The Ocean Land Color Imager (OLCI) aboard the European Space Agency's (ESA's) Sentinel-3 satellite series is a key mission driver for the platform, providing continuity with the instrument capability of the ENVISAT MERIS sensor flown previously and abruptly ended in 2012. The OLCI is a push-broom type imaging radiometer with 21 bands ranging from 400 to 1200 nm that overlap with the Sea and Land Surface Temperature Radiometer (SLSTR) sensor, on the same platform, allowing for the fusion of the two instruments. The OLCI has 5 cameras, and is able to avoid sun glint by pointing these cameras in a slightly westerly direction.
There are three modes of level 1 processing. The OL_1_ERR product comes from the Earth Observation (EO) mode at reduced-resolution (RR). In this mode the L1B products provide calibrated, geolocated, and spatially resampled top of atmosphere (TOA) radiance for all 21 OCLI bands. For a nominal orbit, the reduced-resolution product has approximate pixel size of 1.2km at the sub-satellite point.
The OLCI is always operated in full-resolution (FR) mode over both land and ocean. However, the data are processed in RR mode, unless charted land is within a 300 km range of the nominal swath. The OLCI RR products are generated by averaging the signal of 16 full spatial resolution pixels (four adjacent pixels across track for four successive pixel lines along track), resulting in a product that is one-quarter the resolution of the FR product.
For details of Level-1B processing, see the technical guide on L1B processing.