Collocated Sentinel-3 OLCI and SLSTR reflectance imagery

The S3 4Sci Snow research project is gaining momentum, now with scripts that enable batch processing of two important steps: 1.) collocating OLCI and SLSTR imagery, that is, aligning pixels to a common geographic grid and 2.) converting the imagery to top of the atmosphere reflectance.


(above, 22 August 2016 southern Greenland Sentinel-3 scene of TOA reflectance from OLCI band 21, 1020 nm). In this part of the optical spectrum we find strong reflectance differences between fresh snow cover, melting snow and bare ice (dark areas).

The processing chain the project follows is illustrated below. The collocation happens as OLCI and SLSTR radiances are combined.


Sentinel-2 at the Lautaret site

The col du Lautaret site, located in the heart of the French Alps, is used by the team as a validation target for the “ESA SEOM Sentinel-3 for Science Land Study: Snow S-3-Snow”” project. The site is host to numerous observations of the snowpack and the atmosphere which will be used as part of this contract, in parallel with other CNRS / Météo France funded projects.
To account for the evolution of the snowpack a good repetitiveness of observations is necessary, therefore automated ground measurements are carried out during the winter season. Additionally, Sentinel 2 (L1C) data is being used as a inter-comparison tool, to test methods that will be applied to Sentinel 3 imagery.


Above, a time-series animation from Sentinel-2 images aquired over the winter 2016-2017 (Maxim Lamare).