The launch took place at Vandenberg Base in the western United States at 3:20 pm on Tuesday (11:20 pm Tuesday in Lisbon), aboard a SpaceX Falcon 9 rocket.

"We have begun our flight," the European Space Agency immediately indicated on its 'site'.

The 2.2-tonne satellite designed by Airbus will operate 400 kilometres above the Earth and should revolutionise the understanding of the effects of clouds on the climate, which can cause the Earth to cool or warm, ESA highlighted.

"Tonight's lift-off is a reminder that space is not just about exploring distant galaxies and planets, but also about understanding our beautiful and fragile home," stressed Josef Aschbacher, ESA's director, in a video posted on social media on Tuesday.

Clouds are complex objects that act differently on the climate, depending on their altitude in the troposphere, the lowest layer of the atmosphere.

These "are one of the main contributors to climate change and it is one of the ones we know the least about," Dominique Gilliéron, head of ESA's Earth observation projects department, explained to the France-Presse (AFP) agency.

Some, such as cumulus clouds, formed by water vapour and located at low altitude, act as a 'parasol': being very white and very bright, they reflect the Sun's radiation back into space - an effect called albedo - and cool the atmosphere.

Others, such as high-altitude cirrus clouds, made of ice, on the other hand, allow solar radiation to pass through, which heats the Earth. The planet re-emits thermal radiation that "the cirrus clouds will capture, which keeps the heat in," Dominique Gilliéron explained during a press conference.

These data demonstrate the importance of assessing the nature of clouds according to altitude, dissecting their vertical structure, which no satellite has done so far, stressed Simonetta Cheli, director of Earth observation programmes at ESA.

ESA's pioneering mission, in collaboration with the Japanese agency Jaxa, will also analyse aerosols, tiny suspended particles (such as dust, pollen or human pollutants such as combustion ash), on which water condenses and are the precursors of clouds.

EarthCARE is also equipped with a multispectral imager, which will provide information on the shape of clouds, and a radiometer to probe their temperature.

The European mission, planned for three years, replaces NASA's CloudSat and CALIPSO satellites, whose missions are now complete.

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