Minimize TIR Brightness Temperature (BT)

The SLSTR Level-1B product is generated during observation and joint processing mode and mainly contains the TIR Brightness Temperature (BT).

The SLSTR Level-1B TIR BT product gathers, for each view and for each channel, the full-resolution geolocated radiometric measurements. For thermal IR and fire channels (labelled as S7 to S9 and F1, F2 for fire channels), the radiometric measurements are expressed in Top of Atmosphere (TOA) brightness temperatures.

The radiometric measurements are indexed according to the across track and along track direction on a 1 km grid. The brightness temperature associated to each image and orphan pixel, defined on the 1 km grid, is also included in the SLSTR Level-1B product, 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;2]_BT_in/io.nc for fire channels F1 and F2 for nadir or oblique view.

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

In addition to brightness temperatures, several annotation data are included in SLSTR Level-1B products and provide additional information related to the radiometric measurements.

  • S[7:9]_quality_in.nc and S[7:9]_quality_io.nc (for respectively nadir and oblique view) gather, for each TIR channel, information concerning the detector filter band centre and bandwidth, and the black body noise equivalent brightness temperature. The same is true for fire channels in the F[1;2]_quality_in/o.nc file.
  • in the frame of coming evolutions, a file gathering all parameters computed during stray Light correction will also be produced
  • flags_in/o.nc gathers flags concerning cloud presence (based on current tests and Bayesian probability), sun glint, pixel properties and scan and flip errors.
  • indices_in/o.nc provides for each pixel on the 1 km grid, their coordinates on the instrument grid (scan, detector and number and similar parameters for orphan pixels)
  • geodetic_in/o.nc provides for each pixel on the 1 km grid, their 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, their 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 that in addition to these annotation data files, some files provide information on the 16 km tie-point grid as solar and viewing angles, the cartesian and geodetic coordinates and meteorological parameters. Visible calibration coefficients, used in the processing, are also provided in a specific file named viscal.nc.