MTG-I Flexible Combined Imager signal flow

The Meteosat Third Generation Imager satellites carry two completely new instruments, a Flexible Combined Imager and Europe’s first Lightning Imager, to deliver high-quality data for better weather forecasting.

The animation shows the direction of the light from Earth through the Flexible Combined Imager’s front telescope optics. The first mirror (M0) is mounted on the scan mechanism and is just a flat mirror which can be moved to allow the full Earth disc to be scanned. The second mirror (M1) is the first fixed mirror that is concave and reflects a convergent beam towards the much smaller third mirror (M2). The M2 is mounted on the refocusing mechanism, which by moving the mirror a few microns, will allow a better focus of the image if required.

From M2 the beam then travels toward the fourth element and on-route passes through the calibration and obscuration mechanism which can be orientated either to block the beam (in case of risk of direct Sun impingement) or to place a filter element in the beam during Sun calibration. During normal operations, this mechanism provides free passage of the beam with no additional optical element. The final mirror is the M3 which then focuses the beam into the spectral separation assembly which through a series of frequency specific coatings on the mirrors and dichroic plates splits the beam into the four spectral bands UV/VIS, IR1, IR2 and IR3. These beams are then directed into the cryostat where four detector assemblies are mounted. Here, the detector assemblies are cooled to –220C to ensure optimum performance.