MSG-SEVIRI solar channels are calibrated against the MODIS instrument following the methodology outlined in Meirink et al. (2013). This calibration has been extended to the full MSG era and updated using Aqua-MODIS Collection 6.1 reflectances as a reference.
The figure below shows the resulting calibration slopes, for which the months April and October of each year have been considered (symbols). Linear trend fits are shown by the solid lines, and the coefficients of these fits are indicated (D - D1/1/2000 denotes the number of days since the beginning of 2000). The EUMETSAT operational calibration slopes are shown by dashed lines.
Meirink, J.F., R.A. Roebeling and P. Stammes, 2013: Inter-calibration of polar imager solar channels using SEVIRI, Atm. Meas. Tech., 6, 2495-2508, doi:10.5194/amt-6-2495-2013