Abstract
NASA’s Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) mission consists of a high-accuracy reflected solar (RS) spectrometer that will measure the Earth-reflected solar radiation from International Space Station with an SI-traceable radiometric uncertainty of 0.3% (1-sigma). The CPF measurements will serve as an on-orbit reference for intercalibrating other spaceflight RS instruments. The CPF intercalibration team has designed a state-of-the-art approach to calibrate the shortwave channel (300-5000 nm) of the Clouds and the Earth’s Radiant Energy System (CERES) instrument and the reflective solar bands (RSB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument, both onboard the NOAA-20 satellite, against the CPF benchmark measurements. The aimed intercalibration methodology uncertainty for both the target instruments is 0.3%. To achieve this meticulous intercalibration accuracy, the CPF team has formulated methods to mitigate the impacts of spatial, spectral, and angular differences between the intercalibration footprints from the CPF and target instruments. The CPF team will also employ Polarization Distribution Models (PDMs) to characterize the polarization state of the Earth-reflected radiance as a function of the intercalibration footprint scene type, solar and viewing geometry, and wavelength. The PDMs will assist in identifying low-polarized scene radiances for rigorously calibrating the polarization-sensitive VIIRS instrument against the significantly-less polarization-sensitive CPF instrument. This paper will highlight the CPF mission overview and intercalibration approach, as well as other potential outcomes of the CPF intercalibration studies that may benefit the broader remote sensing community.
CLARREO Pathfinder as a Next-generation On-orbit Reference Standard for Reflective Solar Intercalibration
NASA’s Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) mission consists of a high-accuracy reflected solar (RS) spectrometer that will measure the Earth-reflected solar radiation from International Space Station with an SI-traceable radiometric uncertainty of 0.3% (1-sigma). The CPF measurements will serve as an on-orbit reference for intercalibrating other spaceflight RS instruments. The CPF intercalibration team has designed a state-of-the-art approach to calibrate the shortwave channel (300-5000 nm) of the Clouds and the Earth’s Radiant Energy System (CERES) instrument and the reflective solar bands (RSB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument, both onboard the NOAA-20 satellite, against the CPF benchmark measurements. The aimed intercalibration methodology uncertainty for both the target instruments is 0.3%. To achieve this meticulous intercalibration accuracy, the CPF team has formulated methods to mitigate the impacts of spatial, spectral, and angular differences between the intercalibration footprints from the CPF and target instruments. The CPF team will also employ Polarization Distribution Models (PDMs) to characterize the polarization state of the Earth-reflected radiance as a function of the intercalibration footprint scene type, solar and viewing geometry, and wavelength. The PDMs will assist in identifying low-polarized scene radiances for rigorously calibrating the polarization-sensitive VIIRS instrument against the significantly-less polarization-sensitive CPF instrument. This paper will highlight the CPF mission overview and intercalibration approach, as well as other potential outcomes of the CPF intercalibration studies that may benefit the broader remote sensing community.