Cross-validation of HJ-1B infrared channels onboard calibration coefficients using MODIS

Since HJ-1B has been launched, 7 sets of blackbody data were used to calculate onboard calibration coefficients, but the research work on the validation of coefficients is rare. MODIS 31, 32 channels were selected as the reference sensor for the validation of the HJ-1B infrared channel onboard calibration coefficients by using the methods of spectral response divergence and linear statistical relationship. Firstly, the relationship of top of atmosphere (TOA) radiance between the HJ-1B thermal infrared channel and MODIS 31, 32 channels is calculated, and based on which the surface leaving brightness temperature is calculated to validate the brightness temperature calculated through the onboard calibration coefficients. According to the onboard calibration principle, calibration coefficients of HJ-1B infrared channel on Sep 14th ,2009 are calculated with the Half-width, moments and look-up table methods. The results show that calibration coefficients calculated by the look-up table method has better precision. The difference between the brightness temperature of look-up table method and spectral response divergence and linear statistical relationship methods are within 1 K, 0.02 K and 0.81 K, respectively, which demonstrate the feasibility of both validation methods and the spectral response divergence method has high accuracy. The study may contribute to fundamental basis for the validation of in-flight calibration of optical payload.