Level-2 FRP

Sentinel-3 SLSTR Level-2 FRP product type

Starting on 15th January 2020, the SLSTR Level-2 FRP product is providing one measurement data file, FRP_in.nc, with Fire Radiative Power (FRP) values and associated parameters generated for each fire detected over land and projected on the SLSTR 1 km grid.

The fire detection is based on a mixed thermal band, combining S7 radiometric measurements and, for pixels associated with a saturated value of S7 (i.e. above 311 K), F1 radiometric measurements.

Since 28th February 2022, FRP product is also including a second file providing several fire characteristics for all fires detected using SWIR S5 and S6 radiometric measurements. This detection is performed over both Land and Ocean surface but only during night-time. This second file is providing the location of the detected fires on the SLSTR 500m grid and, depending on the used SLSTR stripe, is called FRP_an.nc or FRP_bn.nc. The SWIR FRP is associated when possible with the equivalent MWIR FRP, using a clustering approach.  

A number of annotation data file including information in support of the measurement data files on the 1 km grid is also provided.

The measurement data files include:

  • FRP and its uncertainty. As described above, fires can be detected using thermal radiometric measurements (over land) or using SWIR radiometric measurements (Over both land and ocean but only during nighttime). FRP can be then computed using TIR or MWIR radiometric measurements, in agreement with the used detection strategy.
  • TCWV above fire
  • Total atmospheric transmittance
  • projected area of detector IFOV on surface
  • glint angle (i.e. the angle between nadir view and specular direction)
  • associated across and along track coordinates
  • associated time and geographical coordinates
  • hotspot classification code
  • background window size
  • flags and contextual information such as proportion of cloudy or water pixels in the background window, Fire pixel radiance, …

The annotation data sets is similar to the SLSTR L1b products and includes meteorological annotations, cartesian and geodetic coordinates associated with the radiometric measurements and to the tie-points grid defined for SLSTR, geometry information and quality flags.

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