The MERIS Level 1 Reduced Resolution (RR) product contains the Top of Atmosphere (TOA) upwelling spectral radiance measures at reduced resolution. The in-band reference irradiances for the 15 MERIS bands are computed by averaging the in-band solar irradiance of each pixel. The in-band solar irradiance of each pixel is computed by integrating the reference solar spectrum with the band-pass of each pixel.
The MERIS RR Level 1 product has Sentinel 3-like format starting from the 4th reprocessing data released to users in July 2020.
Each measurement and annotation data file is in NetCDF 4. The Level 1 product is composed of 22 measurements data files: 15 files containing radiances at each band (one band per file), accompanied by the associated error estimates, and 7 annotation data files.
The band-pass of each pixel is derived from on-ground and in-flight characterisation via an instrument model. The values "Band wavelength" and "Bandwidth" provided in the Manifest file of the Level 1 products are the averaged band-pass of each pixel over the instrument field of view.
The Auxiliary data used are listed in the Manifest file associated to each product.
MERIS was operating continuously on the day side of the Envisat orbit (descending track). RR data was acquired over 43.5 minutes in each orbit, i.e. 80% of the descending track.