Records show that, on average, global sea level rose by 3.2 mm a year between 1993 and 2018, but hidden within this average is the fact that the rate of rise has been accelerating over the last few years. Taking measurements of the height of the sea surface is essential to monitoring this worrying trend – and the Copernicus Sentinel-6 mission is on the way to being ready to do just this.

The mission will be a constellation of two identical satellites that are launched sequentially.

Over the next decade, the Copernicus Sentinel-6A and then Sentinel-6B satellites will, importantly, take the role as reference missions, picking up the task of continuing the long-term record of sea-surface height measurements that have so far been supplied by the French–US Topex-Poseidon and Jason missions.