Abstract
Suomi-NPP VIIRS contains a visible imaging band designed to produce imagery both during daytime and nighttime called the Day-Night Band (DNB). The DNB is composed of a three gain stage backside illuminated Charged Coupled Device (CCD) with 4 light sensitive elements that aggregate the individual CCD pixels in 32 different aggregation modes across scan yielding imagery with a roughly constant Horizontal Sampling Interval (HSI). The highest gain stage is over 100,000 times more sensitive than the lowest gain stage; the combination of the three gain stages allows for imagery to be obtained with radiances from 10-10 W/cm2/str to 10-2 W/cm2/str.
The current DNB on-orbit calibration relies on a monthly special operation to determine the dark offset and transfer the lowest gain stage calibration to other gain stages. This calibration approach results in discrete calibration and the loss of some science data. In this study, we will present a new calibration method based solely on VIIRS calibration data. The calibrator data collected on the night side of the orbit are used to determine the dark offset and the data collected over the terminators and daytime orbit are used to compute the cross-stage gain ratios. This calibration method should be more accurate because the calibrator data is not affected by night glow contamination and is less affected by straylight. The calibration is also continuous as calibrator data are recorded for each scan. Because no special operation is required, this method can be operationally implemented to ensure continuous DNB calibration.
A New Method for Suomi-NPP VIIRS Day Night Band (DNB) On-Orbit Radiometric Calibration
Suomi-NPP VIIRS contains a visible imaging band designed to produce imagery both during daytime and nighttime called the Day-Night Band (DNB). The DNB is composed of a three gain stage backside illuminated Charged Coupled Device (CCD) with 4 light sensitive elements that aggregate the individual CCD pixels in 32 different aggregation modes across scan yielding imagery with a roughly constant Horizontal Sampling Interval (HSI). The highest gain stage is over 100,000 times more sensitive than the lowest gain stage; the combination of the three gain stages allows for imagery to be obtained with radiances from 10-10 W/cm2/str to 10-2 W/cm2/str.
The current DNB on-orbit calibration relies on a monthly special operation to determine the dark offset and transfer the lowest gain stage calibration to other gain stages. This calibration approach results in discrete calibration and the loss of some science data. In this study, we will present a new calibration method based solely on VIIRS calibration data. The calibrator data collected on the night side of the orbit are used to determine the dark offset and the data collected over the terminators and daytime orbit are used to compute the cross-stage gain ratios. This calibration method should be more accurate because the calibrator data is not affected by night glow contamination and is less affected by straylight. The calibration is also continuous as calibrator data are recorded for each scan. Because no special operation is required, this method can be operationally implemented to ensure continuous DNB calibration.