In the facilities of the Cape Canaveral spaceport in Florida, the countdown has reached its final phase. The latest gem of European Earth observation technology, the Meteosat Third Generation Sounder satellite (MTG-S1), is safely housed within the fairing of a Falcon 9 launch vehicle. Everything is ready for the historic launch scheduled for tonight, July 1, at exactly 23:03 Central European Summer Time (CEST). This event represents the culmination of years of work and collaboration by hundreds of scientists and engineers across Europe, opening a new chapter in monitoring weather and air quality.

The past week was marked by frantic but meticulously coordinated final checks and preparations. One of the most significant moments was the encapsulation of the satellite within the rocket's protective fairing. This was the last time human eyes directly saw the satellite and the last opportunity for engineers to have any physical interaction with it, an emotional moment for the teams who have dedicated years to this project.

Final Steps on Earth: Mating and Protection

Before being hidden from view forever, MTG-S1 underwent a crucial operation – attachment to the launch vehicle adapter. This seemingly simple component plays a critical role; it is the physical and electrical link between the satellite and the rocket, ensuring stability against the incredible forces at play during liftoff. Equally important, this very adapter will enable the precise and safe separation of the satellite from the second stage of the launch vehicle when they reach the planned altitude on their way to geostationary orbit.

During these delicate maneuvers, the satellite was in a dormant state, like a chrysalis awaiting its transformation. Its large solar arrays remained folded, and its two sophisticated scientific instruments – the primary instrument, the Infrared Sounder, and the Copernicus Sentinel-4 mission's spectrometer – were switched off and secured. James Champion, MTG Project Manager at the European Space Agency (ESA), emphasized the complexity of this procedure. "Mating to the launch vehicle adapter is a critical step that requires exceptional precision. The operations involve using a crane to lower the satellite onto the adapter with millimeter accuracy, with the help of special guidance tools to ensure perfect alignment and mechanical connection," Champion explained. After the successful mating, detailed safety and functional checks followed to confirm that all connections were correctly established.

Finally, the assembly consisting of the satellite and its adapter was enveloped by the top of the rocket, known as the fairing. This cone-shaped structure is not just an aerodynamic element; it serves as a protective shield that guards the precious cargo from extreme pressure and heat during its passage through Earth's atmosphere. The entire encapsulated module was then carefully transported to a hangar at the launch pad and integrated with the rest of the powerful Falcon 9 rocket, waiting for the moment to begin its journey into space from Cape Canaveral.

High-Risk Operation: Fuelling

Approximately two weeks before the scheduled launch, one of the most dangerous phases of preparation took place – fuelling the satellite. Due to the extreme toxicity and flammability of the substances used, this activity requires the highest safety measures and is carried out only by a small team of top experts.

Two types of liquid fuel were loaded into the MTG-S1 satellite's tanks. The first was MON3, a red fuming liquid which is a mixture of dinitrogen tetroxide and nitrogen oxide, acting as a powerful oxidizer. This was followed by the loading of monomethylhydrazine (MMH), an extremely toxic, volatile, and flammable liquid. These two components form a hypergolic mixture, meaning they ignite spontaneously upon contact with each other, eliminating the need for an ignition system in space but posing a huge risk on Earth.

Due to the lethal nature of these chemicals, the operation is performed by technicians in special protective suits called SCAPE (Self-Contained Apparatus Protective Ensemble). These suits create a completely isolated and hermetically sealed environment, protecting the user from toxic fumes and direct contact with corrosive liquids. Only two specialists enter the fuelling room to handle the drums and carry out the procedure, while two colleagues monitor the situation from a safe control room, ready for emergency intervention. "Fuelling is an operation where we reduce the number of personnel involved to the absolute minimum," explained James Champion. "The propellant is extremely toxic, and there is a significant risk of spontaneous combustion or corrosion if it were to leak uncontrollably into the atmosphere."

A New Era of Earth Observation from Geostationary Orbit

With the ground preparations complete, MTG-S1 and its advanced instrumentation are ready for a 36,000-kilometer journey to geostationary orbit. From this position, the satellite will move at the same speed as the Earth rotates, allowing it to continuously monitor Europe and North Africa, providing data in a way that was not possible until now.

This mission carries two revolutionary instruments whose data will transform scientific and societal capabilities. The primary instrument of the MTG-S1 satellite, the Infrared Sounder, will do something extraordinary: every 30 minutes, it will create a detailed profile of temperature and humidity at different altitudes in the atmosphere over Europe. This ability to rapidly scan for atmospheric instability will allow meteorologists to predict the development of extreme weather events such as severe storms and hail much earlier and with greater accuracy.

The second key instrument on the satellite is the Copernicus Sentinel-4 mission's spectrometer. This instrument will measure the concentrations of key air pollutants every 60 minutes, including aerosols, ozone, nitrogen dioxide, and sulphur dioxide, with a level of detail and precision that will fundamentally change the way we forecast air quality across Europe. The data will enable better monitoring of industrial pollution, clouds of Saharan dust, or smoke from wildfires and issue timely warnings to citizens.

Both of these state-of-the-art missions, developed under the leadership of ESA in collaboration with numerous European partners, will address key scientific and societal challenges. The data they send will allow for better preparation for extreme weather events and more accurate warnings about air pollution that harms our health. Simonetta Cheli, Director of Earth Observation Programmes at ESA, expressed great satisfaction. "I am extremely grateful to the teams within ESA, in dozens of European companies, and at our partners who have contributed to the MTG-Sounder satellite and the Copernicus Sentinel-4 mission. These instruments will truly provide new and exciting ways to forecast and understand our atmosphere. I eagerly await the launch from Cape Canaveral and look forward to seeing how these missions will benefit society, enabling us to prepare for severe weather conditions and mitigate the risks of air pollution."

Source: European Space Agency