Inside Kourou: how a satellite is readied to watch Europe's skies and prevent natural disasters
Engineers from ArianeGroup, Arianespace, CNES, Eumetsat, ESA and Thales Alenia Space describe, step by step, how an Ariane 6 rocket and a 3.8-tonne weather satellite were brought together to the launch pad at Europe's Spaceport.
After two flights and more than 7,000 kilometres from Paris, we have witnessed first-hand a launch that has put Europe at the forefront of global space technology: the placing in orbit of a state-of-the-art satellite that speeds up mapping of the Earth’s surface to monitor disasters and help prevent floods and fires from continuing to devastate countries across the Old Continent.
The heart of the Ariane 6 launch system is not on the pad, but in a windowless control room several kilometres away. That is where we are received by the deputy launch director, Frédéric, whose surname we are withholding to protect him from cyberattacks, and several engineers who walk us through the details of the milestone. The rocket that is about to place the new European weather satellite in orbit was built on a very specific premise: to be cheaper and more versatile than its predecessor, Ariane 5, in a far more competitive international environment than a decade ago.
The launcher: a rocket designed not to waste time in Kourou
The key, the engineers explain, lies in where each task is carried out. The Ariane 6 core stage is manufactured and fully tested in France; the upper stage in Germany. Both arrive in Guiana already "ready to fly", with no need for any further functional tests once they are unloaded from the Canopée. Transport is handled by the dedicated cargo ship Canopée, the same one with the large sails that made the shipping line famous, which also picks up parts in Bordeaux and Rotterdam before completing the route to South America.
The solid-fuel boosters that assist at lift-off, by contrast, are manufactured in French Guiana itself, at the Regulus and Europropulsion plants. "It is much more practical and convenient to manufacture the boosters here than to ship that type of propellant from Europe," the engineers sum up. Once all the pieces are on the ground, the ArianeGroup team needs only between seven and nine days to assemble the launcher’s central core and have it ready to fly.
"It is not like pulling up at a petrol station, filling the tank and driving off. Filling the launcher takes two hours, and then another hour and a half of thermal stabilisation, because the liquid oxygen is at about -150°C and the liquid hydrogen at -250°C," Frédéric tells us.
The MTG-I2 flight also featured two rare technical characteristics. It was the first time an Ariane 6 had flown to a geostationary transfer orbit (GTO), the most distant orbit reached by the rocket so far, in its A62 configuration with two side boosters. And, for the first time since the maiden flight, the mission had a launch window of two hours and 30 minutes instead of a fixed lift-off instant, giving the team some leeway to deal with unexpected issues.
The rocket’s upper stage, powered by the Vinci engine, can also be re-ignited in mid-flight thanks to a helium pressurisation system, which settles the propellant at the bottom of the tank before each re-ignition: a capability Ariane 5 did not have and which Ariane 6 is debuting on this type of mission.
The build: robots assembling a rocket horizontally
The rocket is assembled horizontally, not vertically. Guided vehicles move the lower and upper stages into a common position, where the two pieces are joined with a tolerance of barely a millimetre. "It is not a fully automatic process, it is assisted: there are many steps that the staff have to check and validate before triggering the next automatic sequence," the experts stress.
From the moment the two stages arrive in the facility, it takes around ten days until the central core is ready to be moved to the pad. The facility has two parallel assembly lines, which makes it possible to start putting together the next rocket as soon as the previous one heads out to the launch platform. The goal of the programme is to reach a cadence of nine to ten launches a year from 2027.
The satellite: the most sensitive passenger ever to fly on an Ariane 6
A few metres away, in the encapsulation building, the air is filtered, temperature-controlled and its humidity finely regulated. It is the last room where technicians have direct physical access to the satellite before it is sealed inside the rocket’s fairing. For MTG-I2, an optical meteorological observation instrument that is extremely sensitive to contamination, that cleanliness is not a minor detail: any particle can degrade the quality of its future images.
The process even includes a system of light traps for insects and birds: when the container with the satellite arrives at night and the gigantic doors of the building open to let it in, any animal that slips inside could jeopardise the cleanliness of the payload. "We cannot just open the container and let it out with a bird inside, obviously," explains one of the managers of the facility, who has spent almost a year coordinating this final stretch of the campaign with the spacecraft team.
The Júpiter control room: the chain of command for the countdown
Eleven hours before lift-off, the final timeline begins and the centre of gravity shifts to the Júpiter control room at CNES, the French National Centre for Space Studies. A large operational screen shows the status of all systems in green, the planned trajectory and the countdown clocks.
In the centre sits Maxime André, the launch operations director, responsible for coordinating safety across the entire launch range (people, assets, environment) and, together with the quality team and the measurements officer who monitors telemetry, radar and tracking, providing the final voice and eyes that give the go-ahead.
Right up to the last minute, the mission team remains in contact with the satellite’s own control centre, located some four kilometres from the Júpiter room, to confirm that everything remains nominal and pass that confirmation up, step by step, to the operations director.
