This timelapse video shows the Sentinel-3B satellite being prepared for liftoff on 25 April 2018 from Plesetsk in Russia. Sentinel-3B joined its twin, Sentinel-3A, in orbit.

The pairing of identical satellites provides the best coverage and data delivery for Europe's Copernicus programme – the largest environmental monitoring programme in the world.

The satellites carry the same suite of cutting-edge instruments to measure oceans, land, ice and atmosphere.