OHB Sweden is building Europe’s Sterna meteorological constellation: 20 satellites for more precise forecasts from the Arctic to the Mediterranean
The European Space Agency has awarded the Swedish company OHB Sweden a contract to develop and build 20 small satellites for the EPS-Sterna programme, a new European meteorological constellation that is expected to provide significantly more frequent measurements of atmospheric temperature, humidity and clouds from 2029 onwards. This is one of the most important European projects in the field of operational meteorology in recent years, because the system is expected to improve very short-range forecasts and so-called nowcasting, especially in areas where the weather changes rapidly and where there are observational gaps, such as the Arctic, the North Atlantic and the Mediterranean. The agreement was signed on 18 March 2026, and according to OHB Group data the contract is worth 248 million euros. Politically and economically, this is an important signal that Europe wants to strengthen its own independence in space-based Earth observation and reduce reliance on data from outside the European system.
From prototype to operational constellation
The new project builds directly on the success of the Arctic Weather Satellite, an experimental satellite that ESA launched on 16 August 2024 from Vandenberg in California. That satellite was developed as proof that even a smaller, cheaper platform can carry a sophisticated microwave instrument capable of useful meteorological measurements. As early as the beginning of 2026, ESA announced that this very demonstrator had fulfilled its key task: it showed that a constellation of similar satellites can provide far more frequent observations than classic polar meteorological satellites, which most often pass over a given location only twice a day. In practice, this means that meteorological services can identify the development of storms, incursions of cold air, changes in water vapour content and other processes that directly affect forecast quality earlier in critical situations.
That is precisely why EUMETSAT, the European organisation responsible for operational meteorological satellites, gave the green light to the EPS-Sterna programme. The EUMETSAT Council unanimously approved the start of the programme in January, and the organisation said that the system would enable microwave measurements of temperature, humidity and clouds with “an unprecedented frequency”. EUMETSAT also estimates that the total economic benefit of the programme during its lifetime could reach at least 30 billion euros, with a benefit-to-cost ratio of up to 51 to 1. Such estimates do not mean only a better scientific picture of the atmosphere, but also concrete benefits for transport, energy, agriculture, civil protection and planning responses to extreme weather events.
Why the Arctic is at the centre of the project
Although Sterna will serve the whole world, the Arctic remains the main strategic reason why the project is being accelerated. In its explanations, ESA states that the Arctic is the fastest-warming region on Earth and an important source of processes that affect the weather over Europe. In such an environment, the amount of water vapour can change quickly and strongly, and these data are among the key factors for the accuracy of numerical models. The problem is that the classic observation network in the far north is not dense enough, and geostationary satellites, due to their position above the equator, do not have good visibility there. Polar satellites cover that area, but not frequently enough to provide an almost continuous insight into rapidly changing conditions.
The new constellation is therefore conceived as a response to a very specific operational problem. Instead of relying on one large satellite, Europe is introducing a group of smaller satellites that together create a dense network of passes over the same areas. According to ESA and EUMETSAT, most data should be available within approximately one hour, while full global coverage would be achieved in about three hours. Compared with current polar systems, this is a significant leap, especially for predicting sudden changes that can develop into dangerous weather episodes.
What exactly OHB Sweden will build
According to official announcements from ESA and OHB Sweden, the constellation will consist of six satellites in orbit at any given time. However, the programme is not designed as a one-off delivery of just those spacecraft. During the operational lifetime of the system, the satellites will be renewed two more times in order to ensure uninterrupted data delivery at least until 2042. This means that a total of 18 operational satellites will be built, along with two additional backup units, that is, a total of 20 spacecraft that are the subject of the current contract. The first six satellites are expected to be launched in 2029, which leaves a very short development schedule for a project of this size.
That is precisely why ESA and its industrial partners are once again emphasising the so-called New Space approach. This development model implies a faster design cycle, stronger reliance on already proven technology, lower satellite mass and stricter cost control than in traditional large Earth observation programmes. ESA recalled that the Arctic Weather Satellite was also developed in just 36 months, and with a much tighter budget than is usual for classic missions. For the European space industry, Sterna is therefore both a technological and manufacturing test: it must show that the continent can industrialise an entire series of meteorological microsatellites within a relatively short period without any drop in data quality.
The microwave radiometer as the heart of the mission
Each satellite in the constellation will carry a cross-track scanning microwave radiometer, an instrument intended to measure profiles of atmospheric humidity and temperature. Such measurements are particularly valuable because they enable observations through clouds as well, which optical sensors cannot do in the same way. That is why microwave data are of great value for operational meteorology, because they provide information about the state of the atmosphere in situations when the weather is most unstable and when forecasts are most sensitive to the quality of input data.
The additional importance of this project stems from the fact that the Arctic Weather Satellite has already shown that a small platform can deliver data of sufficient quality for real use in forecasting centres. The European Centre for Medium-Range Weather Forecasts, ECMWF, announced that it began operationally assimilating data from that satellite on 10 July 2025. ECMWF states that the new observations brought a robust improvement in forecasting and that they complement data from similar, but much larger, satellite systems operated by EUMETSAT, the American NOAA and the Chinese meteorological administration. This is one of the strongest arguments in favour of continuing the programme, because this is no longer merely the promise of a prototype, but data that have already entered the operational chain of European weather forecasting.
