Interview — What satellites can tell us about Earth: Sentinels and Copernicus

What was going through your mind as Sentinel—2C took off?

It was incredibly emotional. What surprised me the most was how much it affected me. Standing there, everything was dark, and we couldn't even see the rocket's launch point from where we were.

Then, suddenly, a light appeared in the distance, cutting through the darkness, and we saw it rise. The sound was delayed, because the launchpad was so far away, which added to the anticipation. The moment the sound hit us, it was overwhelming.

The rocket carved this perfect semicircle into the sky and at one point, it disappeared into some low clouds, only to emerge again. It was so flawless that it almost felt unreal. I thought 'It is actually happening".

Usue Donezar

Expert - Copernicus Project Lead

ESA–S. Corvaja

I have worked with satellite imagery since my master's thesis in Wageningen in the early 2000s. I have always known about satellites — they are up there, collecting data — but the physical act of launching one into space was more of an abstract concept to me.

Seeing the rocket launch made it all real in a way that is difficult to describe. It is a simple thought, but it felt profound at that moment.

What are the improvements brought by Sentinel—2C?

Sentinel—2C provides continuity for Sentinel—2A. The European Union's Copernicus programme is vast and long-term maintenance needs to be an essential part of the plan. Sentinel—2C will ensure continuity in the data, bridging the time between Sentinel—2A, 2B, and eventually 2D. These satellites work in pairs, providing a solid foundation for our work at Copernicus Land Monitoring Service (CLMS).

Continuity is crucial for the kind of long-term monitoring we do at CLMS and the European Environment Agency (EEA). When you are dealing with environmental data, it is not always about increasing resolution or frequency, it is about building a consistent time series over many years. If you introduce changes too often, it becomes difficult to maintain consistency.

With Sentinel—2C, we will be able to have a reliable time series from the launch of Sentinel—2A all the way to the next generation of satellites—covering roughly 15 years. This consistent data stream is invaluable for tracking environmental changes over time.

Future generations of Sentinels will continue to bring improvements, such as better spatial resolution and other features.

What happens to older satellites?

Sentinel­­­—2A will eventually be retired. There were discussions about keeping three satellites in orbit simultaneously to increase the frequency of data collection, allowing us to capture images every three days instead of every five.

Countries like those in Scandinavia and Austria, where cloud cover on mountainous terrain make it challenging to get cloud-free observations, were the strongest advocates for this. Sentinel—2A has already outlived its expected seven-year lifespan. Although it is still functional, it is nearing the end of its mission, so the European Commission took the decision to not maintain it.

How does CLMS use the data from Sentinel—2?

CLMS is one of the largest users of Sentinel—2, as it is a satellite defined to monitor land and we are the service monitoring land within the Copernicus programme. This is why we have been involved in defining Sentinel—2’s specifications and why we are active in the definition of future missions.

Our service providers use the Sentinel—2 images to create various products, providing information related to land cover, land use, vegetation status, water resources, and even energy variables. For example, we can use machine learning to classify land cover automatically or to have products related to vegetation status. Alternatively, we can also use the data to carry out land use analyses, like distinguishing orchards from vineyards, which is often done manually.

How do these data impact the everyday lives of Europeans?

The data are useful even beyond policy and administration. For instance, farmers can use it to monitor the health of their crops, checking for water shortages, excess moisture,or the need for fertilizer. Timber industry can assess the status of forests without the need for on-site inspections.

We are also seeing a growing interest from insurance companies, which use our data to assess damage claims. Financial institutions are beginning to leverage the data for sustainability certifications and risk assessments.

There is huge potential for these data to be used in areas like civil protection, environmental compliance, and even preventing environmental crimes such as illegal logging or water extraction. One of Copernicus services has been tasked with monitoring environmental compliance, which includes tackling illegal activities like dumping or logging. While CLMS doesn’t produce specific products for this purpose, our data can certainly be used by others to identify such activities. It is a powerful tool for ensuring environmental laws are followed.

And I have to add that all these data are available and accessible online, and free of charge.

How can Copernicus land products be used at European level?

One of the advantages of our products is consistency. If you want to know the status of something across Europe, our products provide a consistent overview across the entire continent. This is crucial because, while national datasets are usually of higher quality for specific countries, we offer something that is harmonised across the whole area of interest. One of our flagship products, for instance, is the Corine Land Cover, which uses the same definition of land cover classes across all 39 member countries of the EEA and the UK. This consistency is a major benefit because you can compare land cover classes, for example, in Italy and Ireland, knowing they are classified using the same criteria.

This makes the Corine Land Cover one of the most widely used and most frequently downloaded products. The project dates back to 1990, and the next update was in 2000. Since then, it is been updated every six years, and we are currently working on the update for 2024.

How do you see the future of Sentinel data influencing environment and climate policy?

We are currently working on the definition of the third phase of the Copernicus programme, which will include new missions focused on areas like soil moisture and water quality. There is one mission I am especially excited about: hyperspectral imaging. This will allow us to monitor not only vegetation health but also soil composition in far greater detail. My master’s thesis was on hyperspectral data, so I am personally invested in seeing this technology evolve.

Looking ahead, we will continue adapting our portfolio to these new capabilities. With the next generation of Sentinels and the expansion missions, we will be able to improve the quality of the data we use and add entirely new monitoring capabilities. It is a very exciting time for Earth observation.

What would you like to highlight about Copernicus and the Sentinel programme?

The Copernicus programme has been transformative for Earth observation. When I started in this field, we had access to just one or two images, and now we can access a wealth of data for free. This has created a new paradigm in Earth observation, making it possible to operationalise what were once only theoretical concepts. It was revolutionary.

We should be incredibly proud of the fact that Europe led this initiative, inspiring other global actors, like NASA, to follow suit. The availability of open data has revolutionised how we monitor our planet and has had a tremendous impact on applied science.