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ESA's Sentinel programme watches the world to keep us safe

ESA's Sentinel programme watches the world to keep us safe
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The European Space Agency-developed satellite Sentinel-3A, recently launched from Plesetsk in Russia, has started its in-orbit Earth observation in order to provide a real- time picture of our planet’s health.

In future, on land, because of these onboard instruments, we can make forecasts and help forecast the harvests to come

The satellite is one of the many being launched to form the space component of the European Union’s Copernicus programme.

“The Sentinels are our guardians in space. It’s a satellite which observes our planet. Sentinel-3A, if you want, gives us a bigger picture. That means that instruments
onboard have a lower resolution, but scan the surface quicker because there’s less processing to do. This provides the everyday status of our planet,” says ESA’s Director of Earth Observation Volker Liebig.

The Sentinels will be useful to monitor changes in Earth’s climate and for more hands-on applications, such as marine pollution and biological productivity, to check vegetation health and measure the depth of ice, rivers and lakes.

“What we try to reach with the Sentinel satellites is what we have done years ago in meteorology. We built an operational satellite system to improve the forecast, and this is also what we had in mind with Copernicus, but this time for the environment and also for civil security,” continues Liebig.

Sentinel-3A carries four Earth-observing instruments with a series of cutting-edge sensors able to provide a whole range of new data with unprecedented coverage of the oceans.

“We can measure sea level rises here, but also current systems, like El Niño. We have another instrument which measures the ocean’s colour as we call it. We say that we can identify pollution, algae blooms
, but we can also see land cover changes on Earth: we have mega cities extending further, we have forest changes, agricultural area changes…
We also have an instrument to measure with millimeter accuracy the sea level rise,” says Liebig.

Over land, Sentinel-3A’s instruments will also provide unique information about surface vegetation, by measuring variables such as leaf area index, the fraction of absorbed photosynthetic active radiation and the terrestrial chlorophyll index.

“We want to make a contribution to food security as well,” insists Liebig. “In future, on land, because of these onboard instruments, we can make forecasts and help forecast the harvests to come.”

After checking that all the satellite elements are working well, the mission is expected to really begin operations in five months.

Sentinel-3A will provide global coverage every two days. Most of the data will be
processed systematically and available for users within a few hours.

“All data will be processed in real time. That means we can make it available after three hours to all users, not only across the Copernicus project, but also to a very powerful ground processing system. Data will be open and freely available to everybody,
you can download it via the internet,” promises Liebig.

This data will be a key factor also to measure, monitor and predict climate changes
over our planet in the coming decades, and is part of the Cop21 agreement, signed in Paris, on December 2015. Liebig is aware of his team’s responsibilities.

“We have auto-reporting duties in the context of the Cop climate treaty and this satellite data can help all nations to report. So every five years when this report has to be given, there is an input.”

There are two satellites for each Sentinel mission, A and B, flying in the same orbit.

Sentinel-3B is expected to join its twin Sentinel-3A by next year.