On-orbit calibration performance of Sentinel-3A OLCI referencing to SNPP VIIRS: 2-year result

The on-orbit calibration performance of the Ocean and Land Colour Imager (OLCI) onboard the Sentinel-3A satellite, launched on 16 February 2016, is evaluated via a radiometric intersensor comparison referencing to SNPP VIIRS. Among the 21 OLCI bands, which are reflective solar bands (RSBs), seven of the bands match up spectrally with the seven shortest wavelength SNPP VIIRS bands. The radiometric comparison utilizes a "nadir-only" refinement of the simultaneous nadir overpass (SNO) approach for analysis. The time series result for OLCI bands Oa02, Oa03, Oa08 and Oa17, which well spreads out over the spectral range of OLCI, shows a two-year stability at the level of 0.3% that supports nominally correct on-orbit calibration for Sentinel-3A OLCI. The result for Oa08, Oa09 and Oa10, the three spectrally adjacent bands matching to SMPP VIIRS Band M5, demonstrates the impact of spectral mismatch - different radiometric ratio baselines and seasonally modulating patterns.