Although it was initially conceived only as a technology demonstrator for a future satellite constellation, the European Space Agency's (ESA) small Arctic Weather Satellite has already achieved success that surpasses all expectations. The European Centre for Medium-Range Weather Forecasts (ECMWF), one of the world's leading institutions in this field, has begun to operationally use its data in its systems for creating forecast models. This step represents an exceptionally strong confirmation of the mission's quality and value, proving that even smaller, agilely developed satellites can bring revolutionary advances in science and everyday life.

This mission, which was realized from concept to launch in a record time of just three years and with a significantly smaller budget compared to traditional space projects, delivers exceptionally valuable data on atmospheric humidity and temperature. The data collected from this compact satellite is now being integrated with numerous other observations from various sources. It is combined with short-term forecasts based on earlier measurements to create the most accurate possible picture of the current state of the Earth's atmosphere. This detailed analysis serves as a key starting point for generating all future weather forecasts, from short-term to long-term.

A revolution in meteorological data collection

The information provided by the microwave radiometer on the Arctic Weather Satellite complements data from similar, but much larger and more expensive satellites operated by organizations such as the European Organisation for the Exploitation of Meteorological Satellites (Eumetsat), the U.S. National Oceanic and Atmospheric Administration (NOAA), and the China Meteorological Administration (CMA). The key advantage of this satellite lies in its agility and specialized sensors that open up new possibilities in Earth observation.

For the first time, the Arctic Weather Satellite is operating in the so-called "sub-millimetre" spectral band, using wavelengths shorter than one millimetre. This technology provides scientists with a completely new insight into the formation and structure of ice clouds, which has been extremely difficult to track with existing instruments until now. The mission has thus unequivocally proven that high-quality, passive microwave measurements can be obtained using a small and cost-effective satellite. Launched about a year and a half ago, this prototype, developed for a fraction of the cost of a traditional Earth observation mission, has already shown that the "New Space" approach – which involves rapid development at lower costs – can be successfully applied to a future constellation of similar satellites.

The decision by ECMWF to assimilate its data into its operational forecasting system is the strongest possible recognition of this mission's excellence. Analyses have shown that the data from this satellite brings a robust improvement in forecasts, especially when it comes to wind prediction. On forecast maps, the areas with improvements are clearly visible. In addition, the new 325 GHz channel used by the satellite allows for the detection of lower radiation temperatures, providing a much clearer depiction and analysis of powerful cyclones like typhoons, enabling more precise tracking of their development and path.

The "New Space" philosophy as the key to success

Ville Kangas, the Arctic Weather Satellite project manager at ESA, expressed immense pride in the mission's achievements. "Although we were confident that our 'New Space' approach to developing and building the satellite would succeed, its performance in orbit has far exceeded our expectations," he stated. "Given that this is just a demonstrator – a precursor to a potential constellation of satellites capable of delivering a near-continuous stream of data for very short-range weather forecasting in the Arctic and beyond – we couldn't be more pleased with what has been achieved."

With a mass of just 125 kg and dimensions of 1.0 m × 5.3 m × 0.9 m, the Arctic Weather Satellite falls into the category of small satellites. Its key instrument is a 19-channel cross-track scanning microwave radiometer that provides high-resolution vertical profiles of atmospheric temperature and humidity in all weather conditions, regardless of cloud cover. Despite its name, the satellite collects measurements worldwide. However, its humidity data is particularly valuable for weather forecasting in the Arctic region, where water vapor concentrations can change extremely rapidly and dramatically, having a significant impact on weather patterns across the entire Northern Hemisphere.

The Arctic in focus: The global significance of the polar region

The consequences of the climate crisis are felt much more strongly in the Arctic than in other parts of the world, a phenomenon known as "Arctic amplification." However, what happens in the Arctic does not stay in the Arctic; these changes affect the Earth system as a whole, altering ocean currents and global weather patterns. Information from the Arctic Weather Satellite and a potential future constellation, named EPS-Sterna, will provide invaluable support for climate change research and a better understanding of these complex processes.

The proposed EPS-Sterna constellation would consist of six satellites, ensuring much greater temporal coverage and faster data refresh rates. It is planned that each satellite in the constellation will be replaced three times during its operational life to ensure a continuous delivery of data for many years. It is envisioned that ESA would build the EPS-Sterna constellation in collaboration with Eumetsat, following the established and proven successful model used for other European meteorological missions, such as the geostationary Meteosat satellites and the polar-orbiting MetOp satellites.

Existing systems have their limitations. The geostationary Meteosat satellites, located at an altitude of 36,000 km above the equator, send images every 15 minutes but have no visibility at higher latitudes near the poles, making them unsuitable for Arctic weather forecasting. On the other hand, the MetOp satellites provide data over the poles as they orbit the Earth at a lower altitude, but it can take up to 24 hours to achieve global coverage. The EPS-Sterna constellation of six satellites would fill this critical gap in temporal coverage, enabling so-called "nowcasting" – monitoring and forecasting weather in the very short term. If the EPS-Sterna constellation becomes a reality, it would complement existing missions such as MetOp Second Generation, the US JPSS system, and the Chinese Fengyun polar meteorological missions, doubling the number of orbital planes from three to six and thus dramatically improving the global observing system.