As highlighted previously, the Level-0 initial processing, performed to preserve the integrity of the acquired data, occurs in real-time (i.e. in parallel to data reception). By contrast, Level-0 consolidation and downstream processing activities (i.e. to Level-1) are delayed until triggered by the recovery on-ground of the ancillary data. This occurs at the end of every satellite pass. Ancillary data are ingested together with the MSI raw data at the beginning of the Level-0 consolidation processing collates and appends all necessary metadata required for archiving and onward processing to Level-1.
- Level-0 viewing model initialisation: This processing step computes the viewing model for generation of the Preliminary Quicklook (PQL)
- PQL processing: This step includes the PQL resampling and the computation of ancillary data for the consolidated Level-0 product
- Preliminary cloud mask processing: This processing step generates the cloud mask from the PQL based on spectral criteria
- PQL compression: Performs the compression of the PQL
The position of these initial processes can be seen in the middle of Figure 1, up to the output block named Level-0 (Consolidated).