Minimize TIR Brightness Temperature (BT)

The SLSTR Level-1B products for the thermal IR and fire channels (labelled as S7 to S9 and F1, F2 for fire channels) contain, for each view and for each channel, the full-resolution geolocated radiometric measurements, expressed as Top of Atmosphere (TOA) Brightness Temperatures (BT).

The radiometric measurements are indexed according to the across track and along track direction on a 1 km grid. The brightness temperature associated with each image and orphan pixel, defined on the 1 km grid, is contained in a specific file named:

  • S[7:9]_BT_in.nc for channels S7 to S9 and for nadir view
  • S[7:9]_BT_io.nc for channels S7 to S9 and for oblique view
  • F[1]_BT_fn/fo.nc for fire channels F1 for nadir or oblique view
  • F[2]_BT_in/io.nc for fire channels F2 for nadir or oblique view

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

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

  • S[7:9]_quality_in.nc and S[7:9]_quality_io.nc (for nadir and oblique view respectively) contain information concerning the detector filter band centre and bandwidth, the calibration parameters, and the black body noise equivalent brightness temperature. The same is true for fire channels in the F[1;2]_quality_in/o.nc files.
  • flags_in/o.nc gathers flags concerning cloud presence (based on the threshold tests and the Bayesian probability test), sun glint, pixel properties and scan and flip errors.
  • indices_in/o.nc provides, for each pixel on the 1 km grid, the coordinates on the instrument grid (scan, detector and instrument pixel number and similar parameters for orphan pixels).
  • geodetic_in/o.nc provides for each pixel on the 1 km grid, the geographical coordinates (latitude, longitude and altitude and similar parameters for orphan pixels).
  • cartesian in/o.nc provides for each pixel on the 1 km grid, the ortho-geolocated quasi-cartesian coordinates x and 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_in/o.nc provides the measurement times of each line, in addition to specific parameters allowing the 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.