Minimize VIS and SWIR Radiances

The SLSTR Level-1B products for the visible/NIR/SWIR channels (labelled as S1 to S6 channels) gather, for each view and for each channel, the full-resolution, geolocated, radiometric measurements expressed as TOA radiances.

The radiometric measurements are indexed according to the across track and along track direction on a 0.5 km grid. Two detector stripes are defined, labelled A and B. The B stripe is only present for the SWIR channels, i.e. channels S4 to S6.

The radiances associated with each image and orphan pixel, projected on the 500 m grid, are included in the SLSTR Level-1B product, in a specific file named:

  • S[1:6]_radiance_an/o.nc for channels S1 to S6, nadir/oblique view and A stripe.
  • S[4:6]_radiance_bn/o.nc for channels S4 to S6, nadir/oblique view and B stripe.

These files also include the exception flags associated with each radiance measurement.

In addition to radiances, several annotation data are included in SLSTR Level-1B products and provide additional information:

  • S[1:6]_quality_a/bn.nc and S[1:6]_quality_a/bo.nc (for nadir and oblique view respectively) gather, for each solar channel, information concerning the detector filter band centre and bandwidth, and the black body radiance noise.
  • flags_a/bn.nc and flags_a/bo.nc gather flags concerning cloud presence (based on the threshold tests and the Bayesian probability test), sun glint, pixel properties and scan and flip errors for each selected stripe (stripe A is always present as it is the dedicated stripe for S1 to S3).
  • indices_a/bn.nc and indices_a/bo.nc provide for each pixel on the selected 500 m grid, their coordinates on the instrument grid (scan, detector and pixel number and similar parameters for orphan pixels).
  • geodetic_a/bn.nc and geodetic_a/bo.nc provide for each pixel on the selected 500 m grid, their geographical coordinates (latitude, longitude and altitude and similar parameters for orphan pixels).
  • cartesian_a/bn.nc and cartesian_a/bo.nc provide for each pixel on the selected 500 m grid, their ortho-geolocated, quasi-cartesian coordinates (x,y), where x is defined as the across track distance on the ellipsoid, locally perpendicular to the sub-satellite track, and y as the distance along the sub-satellite track. Similar parameters are also included for orphan pixels.
  • time_a/bn.nc provides the measurement times of each line, in addition to specific parameters allowing retrieval of the acquisition time of each instrument pixel.

Note: in addition to these annotation data files, additional files provide information on the 16 km tie-point grid, giving the solar and viewing angles, the cartesian and geodetic coordinates and meteorological parameters. Visible calibration coefficients, used in the processing of the SWIR, NIR and visible channels, are also provided in a specific file, named viscal.nc.