Lightning veto: the weather that can stop a launch
A few metres from the launch complex, a small team is watching the sky as closely as the engineers watch the rocket. François Laforge, meteorological analyst at the spaceport’s station, keeps his eye on two parameters above all others: lightning and wind. "Rain or temperature are not so important; what really matters are thunderstorms and wind, both at the surface and at altitude."
The criteria are strict: no storm within a ten-kilometre radius around the base, either during preparations or during lift-off itself; and no cloud above 6,500 metres in that same radius, because as the rocket passes through such a high cloud it can generate static electricity capable of triggering lightning. To monitor this, the team combines radars that measure cloud height with a triangulation system of three antennas that pinpoint every electrical discharge in real time.
Weather balloons with radiosondes, launched several times during the countdown, measure the wind profile at altitude, data that Leonard Bouchaillot, flight safety engineer, uses together with the rest of the team to ensure safe conditions so that the pre-calculated "launch corridor" – the zone where, for safety, a possible flight termination of the rocket is simulated – remains valid.
This, he explains, is a requirement set out in French space law to guarantee public safety. The final weather check comes barely ten minutes before lift-off. Once in the air, the risk changes in nature: the rocket passes the speed of sound in under 50 seconds and 50 kilometres in altitude in under two minutes, so wind very quickly ceases to be a real threat. The real risk, they insist, lies on the ground.
A 6-billion-euro programme with benefits topping 61 billion
James Champion, head of the MTG project at the European Space Agency (ESA), set out the 16 years of work on the Meteosat satellite programme. It has meant almost two decades anticipating technology that did not yet exist but had to be factored in when placing MTG-I2 in orbit.
The cost of the programme in today’s economic conditions has been around 6 billion euros, while its benefits exceed 61 billion, once infrastructure is taken into account, not to mention the number of lives that will be saved thanks to satellite data helping, for example, to trigger evacuation plans. This family of satellites will be key to forecasting and preventing adverse weather events.
The science: a watchful hawk’s eye over Europe every 2.5 minutes
With the satellite just hours away from being placed in orbit, Cristian Bank, director of programme preparation and development at Eumetsat, sets the launch in its real context: that of a continent increasingly hit by extreme weather events. "In the past five years we have seen losses of 10 billion a year in damage in Europe and thousands of deaths. Fortunately, the number of fatalities is falling as our forecasts and warnings improve, but the damage to infrastructure remains. We need to be more resilient," he warns.
MTG-I2 is the third part of a complementary trio: the first satellite, launched in 2022, offers a hemispheric view – Europe, Africa, the Atlantic as far as the Indian Ocean – feeding global weather models; the second, launched in 2025 and almost operational, measures the atmosphere in depth (humidity, temperature, wind, pressure); and the third, whose launch we have just witnessed, will focus on Europe and in particular the Mediterranean basin, which is heavily affected by adverse weather events, updating its data every two and a half minutes.
"That frequency is crucial for local weather forecasting in Europe and the Mediterranean, but also for civil protection: firefighters detecting forest fires, droughts, or Mediterranean tornadoes, which are becoming more frequent and more violent.
Bank estimates that the new satellite will need around half a year of commissioning before it can be integrated and calibrated with its two siblings. From then on, probably around April 2027, the three will operate as a single system.
The technical specifications: 500 million pixels every ten minutes
Graeme Mason, head of meteorological programmes at ESA, laid out the figures that make MTG-I2 one of the most advanced observation instruments ever placed in orbit. While the first satellite in the family scans the entire visible Earth disc every ten minutes at a resolution of 500 metres – around 500 million pixels per full sweep, distributed across 16 channels – MTG-I2 will focus solely on the upper quadrant centred on Europe, repeating the scan every 150 seconds.
Its second instrument, the lightning detector, operates in a very narrow band of the spectrum, the oxygen emission line at 777 nanometres, taking 1,000 samples per second. To resolve features 500 metres across from an orbit 36,000 kilometres above the Earth, the satellite needs extreme stability across its three axes.
This programme is an example of the strength of the European aerospace industry: with more than 17 European countries and 70 companies involved; over 200 subcontracts; and more than 2,200 people working on the project.
"This image generator is the best geostationary 'imager' in the world. The lightning detector is the best 'lightning imager' in the world, a technology that is ahead even of that of the United States. In ten years, ESA expects to send the next family of satellites to continue leading the way in monitoring and analysing the climate and its impacts.
Between the Ariane 6 control room, the satellite encapsulation facility and the weather station that tracks every cloud over Kourou, the launch of MTG-I2 has in fact been the sum of dozens of technical decisions taken by teams that rarely share the spotlight with the lift-off itself.
With this satellite in orbit, Europe completes the first operational trio of its third-generation meteorological constellation, a system that is set to support climate monitoring of the continent at least until well into the 2040s.
