Improved calibration coefficients for NOAA-14 AVHRR visible and near-infrared channels

An analysis of the calibration coefficients used to describe sensor degradation in channels 1 and 2 of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-14 spacecraft is presented. The radiometrically stable permanent ice sheet of central Antarctica is used as a calibration target to characterize sensor performance. Published calibration coefficients and the coefficients imbedded in the NOAA Level 1b data stream for the period January 1995 to November 1998 are shown to be deficient in correcting for the degradation of the sensor with time since launch. Calibration formulae constructed from NOAA-9 reflectances are used to derive improved calibration coefficients for the AVHRR visible and near-infrared channels for NOAA-14. Channel 1 reflectances for the Greenland ice sheet derived using the new coefficients are consistent with those derived previously using NOAA-9 AVHRR. In addition, improved reference AVHRR channel 2 reflectances for Greenland are derived from NOAA-14 observations. It is recommended that the coefficients derived in this study be used to calibrate reflectances for NOAA-14 AVHRR channels 1 and 2.