Multichannel IR Sensor Calibration Validation Using Planck’s Law for Next Generation Environmental Geostationary Systems

Multichannel radiometric sensors such as the Advanced Baseline Imager (ABI), which will be onboard the Geostationary Operational Environmental Satellite R-Series, and the Advanced Himawari Imager (AHI), which is currently onboard Himawari 8, provide the possibility to use Planck’s law to validate the absolute calibration of each channel pre-launch as well as on orbit especially in the IR. A technique is developed to use the Planck’s law and evaluate the radiometric calibration of each of the 10 thermal infrared channels by studying their radiometric response in tandem to known brightness temperature scenes. The technique is applied to proxy pre-launch IR calibration data of ABI obtained in a cold chamber by using a cryogenic blackbody and found to reveal differences in channel to channel calibration not noticed otherwise. Such differences allow us to evaluate the uncertainty associated with radiometric calibration and channel by channel spectral response functions. Since both ABI and AHI are designed with 10 IR channels and an onboard blackbody to provide calibration, the technique can be applied in real-time on-orbit to monitor any changes. This paper presents the application of the technique to proxy ABI prelaunch data and extends to the preliminary data available from AHI on orbit.