Abstract
On-board radiometric calibration of Day Night Band (DNB) on the National Oceanic and Atmospheric Administration (NOAA) 20 Visible Infrared Imaging Radiometer Suite (VIIRS) is based on the Solar Diffuser (SD) observations in the Low Gain Stage (LGS). DNB is a unique panchromatic band which has a broad spectral response covering a wavelength range roughly from 500 nm to 900 nm with over 7 orders of magnitude in radiometric dynamic range. To cover such a wide dynamic range, DNB has High Gain Stage (HGS), Middle Gain Stage (MGS), and LGS in the sensor design. The radiometric calibration of DNB MGS and HGS depends on the SD-based LGS gain estimation and then transferred to the MGS and HGS through gain ratios.
The on-orbit NOAA-20 DNB LGS gains have been derived daily from the on-board SD observations since its launch on November 18, 2017. Using the scheduled lunar observations of VIIRS as the independent radiometric calibration source, the lifetime SD-based DNB LGS gains can be independently validated. The NOAA-20 DNB lunar F-factors (or calibration coefficient) are derived through analyzing the lunar irradiance ratio between VIIRS lunar observations and the lunar irradiance model. i.e. the Global Space-based Inter-Calibration System (GSICS) Implementation of RObotic Lunar Observatory (ROLO) (GIRO). The primary on-orbit SD-based NOAA-20 DNB radiometric calibration is validated by the lunar F-factors. It is found that the difference between SD-based calibration coefficient and lunar-F factor for NOAA-20 DNB LGS is within two percent based on the analysis of 4 years of NOAA-20 VIIRS DNB measurements.
NOAA-20 VIIRS Day Night Band (DNB) Radiometric Calibration using Solar Diffuser and Lunar Observations
On-board radiometric calibration of Day Night Band (DNB) on the National Oceanic and Atmospheric Administration (NOAA) 20 Visible Infrared Imaging Radiometer Suite (VIIRS) is based on the Solar Diffuser (SD) observations in the Low Gain Stage (LGS). DNB is a unique panchromatic band which has a broad spectral response covering a wavelength range roughly from 500 nm to 900 nm with over 7 orders of magnitude in radiometric dynamic range. To cover such a wide dynamic range, DNB has High Gain Stage (HGS), Middle Gain Stage (MGS), and LGS in the sensor design. The radiometric calibration of DNB MGS and HGS depends on the SD-based LGS gain estimation and then transferred to the MGS and HGS through gain ratios.
The on-orbit NOAA-20 DNB LGS gains have been derived daily from the on-board SD observations since its launch on November 18, 2017. Using the scheduled lunar observations of VIIRS as the independent radiometric calibration source, the lifetime SD-based DNB LGS gains can be independently validated. The NOAA-20 DNB lunar F-factors (or calibration coefficient) are derived through analyzing the lunar irradiance ratio between VIIRS lunar observations and the lunar irradiance model. i.e. the Global Space-based Inter-Calibration System (GSICS) Implementation of RObotic Lunar Observatory (ROLO) (GIRO). The primary on-orbit SD-based NOAA-20 DNB radiometric calibration is validated by the lunar F-factors. It is found that the difference between SD-based calibration coefficient and lunar-F factor for NOAA-20 DNB LGS is within two percent based on the analysis of 4 years of NOAA-20 VIIRS DNB measurements.