The Copernicus Sentinel-1 mission takes us over the busy maritime traffic passing through the English Channel.

The two identical Copernicus Sentinel-1 satellites carry radar instruments, which can see through clouds and rain, and in the dark, to image Earth’s surface below. Here, hundreds of radar images spanning 2016 to 2018 over the same area have been, compressed into a single image.

The sea surface reflects the radar signal away from the satellite, making water appear dark in the image. This contrasts metal objects, in this case ships, which appear as bright dots in the dark water. Boats that passed the English Channel in 2016 appear in blue, those from 2017 appear in green, and those from 2018 appear in red.

Owing to its narrowness, as well as its strategic connection of the Atlantic Ocean and the North Sea, the Channel is very busy with east-west ship traffic. Because of the volume of vessels passing through daily, a two-lane scheme is used, in order to avoid collisions. The two lanes can easily be detected in the image.

Many vessels crossing at the narrowest part of the English Channel can be seen in the far right of the image. Connecting Dover in England to Calais in northern France, the Strait of Dover is another major route, with over 400 vessels crossing every day. The shortest distance across the Channel is just 33 km, making it possible to see the opposite coastline on a clear day.

The cities of London and Paris, other towns and buildings and even wind turbines in the English Channel are visible in white owing to the strong reflection of the radar signal.

This image is also featured on the Earth from Space video programme.