On the night of December 16 to 17, 2025, the European satellite navigation system Galileo enters a new phase of development: an Ariane 6 rocket will launch from Europe's Spaceport in Kourou, French Guiana, carrying two new satellites designated as SAT 33 and SAT 34. This is the 14th operational launch in the Galileo program (L14), but also a historical milestone, as it marks the first time satellites of this constellation will head into orbit aboard the new heavy-lift Ariane 6 rocket. The scheduled liftoff time is December 17 at 6:01 Central European Time, corresponding to 5:01 Coordinated Universal Time (UTC), targeting a Medium Earth Orbit at an altitude of approximately 22,922 kilometers.

The two new satellites will upgrade the existing first generation of the constellation and increase the precision, availability, and robustness of the signals used today by billions of people worldwide via smartphones, car navigation systems, aircraft, ships, and critical infrastructure. After separating from the rocket about three hours and 55 minutes after liftoff, SAT 33 and SAT 34 will gradually raise themselves to their operational orbit at about 23,222 kilometers, where they will join the other satellites in the so-called Medium Earth Orbit (MEO) and begin delivering data for positioning, navigation, and timing.

Behind this launch stands a complex chain of European institutions and industrial partners. The European Space Agency (ESA) is responsible for the launch service contract with Arianespace, which operates the Ariane 6 rocket. The satellites were manufactured by the German company OHB in Bremen, as part of ESA's program to build the first generation of Galileo, while after their arrival in orbit, their commissioning and daily supervision will be taken over by the EU Agency for the Space Programme (EUSPA) based in Prague. The European Commission, as the political sponsor of the program, uses Galileo to strengthen the strategic autonomy of the European Union in the field of satellite navigation and precise timekeeping.

From the warehouse in Bremen to the equator: the journey of SAT 33 and SAT 34

The story of this launch does not begin on the ramp in Kourou itself, but in an industrial hall in Bremen, where SAT 33 and SAT 34 were stored after the completion of production and integration. On November 4, 2025, the satellites left the OHB factory and headed by truck towards Luxembourg. This segment of the journey, although seemingly routine, is strictly choreographed: special transport containers maintain controlled temperature and humidity, dampen vibrations, and protect sensitive electronics and optics from shocks and dust.

In Luxembourg, the convoy arrived at the airport, where the satellites were loaded onto a cargo aircraft designed for transporting sensitive space cargo. A flight across the Atlantic followed, lasting just over nine and a half hours to French Guiana, a French overseas department on the northern coast of South America. The choice of Kourou as Europe's spaceport is not accidental: the proximity to the equator provides an additional "free boost" thanks to Earth's rotation, so the rocket can carry a heavier payload or use less fuel for the same orbital target.

After landing in French Guiana on November 6, 2025, the satellites were carefully unloaded from the aircraft. Under controlled conditions and with constant supervision by expert teams, the containers with the cargo were transferred to special trucks that drove them to the premises of Europe's Spaceport. In Kourou, one of the most complex industrial complexes in the world, the satellites are placed in clean rooms where every step is carried out according to a detailed launch campaign plan.

Fit check and functional tests: checking every screw and bit

Between November 8 and 19, teams from ESA, industrial partners, and Arianespace conducted a key phase of checking the compatibility of the satellites and the rocket – the so-called fit check. In this phase, the satellites are temporarily connected to the adapter that will hold them at the top of the rocket during flight. Mechanical interfaces, dimensional accuracy, the position and strength of connection points are checked, as well as all electrical connections that will enable power supply, communication, and functional tests during preparations.

The fit check is a combination of precision engineering and complex logistics. Even minimal deviations in alignment can cause unwanted stresses during launch, when vibrations, acoustic shocks, and aerodynamic forces reach their peak. Therefore, every screw, support, and connection is checked multiple times, using laser measurement systems and computer models that simulate flight conditions. Only when all parameters meet the prescribed limits is the adapter officially approved for integration with the rocket.

