Calibration of the DSCOVR EPIC Visible and NIR Channels using Multiple LEO Radiometers

The first five years of operation the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) at Lagrange one point have produced results that uniquely complement data from currently operating low orbit Earth-observing instruments. In this paper we describe an updated unified approach to EPIC calibration. approach, calibration coefficients and their trends were obtained by comparing observations measurements polar orbiting radiometers. study L1B reflectances Moderate Resolution Spectroradiometer (MODIS) onboard Aqua Terra satellites, Multi-angle (MISR) Visible Infrared Radiometer (VIIRS) Suomi National Polar-orbiting Partnership (Suomi NPP) spacecraft used infer for four visible near-infrared channels: 443 nm, 551 680 780 nm. Version three made between June 2015 August 2020 comparison. procedure identifies most homogeneous radiometer scenes matching scattering angles are temporarily spatially collocated with observations. These determine reflectance count (R/C) ratios in spectrally analogous channels. Seasonal average R/C analyzed obtain gains trends. full dataset period not statistically significant except nm channel. No changes found after instrument’s exit safe hold March 2020. also differences resulting separate calibrations: against MODIS or Terra, as well forward aftward MISR cameras. Statistical tests indicate two datasets channels where Aqua-derived may be around 2% lower compared Terra. dependence on instrument angle DSCOVR-Earth distance investigated. Lastly, model Low Orbit (LEO) calculated match viewing geometry employed how depend EPIC-LEO differences. effect LEO angular mismatch was shown small.