Ariane 6 Launches Advanced Weather Satellite

Arianespace has launched the Ariane 6 rocket, placing the 3.8-tonne MTG-I2 weather satellite into orbit from Europe's Spaceport in Kourou, French Guiana. The mission, described step-by-step by engineers from ArianeGroup, Arianespace, CNES, Eumetsat, ESA, and Thales Alenia Space, represents a milestone for European space technology aimed at improving Earth observation for disaster monitoring.

The rocket was built on the premise of being cheaper and more versatile than its predecessor, the Ariane 5, to compete in today's international environment. Its core stage was manufactured and tested in France, while the upper stage was built in Germany. Both arrived in Guiana already "ready to fly," transported by the dedicated cargo ship Canopée.

The Launcher's Assembly and Fueling

The solid-fuel boosters, however, are manufactured locally in French Guiana at the Regulus and Europropulsion plants. Engineers stated it is more practical to make them there than to ship that type of propellant from Europe. Once all components are on site, the ArianeGroup team needs only seven to nine days to assemble the launcher's central core.

Fueling is a precise operation. "It is not like pulling up at a petrol station, filling the tank and driving off," said deputy launch director Frédéric. Filling the launcher takes two hours, followed by another hour and a half for thermal stabilisation, because the liquid oxygen is at about -150°C and the liquid hydrogen at -250°C.

The MTG-I2 flight featured two rare technical firsts for Ariane 6. It was the vehicle's first flight to a geostationary transfer orbit (GTO), the most distant orbit reached so far, in its A62 configuration with two side boosters. It also operated with a launch window of two hours and 30 minutes instead of a fixed instant, providing flexibility to handle issues.

The rocket's upper stage, powered by the Vinci engine, can be re-ignited in mid-flight thanks to a helium pressurisation system. This capability, which Ariane 5 did not have, settles the propellant before each re-ignition.

Horizontal Rocket Assembly

The Ariane 6 is assembled horizontally, not vertically. Guided vehicles move the lower and upper stages into position, where they are joined with a tolerance of barely a millimetre. Engineers stress the process is assisted, not fully automatic, requiring staff to check and validate many steps.

From the moment the two stages arrive, it takes around ten days until the central core is ready for the pad. The facility has two parallel assembly lines, allowing work on the next rocket to begin as soon as the previous one leaves. The program aims for a cadence of nine to ten launches per year from 2027.

Preparing the Sensitive Satellite Payload

A few metres away, in the encapsulation building, air is filtered and its temperature and humidity are finely regulated. This is the last room where technicians have direct physical access to the satellite before it is sealed inside the rocket's fairing. For the MTG-I2 optical meteorological instrument, which is extremely sensitive to contamination, this cleanliness is critical.

The process includes light traps for insects and birds. When the satellite container arrives at night and the building's doors open, any animal slipping inside could jeopardise the payload. "We cannot just open the container and let it out with a bird inside, obviously," explained one facility manager who coordinated the final campaign stretch.

Launch Control and Weather Veto

Eleven hours before lift-off, control shifts to the Júpiter control room at CNES. A large screen shows system statuses in green, the planned trajectory, and countdown clocks. Launch operations director Maxime André coordinates safety across the entire range and, with the quality team and measurements officer, provides the final go-ahead.

The mission team remains in contact with the satellite's own control centre, located some four kilometres away, to confirm everything remains nominal right up to the last minute.

Weather is a final hurdle. Meteorological analyst François Laforge monitors lightning and wind most closely. The criteria are strict: no storm within a ten-kilometre radius, and no cloud above 6,500 metres in that radius, as a rocket passing through such a high cloud can generate static electricity and trigger lightning.

Radars measure cloud height while a triangulation system of three antennas pinpoints every electrical discharge in real time. Weather balloons with radiosondes, launched during the countdown, measure the wind profile at altitude. Flight safety engineer Leonard Bouchaillot uses this data to ensure the pre-calculated "launch corridor" remains valid, a requirement of French space law for public safety. The final weather check comes barely ten minutes before lift-off.

The Programme's Scale and Purpose

James Champion, head of the MTG project at ESA, outlined the 16 years of work on the Meteosat programme. It involved almost two decades of anticipating technology that did not yet exist. The programme cost around 6 billion euros in today's economic conditions, while its benefits exceed 61 billion once infrastructure is considered, not to mention lives saved by data that can trigger evacuation plans.

With the satellite hours from orbit, Cristian Bank, director of programme preparation at Eumetsat, set the launch in the context of a continent increasingly hit by extreme weather. He noted losses of 10 billion euros a year in damage and thousands of deaths in Europe over the past five years. The MTG-I2 satellite will provide a watchful eye over Europe every 2.5 minutes, key to forecasting and preventing adverse events.