In parallel with this, engineers conduct functional tests of the satellites. This is a detailed "health check" of all subsystems: power supply, communication systems, navigation antennas, the satellite platform, as well as the precise atomic clocks that represent the heart of the navigation mission. The software that controls the satellites is also tested, including the final versions of the flight software that will be active in orbit. Every anomaly or suspicion is recorded, analyzed, and if necessary rectified before proceeding to the next phase of the campaign.

When it is confirmed that all subsystems are working in accordance with specifications, the satellites are switched off and prepared for the fueling phase. From that moment until arrival in orbit, they remain "silent" – they are no longer switched on, in order to reduce the risk of any unplanned changes to the configuration or software.

Dangerous but necessary: hydrazine fueling and SCAPE suits

The next step in launch preparation is filling the satellites with propellant, most often hydrazine. It is an extremely toxic and flammable substance that requires strict safety protocols. Because of this, fueling is performed in a separate facility of the spaceport, separated from the main integration halls. Before transport to that facility, the satellites are repacked into their transport containers to be protected from vibrations, temperature changes, and humidity during the short drive.

Before the fueling itself, the satellites undergo detailed pressure testing of the propulsion system. Leaks on valves, tanks, and pipes are checked under conditions that simulate actual operating pressure. Only when measurement instruments confirm that the system is completely leak-proof do experts give the green light to start fueling.

Working with hydrazine is entrusted to a small group of highly specialized experts working in SCAPE suits (Self-Contained Atmospheric Protection Ensemble). These suits look like space suits but are adapted for work in a contaminated environment: they have their own air supply system, multi-layer protection against chemicals, and limit the operators' contact with the surroundings. During fueling, the number of people in the clean room is reduced to a minimum, while the rest of the team monitors the procedure via cameras and sensors from the control room.

Hydrazine is crucial for satellite operation in orbit: the fuel is used for minor orbit corrections, maintaining the correct position in the constellation, and managing satellite orientation. In Medium Earth Orbit, at an altitude of about 23,222 kilometers, even small changes in speed and position have a significant effect on the geometry of the constellation, so precise and economical use of fuel is of great importance for the long lifespan of the satellites.

Ariane 6: the new backbone of Europe's access to space

Ariane 6 is the new generation of European heavy-lift rocket, designed to ensure the European Union and its partners long-term and competitive autonomy in access to space. Compared to the previous Ariane 5, the new rocket is more modular and flexible: it can fly in configurations with two or four auxiliary boosters, allowing it to adapt to different types of missions – from launching satellites into low Earth orbit, through launching into geostationary orbit, all the way to interplanetary missions.

For the Galileo L14 launch, the Ariane 62 configuration was chosen, with two P120C solid-fuel boosters. Together with the rocket core, in which the Vulcain 2.1 engine runs on liquid oxygen and hydrogen, they ensure powerful thrust in the first phase of flight. After they consume their fuel, the boosters separate and fall into a pre-defined area of the ocean, while the core continues to work until the moment of separation, after which the upper stage ignites.

The upper stage of Ariane 6 is powered by the Vinci engine, also on cryogenic fuel (liquid oxygen and hydrogen), but with the capability of multiple ignitions. It is precisely this capability that makes the rocket particularly suitable for missions like Galileo, where it is necessary to precisely shape the orbit in multiple phases. Two ignitions of the upper stage are planned for this mission: the first to lift the payload into the target Medium Earth Orbit, and the second to fine-tune the orbit parameters before satellite separation.

After SAT 33 and SAT 34 leave the adapter and begin independent flight, the upper stage of Ariane 6 will not remain near the operational orbits. According to European standards for space debris mitigation, it will transfer to a so-called "graveyard" orbit, sufficiently distant from active satellites to reduce the risk of collisions and long-term creation of debris in Medium Earth Orbit.

What SAT 33 and SAT 34 will do in the Galileo constellation

Galileo is the first global satellite navigation system under civilian ownership, designed from the start as a civilian infrastructure of the European Union. Currently, it disposes of dozens of operational satellites in three orbital planes, and the new two satellites SAT 33 and SAT 34 will add additional reserves and flexibility to the constellation. Although they belong to the first generation, they are constructed so that they can seamlessly fit into the existing system architecture and work side by side with future second-generation satellites.

