MTG-I1

For the first time over Europe and Africa, the Lightning Imager (LI) provides real-time data on the location and intensity of lightning flashes.

Data from the Lightning Imager will enable more precise forecasts of severe thunderstorms.

The imager detects all types of lightning: cloud-to-cloud, cloud-to-ground and intra-cloud flashes, thus providing an advantage over ground-based lightning detection networks. The LI is a new instrument on Meteosat, it has no heritage from the Meteosat Second Generation series.

The LI uses detector elements arranged in a detector array covering the whole Earth (no scanning mechanism).

The total energy received from the photons are sensed by each detector element and integrated during the integration period. These are then compared with the LI trigger threshold and if the energy exceeds this threshold, it is identified as an LI triggered event (Figure 1).

Figure 1: LI triggered event

The Lightning Imager (LI), on board the MTG-I satellites, will continuously measure at a wave-length of 777.4nm with a very narrow bandwidth, with a spatial resolution 4.5km at sub-satellite point, triggered by a variable threshold — optical pulses initiated by lightning emitting energy of larger than between 4 and 7µJm-2sr-1.

The field of view (FOV) (Figure 2) of the LI instrument is covered by four identical cameras on the instrument, each covering one out of four domains on the observable Earth disc.

Figure 2: Field of view of the Lightning Imager instrument

Products derived from the instrument data will be arranged around following three categories:

Events — what the instrument measures, a triggered pixel in the detector grid.

Groups — neighbouring events in the same integration period (1 ms), representing a lightning stroke.

Flashes — collection of groups in temporal and spatial vicinity (XXkm, YY milliseconds), representing a lightning flash.

The MTG-I LI instrument will complement the NOAA Geostationary Lightning Mapper (GLM) on the GOES-R and the GOES-S satellites and CMA Lightning Mapper onboard the FY-4 satellite series.

Figure 3: LI product categorisation

FCI, on the MTG-I satellite, will continue the very successful operation of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on Meteosat Second Generation (MSG). Requirements have been formulated by regional and global numerical weather prediction (NWP) and nowcasting communities.

These requirements are reflected in the design which allows for scanning the full Earth disc in 10 minutes in support of the full disc scanning service (FDSS), or the upper quarter of the disc (i.e., Europe) in 2.5 minutes in support of the rapid scanning service (RSS).

The FCI measures in 16 channels in the visible and infrared spectrum of which eight are placed in the solar spectral domain between 0.4µm to 2.2µm, delivering data at a 1km spatial sampling distance (resolution) at nadir (sub-satellite point the centre of the disc). The additional eight channels are in the thermal spectral domain between 3.8µm and 13.3µm, delivering data at 2km spatial sampling distance at nadir. This observation mode is referred to as full disc high spectral resolution imagery (FDHSI) mission.

Furthermore, the FCI samples two channels in the solar domain (0.6µm and 2.2µm) at higher spatial sampling distance of 0.5km. and two channels in the thermal domain (3.8µm and 10.5µm) at higher spatial sampling distance of 1km at nadir. This observation mode is referred to as high spatial resolution fast imagery (HRFI) mission.

With both missions, the FCI instrument supports the full disc scanning service (FDSS) and the rapid scanning service (RSS).

With the FCI on board the MTG-I satellites, Europe will continue to play the leading role in imaging radiometry from the geostationary orbit in the decades to come.