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Sentinel for sea level rise enters testing


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Stephane Corvaja / ESA


Flying under the Copernicus badge secures the future of the long-term program

The next satellite assigned to maintain "gold standard" measurements of sea level rise will enter final testing.

The Sentinel-6a will take from the long-running Jason spacecraft series when it was launched in November 2020.

These missions trace the height and shape of the Earth's oceans with a microwave altimeter.

Since 1992, orbiting instruments have observed an average sea level rise of 3.2 mm per year.

This trend is getting faster. The past five years, from 2014 to 2019, have witnessed an increase of 4.8 mm / year.

Sentinel-6a marks the first time this very important mission series will fly under the symbol of the EU Earth Copernicus Earth observation program.

This is still a joint venture between Europe (mainly France) and the US, but Copernicus' protection provides long-term financial security.

In the past, there was always some uncertainty about where funds would come to start the next iteration of spacecraft.

Now, not only Sentinel-6a is entering testing but the follow-up, Sentinel-6b, has all the money with construction that will begin in 2021.

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Changes in sea level will inform the estimated intensity of the storm

Space agency officials and industry officials gathered at the IAGB facility in Ottobrunn, near Munich, Germany, on Friday to celebrate a year to be launched.

The IABG company will inspect the Sentinel system to ensure they can fly into orbit using Falcon-9 rockets.

When it finally gets there, Sentinel-6a will spend several weeks walking with the current operational satellite, Jason-3.

This will allow scientists to cross-calibrate their "Poseidon altimeter".

This instrument is used to map various "hills" and "valleys" on the surface of the ocean below.

Understanding variations in altitude from time to time has many applications, both short and long term.

Just as air pressure tells meteorologists what is happening in the atmosphere, the height of the ocean will betray the details of the behavior of the water below the topmost layer.

Data provides clues to temperature and salinity. When combined with gravity information, it will also indicate the current direction and speed.

The oceans store a lot of heat from the Sun, and how they move that energy around the world and interact with the atmosphere is what drives the key elements of our weather and climate system.

A classic example is the El Nino phenomenon. It usually sees cold water in the east central Pacific overtaken every few years by waves of warm water from the west. This disrupts weather patterns around the world, bringing drought to some areas and heavy rain to other places.

Sentinel-6a will act as an early warning system for El Nino by detecting bumps that penetrate in warm surface waters.

The spacecraft will be managed every day by Eumetsat, an intergovernmental organization that operates European weather satellites.

It sends altimeter data to national institutions that meet to be digested in numerical models that produce weather forecasts.

The intensity of storms and the onset of heat waves, to give only two examples, will have clear signs of changes detected at sea level.

Eumetsat also manages another Copernicus mission equipped with an altimeter called Sentinel-3.

The characteristics of the instruments are very similar but the orbits that fly around the Earth are different.

Whereas Sentinel-6 moves between 66 degrees North and South, Sentinel-3 moves to 82 degrees.

"They are a system," said Eumetsat director general Alain Ratier.

"Altimeters are narrow plots and they are [look straight down] – but the oceans provide enormous variations throughout all time and space that we must fully sample. So for this you need several orbits, "he explained.

"Sentinel-6 has a 10-day return cycle but the distance between the rails is relatively large. This means it is optimized to monitor large features such as the Gulf Stream and Kuroshio Current. to see a small ocean vortex that might be 15-20 km away and move very slowly. "

The latest version of the Poseidon altimeter on Sentinel-6 comes with higher accuracy – such that scientists hope it can help reduce even some of the finer climate changes.

For example, there is hope that increasing levels of greenhouse gases in the atmosphere will cause the intensification of tropical trade winds. This should push warm equatorial surface waters to the west.

This is the kind of detail needed to make better predictions about the likely impact of regional sea level rise, said Benoit Meyssignac of the French Laboratory for Geophysical Studies and Spatial Oceanography.

"The response from this greenhouse gas – we see it in climate models and we start to see it in observations. However, because the uncertainty in observations is around 1.2-1.5mm / year regionally, we cannot relate it to confidence. But with Sentinel "We hope we will have the precision and accuracy needed," he told BBC News.

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Artwork: Sentinel-6 will be launched with Falcon-9 rockets in November 2020

The European-US partnership at the space agency level has become very important in recent years.

Sentinel-2 is a land lover whose data products overlap with the American Landsat Earth observation program – deliberately made so; each imaging instrument is built to complement each other.

This work of the Sandra Cauffmann team, acting director of the Earth Sciences Division at NASA, wants to strengthen.

"We are talking with the European Space Agency (Esa) and we will hold a workshop in February to consider potential future partnerships in Landsat architecture. It makes sense that Sentinel-2 and Landsat are advancing together," he said. the word.

As well as the European Commission, Esa, NASA and Eumetsat – the main partners on the Sentinel-6 project including the French space agency (Cnes), the US National Oceanic and Atmospheric Administration (NOAA) and Airbus, which build satellites.

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