Level-1 processing uses consolidated Level-0 data as input.
- Level-1A processing is focused on decompressing relevant mission source packets. The Level-1A product is not available to Users.
- Level-1B processing uses the Level-1A product and applies the required radiometric corrections. The Level-1B product is not available to Users.
- Level-1C processing uses the Level-1B product and applies radiometric and geometric corrections (including orthorectification and spatial registration).
The Level-1B processing sequence is broken down into the following steps:
- Level-1B radiometric processing, including:
- dark signal correction
- pixel response non-uniformity correction
- crosstalk correction
- defective pixels identification
- high spatial resolution bands restoration (de-convolution and de-noising). This correction is disabled by default in the Level-1B processing.
- binning of the 60 m spectral bands.
- adding of the radiometric offset.
- Resampling on the common geometry grid for registration between the Global Reference Image (GRI) and the reference band (B4 by default).
- Collection of the tie-points from the two images for registration between the GRI and the reference band.
- Tie-points filtering for image-GRI registration: filtering of the tie-points over several areas. A minimum number of tie-points is required.
- Refinement of the viewing model using the initialised viewing model and and Ground Control Points (GCPs). The output refined model ensures registration between the GRI and the reference band.
- Level-1B imagery compression utilises the JPEG2000 algorithm.
Level-1C processing includes radiometric and geometric corrections including ortho-rectification, add of the radiometric offset and spatial registration on a global reference system with sub-pixel accuracy.
Level-1C processing is broken down into the following steps:
- Tiles association: selection of pre-defined tiles intersecting the footprint of the required image.
- Resampling grid computation: enabling linking of the native geometry image to the target geometry image (ortho-rectified).
- Resampling of each spectral band in the geometry of the ortho-image using the resampling grids and an interpolation filter. Calculation of the TOA reflectances also occurs in this step.
- Quality masks computation in raster format: MSK_CLASSI (opaque cloud, cirrus and snow), MSK_QUALIT (lost ancillary packets, degraded ancillary packets, lost MSI packets, degraded MSI packets, defective pixels, no data, partially corrected crosstalk, and saturated pixels) and detector footprints masks are generated.
- Imagery compression of the resultant Level-1C imagery via the JPEG2000 algorithm