Each Galileo satellite carries highly precise atomic clocks that generate reference time with an error of just a few billionths of a second. By combining signals from multiple satellites, receivers on Earth – from smartphones to professional equipment in aviation and maritime sectors – can calculate their position with a margin of error of just a few meters, and even better in special services. Galileo also offers encrypted signals for public services and security agencies, thereby enabling more robust navigation in crisis situations.

Adding new satellites is particularly important for ensuring the so-called availability and continuity of service. If a satellite must be temporarily switched off for any reason or its projected lifespan expires, a new spacecraft can take over its role, and users on Earth will not notice an interruption in service. Satellites like SAT 33 and SAT 34 thus act as insurance for the entire system, enabling planned technical interventions and a gradual transition towards the future second generation of Galileo.

Galileo in smartphones, industry, and emergency services

Although Galileo is often mentioned in the context of rockets and space, its key role is on Earth. The system's navigation signals are already integrated into the vast majority of modern smartphones, car navigation devices, and professional logistics systems. Thanks to the combination of signals from multiple global systems (GPS, Galileo, BeiDou, GLONASS), end users get faster positioning, better coverage in urban canyons, and more precise route determination.

In transport, Galileo supports the development of smart mobility, from road traffic management systems to railway applications that require reliable information on train positions. In air traffic, it is used for approach and landing procedures, and in maritime transport, it helps ships move through narrow waterways and ports. In agriculture, it enables precision sowing and fertilization, i.e., optimization of resources in fields. It is also crucial for energy, banking, and telecommunications, because applications that depend on time synchronization use exactly satellite systems to obtain reference time.

One of the lesser-known but extremely important elements of Galileo is the Search and Rescue (SAR) service. Satellites receive signals from transmitters in life jackets, aircraft, or ships in distress and forward them to centers on Earth, shortening the time needed to locate a person in need of help. Newer satellites, including those of the first generation, also support a return message to the user, confirming that the distress call has been received and forwarded to the competent services.

Europe's strategic autonomy and the future of Galileo

By developing Galileo, the European Union ensures that a key service of global navigation and precise time does not depend exclusively on systems under military or foreign control. Although Galileo cooperates and is interoperable with other global satellite navigation systems, the fact that it is under the civilian ownership of the Union gives European institutions and member states greater security regarding the long-term availability of the service, especially in crises and geopolitical tensions.

The launch of SAT 33 and SAT 34 is also part of a broader system modernization strategy. After the completion of the deployment of the remaining first-generation satellites, the launch of the second generation of Galileo is foreseen, with improved instruments, stronger signals, and greater resistance to jamming. Contracts have already been signed for the launch of the first pair of second-generation satellites on Ariane 6, confirming that the new rocket will be the long-term backbone of European navigation missions.

Ariane 6, with its modular approach and ability to adapt to different payloads, is a key element of the European Union's so-called "space ecosystem". In combination with Galileo, the Copernicus Earth observation program, and future space infrastructures, Europe strives to create an integrated system of services from orbit: from precise positioning and timing, through climate monitoring, to security and defense applications.

Launch campaign under the magnifying glass of the expert and general public

As December 17, 2025 approaches, the Galileo L14 launch campaign is being followed under the watchful eye of experts, industry, and the general public. Every step – from final checks on the satellites, through integration onto the top of Ariane 6, to the final countdown in the control room – is planned weeks in advance. Special attention is paid to weather conditions over Kourou, since strong winds at high altitudes or electrical activity in the atmosphere can lead to a postponement of liftoff.

European institutions and industrial partners also use the launch as an opportunity to further inform the public about the importance of space infrastructure. Through live broadcasts, educational materials, and multimedia content, it is explained how navigation signals are created in orbit, how they reach receivers on Earth, and in what ways they are used in everyday life. Thus, a technically complex event is brought closer to citizens, while simultaneously encouraging the interest of young people in STEM fields and space technologies.

The launch of SAT 33 and SAT 34 on Ariane 6 is therefore not just another technical task in line, but also a strong message about the technological maturity of the European space industry. A successful mission will further consolidate Galileo's position as one of the most precise satellite navigation systems in the world and confirm Ariane 6 as a reliable and flexible rocket for a range of future European and international missions.