A UK-assembled satellite is set to go into orbit shortly to monitor air quality around the globe.
Its Dutch-designed instrument will induce daily maps of polluting gases and particles known to be harmful to health.
S5P will ride to orbit on a converted Russian intercontinental ballistic missile called a Rockot.
Lift-off from the Plesetsk Cosmodrome is scheduled for 12:27 local period( 10:27 BST; 09:27 GMT ).
Controllers will know they have a functioning satellite in position above countries around the world about an hour-and-a-half afterward when they first receive a radio communication from S5P.
Europe schemes Sentinel spacecraft expansion UK wants to stay in EU spacecraft project Mission tracks global pollutant trends Image caption Image caption EU project that is being find with European Space Agency assistance Pulls together all Earth-monitoring data, from space and the ground Will use a range of spacecraft – some already up there, others yet to fly Expected to be invaluable to scientists analyzing climate change Important for disaster response – earthquakes, floods, fires etc Data will also help design and enforce EU policies: fishing quotums etc Media captionPepijn Veefkind: “TROPOMI violates the reflected light up into thousands of colours”