Sensors on polar orbiting satellites collect visible radiation reflected by the sea surface. The instruments acquire measurements non-stop along the satellite pass, across a wide swath of more than 2,000 kilometers. Complete coverage of the Earth is achieved every day. Data are recorded and stored on board the satellites until they pass over a ground station.

CLS starts processing raw data as soon as they are received from ground stations.

From the visible bands of the instrument, we estimate the phytoplankton concentration. A cloud mask is applied to identify the position of clouds on the images.