Evaluation of systematic errors on polarization parameters from POLDER instrument data for use in CLARREO Pathfinder-VIIRS intercalibration

One of the Climate Absolute Radiance and Refractivity Observatory Pathfinder (CPF) mission’s science objectives is to intercalibrate the reflective solar bands of the NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) instrument against high-accuracy CPF measurements utilizing coincident, co-angled, and co-located footprints acquired over diverse Earth targets. To alleviate the effect of high polarization sensitivity of select VIIRS channels on intercalibration analysis, the CPF team will limit the intercalibration footprints over low-polarized scene types, which will be identified based on an empirical estimation of their degree of polarization (DOP) and angle of polarization (AOP) using Polarization and Directionality of the Earth’s Reflectance (POLDER) data. We describe the methodology for evaluating systematic errors in the estimation of DOP and AOP for Earth-reflected radiances using POLDER’s polarized bands and investigates their potential impact on CPF-VIIRS intercalibration uncertainty. The systematic errors were found to be <0.01 for DOP and <2.2 deg for AOP, which will have a negligible impact on CPF-VIIRS intercalibration uncertainty.