Broader benefit: the Mediterranean, extremes and safety
Although the previous demonstrator has the Arctic in its name, Sterna’s impact does not end in the far north. ESA explicitly points out that the higher measurement frequency should improve the monitoring of rapidly developing weather systems and the forecasting of dangerous phenomena in vulnerable regions, among which the Mediterranean is specifically mentioned. This is also important for southern Europe, including Croatia, because it is over the Mediterranean that cyclones, intense precipitation episodes, storm systems and heat intrusions form and intensify, and these can have serious consequences for the coast, transport, the power system, tourism and civil protection.
In operational terms, denser and faster measurements from space mean a more reliable initial state of the models. And the initial state is precisely what determines whether a model will correctly estimate where a storm will develop, how much moisture the air will contain before extreme precipitation, or how quickly a frontal disturbance will intensify. When meteorological services receive better-quality data earlier, they also gain a better chance of issuing timely warnings. At a time when Europe is recording a series of heatwaves, heavy rains, floods, droughts and fires, investment in satellite infrastructure is therefore simultaneously a scientific and a safety decision.
The European cooperation model of ESA and EUMETSAT
After signing the contract with OHB Sweden, ESA will lead the procurement of the satellites according to the already established cooperation model with EUMETSAT. This model is already being applied to other key European meteorological missions, primarily the geostationary Meteosat satellites and the polar MetOp satellites. The division of roles is clear: ESA leads the development and procurement of the space segment, while EUMETSAT ensures the operational use of the system and the integration of the data into the daily work of European meteorological services.
Such an allocation of responsibilities also carries political weight for Europe. At a time of intensified discussions about strategic autonomy, infrastructure resilience and security of data supply, meteorological satellites are no longer only a technical issue. They are part of the broader infrastructure on which warnings for the population, decisions on aviation and navigation, flood risk assessments, energy system management and planning responses to climate extremes depend. EPS-Sterna thus enters the group of programmes that simultaneously carry scientific, industrial and geopolitical significance.
Swedish industry receives its largest satellite contract to date
For OHB Sweden and the Swedish space sector, this job represents an exceptional industrial leap. The company announced that this is the largest satellite contract in Sweden’s history. National partners are also involved in the project, including AAC Omnisys, a subsidiary of AAC Clyde Space, which supplies the mission’s meteorological payload, namely the microwave radiometer developed in Gothenburg. This means that the project is not limited only to satellite construction, but also to the long-term anchoring of technological competences, production and highly educated jobs in the Swedish and European space supply chain.
OHB Sweden’s management said that the contract represents an extraordinary milestone both for the company and for the entire Swedish space community. They emphasised that they had already demonstrated the functionality of the system and the quality of the data on its predecessor, the Arctic Weather Satellite, and that EPS-Sterna confirms the readiness of the company and its partners to lead, industrialise and deliver critical space infrastructure for Europe. Behind these statements lies a broader European interest as well: to prove that the production of smaller but high-performance satellites can become a sustainable pillar of European industrial competitiveness.
Why this is more than just another space project
At first glance, this is another contract between a European agency and industry. But viewed more broadly, Sterna shows how the logic of meteorological observations from space is changing. Classic models relied on a large number of functions combined on a relatively small number of large and expensive platforms. The new approach, as demonstrated by EPS-Sterna, moves towards distributed systems, faster data refresh and more flexible fleet renewal. This also reduces the risk that the entire system will lose a key function because of a failure on a single spacecraft, while at the same time providing better temporal resolution of observations.
Sterna is also an indicator of how the boundary between an experimental mission and operational use is increasingly shifting. The Arctic Weather Satellite did not remain only a technology demonstrator, but entered operational data assimilation at ECMWF. This opened the way for the political decision on a full constellation to be made more quickly and with less uncertainty than is usual in large public projects. In addition, the programme is arriving at a time when climate change is increasing weather volatility, while the public and institutions expect more precise and earlier warnings of dangerous phenomena. For that reason, the decision to build 20 satellites for EPS-Sterna is not only an investment in space technology, but also an investment in a more resilient European meteorology, the safety of the population and Europe’s long-term ability to monitor changes in the atmosphere with its own means.
Sources:- ESA – Arctic Weather Satellite – official mission page with the launch date, basic technical data and instrument description.- ESA – Arctic Weather Satellite paves way for constellation – official announcement on the demonstrator’s role in launching the EPS-Sterna programme, the structure of the constellation and the expected benefits.- EUMETSAT – Europe backs transformative polar satellite constellation – decision of the EUMETSAT Council, the programme’s operational plan, estimate of economic benefit and timeline.- EUMETSAT – EPS-Sterna – description of the programme, the initial constellation and the system’s operational purpose.- ECMWF – Small-but-mighty Arctic Weather Satellite now assimilated at ECMWF – confirmation of operational data assimilation from 10 July 2025 and assessment of the impact on forecasts.- OHB Sweden – OHB Sweden Signs EPS-Sterna Satellite Constellation Contract – announcement of the contract signing on 18 March 2026 and the project’s industrial significance for Sweden.- OHB SE – Newsroom – announcement of the contract value of 248 million euros and the project’s positioning within the group.
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