In the heart of the European Space Centre in Kourou, French Guiana, the final act of preparations for a launch that will define a new era of meteorology and climate monitoring is unfolding. Teams of experts, with a sense of pride and nostalgia, said goodbye to Europe's most advanced meteorological satellite, MetOp Second Generation-A1 (MetOp-SG-A1), as it was hermetically sealed within the protective fairing of the powerful Ariane 6 rocket. This crucial moment marks the end of physical work on the satellite and the beginning of the countdown to its journey into orbit, scheduled for August 13, 2025, at 02:37 Central European Time.

Since its arrival at the spaceport in mid-June, the MetOp-SG-A1 satellite has undergone a rigorous and meticulous preparation process. Every component, every system, and every instrument has been subjected to a series of detailed checks to ensure flawless functionality in the extreme conditions of space. One of the most demanding and dangerous tasks was fueling the satellite with nearly 800 kilograms of extremely volatile fuel, an operation that requires maximum precision and safety measures. Afterwards, the satellite was connected to the launch adapter, making it an integral part of the Ariane 6 rocket's payload.

The encapsulation within the rocket's fairing is always an emotional moment for the engineers and scientists who have worked on the project for years. It is the point of no return, after which the satellite remains hidden from view until the moment of separation in space. Marc Loiselet, head of the MetOp-SG project at the European Space Agency (ESA), shared the depth of this moment: "I have been working on this mission since 2012, and for the last two years, I have led the development and construction of this satellite, so this moment is particularly poignant. None of us will see the satellite again – the fairing will only open three minutes and 30 seconds after liftoff, as MetOp-SG hurtles towards its orbit around the Earth."

A new era for weather forecasting and climate studies

The MetOp Second Generation mission is not just a technological feat; it represents a quantum leap in our ability to observe and understand Earth's atmosphere. MetOp-SG-A1 is the first in a series of three pairs of satellites (type A and B) that will together ensure the continuous delivery of key meteorological data for more than twenty years. Its partner, MetOp-SG-B1, is scheduled to follow it into space as early as next year. This long-term program not only guarantees the continuation of vital global observations from polar orbit, crucial for accurate weather forecasting and climate change analysis, but also brings significant improvements. Compared to the first generation of MetOp satellites, the new series offers significantly higher accuracy and data resolution, as well as completely new measurement capabilities that will expand the scientific scope of the mission.

Each pair of MetOp-SG satellites consists of a type 'A' and a type 'B' satellite, which carry different but complementary instrument packages. In total, there are ten state-of-the-art instruments distributed across both satellites. Some are based on the proven technology of the previous generation, while others are completely new and represent the pinnacle of innovation in remote sensing.

Sophisticated technology at the heart of the MetOp-SG-A1 satellite

The type 'A' satellites, of which MetOp-SG-A1 is the first representative, are equipped with six revolutionary instruments. Among them are the next-generation Infrared Atmospheric Sounding Interferometer (IASI-NG) and the Microwave Sounder (MWS), which will together provide three-dimensional profiles of atmospheric temperature and humidity with unprecedented accuracy. There is also the METimage multispectral imager, which will create images of clouds and the Earth's surface in 20 spectral channels, enabling detailed analysis of the properties of clouds, aerosols, vegetation, and snow cover. Particularly innovative is the Multi-Angle, Multi-Channel, Multi-Polarisation Imager (3MI), which will provide unique data on aerosols in the atmosphere, key to understanding air quality and climate processes. In addition, the satellite carries a Radio Occultation (RO) sounder, which will also be on the type 'B' satellites, using signals from navigation satellites for precise measurements of temperature and humidity. The sixth and extremely important instrument is the Copernicus Sentinel-5 spectrometer.

Copernicus Sentinel-5: Guardian of our atmosphere

The Copernicus Sentinel-5 instrument, developed as part of Europe's flagship Earth observation program, represents the very pinnacle of technology for monitoring atmospheric composition. Building on the success of the Copernicus Sentinel-5 Precursor mission, this advanced imaging spectrometer will work in synergy with the other instruments on MetOp-SG-A1. Its primary task is the daily global mapping of key atmospheric pollutants such as nitrogen dioxide (NO₂), sulphur dioxide (SO₂), ozone (O₃), formaldehyde, carbon monoxide (CO), and methane (CH₄). This data is of crucial importance for monitoring air quality, assessing the impact of industrial activities and traffic on the environment, and protecting public health. Sentinel-5 will also provide vital data on stratospheric ozone, which protects us from harmful ultraviolet radiation, and on aerosols, tiny particles that affect climate and respiratory health.

Didier Martin, Sentinel-5 Project Manager at ESA, stressed the importance of this step: "The encapsulation in the rocket fairing, of course, also marks an important milestone for Sentinel-5. We too are saying goodbye to this new instrument, and our focus is now fully on next week's launch."

Final steps before the historic launch

After the satellite is safely housed inside the Ariane 6 rocket's fairing, the teams move into the remote monitoring phase. "From this point onwards, we are monitoring the satellite's environment within the protective fairing and carrying out checks to ensure we can configure and monitor the satellite on launch day. The pre-launch excitement is building day by day," added Nick Goody, ESA's Launch Campaign Manager for MetOp-SG-A1. Every parameter, from temperature to pressure inside the fairing, will be under constant surveillance to ensure the satellite reaches the launch pad in perfect condition.

European cooperation for a global goal

The MetOp Second Generation mission is the fruit of a long-standing and extremely successful collaboration between the European Space Agency (ESA) and the European Organisation for the Exploitation of Meteorological Satellites (Eumetsat). In this partnership, ESA is responsible for the design and construction of the satellites, ensuring they incorporate the most advanced technology available. On the other hand, Eumetsat is responsible for procuring launch services, developing the ground segment, operating the satellites in orbit, and, most importantly, for processing and distributing the data to the wide community of users worldwide. This data will be the backbone of the work of national meteorological services, research institutes, and environmental protection agencies for the next two decades. The Copernicus Sentinel-5 mission, as part of the broader program, is the result of close collaboration between ESA, the European Commission, Eumetsat, industry, service providers, and data end-users, demonstrating the power of a united Europe in addressing global challenges.