Lightning Imager First Data, A New Eye On Lightning Storms

Launched atop an Ariane 5 from the Guiana Space Center in Kourou, French Guiana, on December 13, 2022, the first Meteosat Third Generation (MTG) satellite is making significant steps toward full operational capabilities. Lighting Imager, the first-ever instrument capable of continuously detecting Lightning Storms, has entered service with the first calibration dataset released today, July 03, 2023.

*North and Central Europe seen by Lightning Imager north camera. Credits: ESA / EUMETSAT*

The First Data Release

ESA and EUMETSAT just released a set of twenty animations. Each animation is a minute-long video featuring the lightning measurements from Lightning Imager, overlaid with a black-and-white image produced by the instrument.

North camera showing storms over north and central Europe. Credits: ESA / EUMETSAT

The north camera captured the frames shown above during a window spanning from June 8 to June 11, 2023. Local thunderstorms appear mainly in the afternoon and sunset due to the storm generation mechanism, as the Sun releases most of the energy during the daytime. In the evening and nighttime, these phenomena quickly dissipate due to the unavailability of a heat source.

East Camera tracking a storm in the Sahel region. Credits: ESA / EUMETSAT

Another interesting video is the one shown here, The Sahel. This animation, produced by the east camera during a thirteen hours time window on June 6, proves the instrument’s capability of tracking in close-up view a single system. Specifically, a convective system is captured during its westward movement in the Sahel region of northern Africa. Two fascinating aspects: first, we can see how thunderstorms are mainly generated from midday to evening. Secondly, most of the events occur on the storm system’s edge. Sun glint can also be seen entering the FoV of the instrument, proving the capability of Lightning Imager to work under all ambient conditions.

“The animations show the instrument’s ability to accurately and effectively detect lightning activity over the whole area of the cameras’ field of view, which covers 84% of the Earth disc.”

— Simonetta Cheli, Director of Earth Observation Programmes at ESA

Detecting lightning from space is not an easy task

Developed and built by Thales Alenia Space and Leonardo in Italy, Lighting Imager is an ensemble of four telescopes working in the near-infrared light spectrum (wavelength of 777.4 nm). Each telescope has an aperture of 110 mm, a Field of View (FoV) of 4.75 deg, and features a set of five lenses. A CMOS detector (1000 x 1170 pixels) capable of acquiring 1000 frames per second is placed at the end of each telescope. The four FoVs slightly overlap, granting complete coverage of Europe, Africa, and a portion of South America.

On the left: Lighting Imager 3D model. On the right: the four telescopes’ FoV with overlapping regions. Credits: Proceedings of International Conference on Space Optics - ICSO 2012 - Optical design of the lightning imager for MTG — On the left: Lighting Imager 3D model. On the right: the four telescopes’ FoV with overlapping regions. Credits: Proceedings of International Conference on Space Optics – ICSO 2012 – Optical design of the lightning imager for MTG

Detecting a lighting event poses a challenging task; first of all, the instrument shall be capable of precisely identifying a lighting flash no matter the light condition (both during sunlight and nighttime). Moreover, the Lighting Imager must operate in different environmental conditions, such as land, desert, ocean, and under cloudy or free skies. For this reason, a series of filters and a specific electronic device capable of adjusting the detection threshold are installed onboard.

Let’s see now how the instrument works. In the presence of lightning, the detection event starts when a triggered pixel is measured on the sensor; during the same integration period (1ms given the 1000 image per second frame rate), the neighboring pixels are evaluated, looking for more triggered pixels to be included in the group. Lastly, the flashes are retrieved by considering different groups in time and spatial vicinity.

The onboard image processing also plays a significant role; the instrument can generate approximately 48 Gbps of data, of which little less than 30 Mbps can be transmitted to the ground. An AI-based processing algorithm is adopted to discard false detections and compress the images, dramatically reducing the amount of data transferred.

MTG, enhancing Europe’s weather forecast capabilities

Meteosat Third Generation is a satellite constellation of four MTG-I imager satellites and two MTG-S sounding satellites, divided into two groups of three. The spacecraft, placed in Geostationary Orbit, have been designed and built by a consortium of European companies led by Thales Alenia Space and OHB. EUMETSAT instead carries out operations in collaboration with Telespazio. The program aims to enhance Europe’s weather forecasting capabilities, specifically in the storm prediction sector. The measurements coming from the six satellites will give forecasters a real-time storm-tracking capacity, dramatically improving the accuracy of weather predictions.

*MTG constellation made of two Imagers and one Sounding satellite. Credits: ESA*

“Severe storms are often preceded by abrupt changes in lightning activity. By observing these changes in activity, Lightning Imager data will give weather forecasters additional confidence in their forecasts of severe storms. [-] When these data are used in conjunction with the high-resolution data from the Flexible Combined Imager, weather forecasters will be better able to track the development of severe storms and have a longer lead-in time to warn authorities and communities.”

— Phil Evans, Eumetsat Director General