Abstract
The S-NPP VIIRS has successfully operated on-orbit since its launch in October, 2011. It has 22 spectral bands: 14 reflective solar bands (RSB), 7 thermal emissive bands (TEB), and 1 day night band (DNB). The VIIRS RSB calibration is performed each orbit by the on-board solar diffuse (SD). The SD on-orbit degradation is currently tracked on a daily basis by an on-board solar diffuser stability monitor (SDSM). In addition, near-monthly lunar observations have been scheduled and implemented to independently track the RSB calibration stability. Early on-orbit observations revealed that the VIIRS rotating telescope assembly (RTA) mirrors had experienced strong wavelength dependent degradation, especially in the NIR and SWIR spectral region. Because of this, the sensor’s relative spectral response (RSR) needs to be revised and updated. It is expected that the modulated RSR due to wavelength dependent mirror degradation will have different impact on the SD and lunar calibration. This paper identifies some of the key factors that need to be considered in VIIRS SD and lunar calibration algorithms. It discusses their impact on RSB calibration and mitigation strategies developed to maintain sensor calibration quality and to generate consistent sensor data records (SDR).
Performance Assessment of S-NPP VIIRS Solar Diffuser and Lunar Calibration
The S-NPP VIIRS has successfully operated on-orbit since its launch in October, 2011. It has 22 spectral bands: 14 reflective solar bands (RSB), 7 thermal emissive bands (TEB), and 1 day night band (DNB). The VIIRS RSB calibration is performed each orbit by the on-board solar diffuse (SD). The SD on-orbit degradation is currently tracked on a daily basis by an on-board solar diffuser stability monitor (SDSM). In addition, near-monthly lunar observations have been scheduled and implemented to independently track the RSB calibration stability. Early on-orbit observations revealed that the VIIRS rotating telescope assembly (RTA) mirrors had experienced strong wavelength dependent degradation, especially in the NIR and SWIR spectral region. Because of this, the sensor’s relative spectral response (RSR) needs to be revised and updated. It is expected that the modulated RSR due to wavelength dependent mirror degradation will have different impact on the SD and lunar calibration. This paper identifies some of the key factors that need to be considered in VIIRS SD and lunar calibration algorithms. It discusses their impact on RSB calibration and mitigation strategies developed to maintain sensor calibration quality and to generate consistent sensor data records (SDR).