Conversion to Radiances
So far, all processing relating to the visible, near-infra-red, and short-wave channels has been carried out using calibrated reflectances*.
This processing is applied to convert calibrated reflectances computed at the first stage of the Level-1B processing into radiances. For this purpose, it uses the seasonally adjusted solar irradiance computed at Level-1A.
* In fact calibrated "reflectances" are improperly named but kept for historical reasons, linked to AATSR. "Normalised radiances" would have been more appropriate since data are not corrected for the cosine of the solar zenith angle while applying calibration coefficients to numerical counts outputs by SLSTR.