibility.