This is one of the first images from Sentinel-3A’s Sea and Land Surface Temperature Radiometer (SLSTR). Acquired with the instrument’s visible channels on 3 March 2016 at 11:23 GMT, this false-colour image features the Spanish Canary Islands, the Portuguese island of Madeira and the northwest coast of Africa. The vegetated islands appear red in contrast to Western Sahara, which has little vegetation. The snow-capped peak of Mount Teide on the island of Tenerife is clearly visible. Both SLSTR and Sentinel-3’s Ocean and Land Colour Instrument, OLCI, will be used to monitor plant health. As the SLSTR scans Earth’s surface, it senses visible light and infrared light (heat) in a number of different spectral channels. The thermal infrared channels will soon be working when the instrument has finished outgassing water vapour. This is necessary because the infrared channels must be cooled to operate properly. The SLSTR will measure global sea- and land-surface temperatures every day to an accuracy of better than 0.3ºC.