The European Union has launched its latest Sentinel Earth observation spacecraft.
Sentinel-3b is a multipurpose satellite, but will concentrate much of its work on the oceans, monitoring its behavior and health.
The spacecraft climbed a converted intercontinental ballistic missile from Russia's Plesetsk cosmodrome.
It will join an identical platform, Sentinel-3a, which was sent to orbit two years ago.
This is now the seventh satellite the EU has launched in its ambitious Copernicus program, which seeks to place the largest volume of Earth observation data ever acquired in the hands of politicians, scientists, businesses and the general public.
All that the Sentinels observe is open information that anyone in the world can access with a computer and an Internet connection.
Missions 3a and 3b were designed to perform a wide variety of functions, from measuring the thickness of Arctic sea ice and monitoring forest fires, to helping with hurricane forecasting and identifying marine pollution.
As with all Sentinels, the acquisition and early operation of 3b falls on the European Space Agency (Esa), the EU technical agency for Copernicus. But for this new mission, Esa has decided to do something a little different.
He has made the Russian Rokot launcher inject 3b just ahead of 3a so that the performance of the couple's instruments can be compared directly by flying over the same portion of the Earth.
"3b will fly 210 km ahead of 3a, 30 seconds in time, and that will allow them to acquire data on more or less the same dirt track," explained Esa's mission scientist, Dr. Craig Donlon . "We will do this for 4.5 months and then we will re-derive 3b to an orbit of 140 degrees, 50 minutes apart," he told BBC News.
This should eventually see two perfectly calibrated spacecraft that make neatly interspersed observations of the planet. The production of the series Sentinel-3 is led industrially by France, by Thales Alenia Space, but benefits from the contributions of more or less 100 companies across Europe, including the United Kingdom.
Great Britain has had the primary responsibility to test the Sea Surface and Soil Temperature Radiometers (SLSTR) on each spacecraft.
The participation of the United Kingdom after Brexit in the flagship space programs of the EU is currently the subject of much uncertainty, and future cooperation in the Galileo satellite navigation system seems increasingly unlikely. But there is hope that the evils of Galileo are not reflected by Copernicus.
Britain once again insisted on its desire to remain on the Earth observation program on Wednesday. And to emphasize this intention, the United Kingdom Space Agency trumpeted the new feasibility studies of ES granted to Great Britain to plan future Sentinels that would be launched in the 2020s, some years after the nation formally left the EU.
Sam Gyimah, Minister of Science, said: "The space sector in the United Kingdom is a success story and our capabilities in satellite Earth observation technology are second to none." These last contracts confirm the vital role of research, innovation and British industry in Copernicus.
"We have been clear that we want our companies and universities to continue to participate in key EU space programs, as long as they can participate in a fair and open manner. Our main role in the European Space Agency will not change when we leave the EU, and this government will ensure that the United Kingdom thrives in the commercial space age through our modern industrial strategy. "
The Sentinel series financed with European funds  Sentinel -1: Radar satellite that can see the surface of the Earth in all climates
Q What is the Copernicus program?
- EU project that is being obtained with the help of the European Space Agency
- Gather the whole Earth – data monitoring, from space and soil  Will use a variety of spacecraft, some already up , others will fly
- They are expected to be of great value to scientists studying climate change
- Important for disaster response: earthquakes, floods, fires, etc.
- The data will also help design and enforce EU policies: fishing quotas, etc.