Gain is a measure of amplification, expressed in dB. Each of the spectral channels can be operated at one of 16 different gain levels (0–15).
These gain levels are used to obtain the optimum dynamic range (0–255) for each spectral channel and are adjusted as required.
The image gain level adjustment is particularly useful for compensating for the effects of radiometer contamination and detector ageing.
At the start of operations of a particular satellite the gain level is selected for each spectral channel such that saturation, i.e. instances of counts of 255, either does not occur, or is very infrequent.
Since the gain steps have an approximate ratio of 1.2, an increase of gain would normally be made when the maximum count at local noon falls to less than 212.
In general, the user should not be concerned with the image gain changes, in terms of calibration, since the effects of any gain change will be compensated for by an adjustment of the operational calibration coefficients. For calibration information, please see the Calibration pages.
The information below shows the electronic gain settings for the one operational first generation EUMETSAT satellite. Historical gain settings for Meteosat-2 to Meteosat-7 are also available.
Current gain figures for Meteosat First Generation
- VIS1+2: 5
- WV: 5
- IR: 5
Most recent gain change: 23 March, 2011
- VIS1+2: 6
- WV: 12
- IR: 11
Most recent gain change: 15 July, 2014
The following historical gain settings are available to download: