Signal calibration processing involves converting numerical counts into brightness temperature for the TIR channels, and into radiance in the case of the visible, NIR and SWIR channels.
Numerical counts are calibrated using calibration coefficients derived at Level-1A, either from the current orbit for the TIR and fire channels, or from the previous orbit via an auxiliary data file for the visible, NIR and SWIR channels.
This process is divided into two main steps:
- TIR channels calibration: converting digital counts for TIR channels, including Fire channels, to brightness temperature.
- Visible/NIR/SWIR channels calibration: converting digital counts for visible, NIR, and SWIR channels to reflectances.
Note: Reflectances will be converted to radiances as a final processing step, as the cloud identification step performs processing on brightness temperatures and reflectances.