Post-launch calibration of the visible channel of the High Resolution Infrared Radiation Sounder (HIRS) on the NOAA-14 spacecraft

The post-launch degradation of the visible channel (approximate to0.67-0.71 mum) of the High Resolution Infrared Radiation Sounder (HIRS) flown on the NOAA-14 spacecraft has been determined, using a south-eastern Libyan desert site (21-23 degrees N, 28-29 degrees E) as a radiometrically stable calibration target. The annual degradation rate is observed to be 0.71 (+/-0.25)%. The relative degradation thus determined has been rendered absolute using the visible channel (channel 1; approximate to0.58-0.68 mum) of the Advanced Very High Resolution Radiometer (AVHRR) on the same spacecraft as a calibration reference.