The Sentinel-3 satellites carry a package of different instruments including the Sea and Land Surface Temperature Radiometer (SLSTR). This instrument measures global sea- and land-surface temperatures every day to an accuracy of better than 0.3 K. Continuing the legacy of Envisat’s Advanced Along Track Scanning Radiometer, it maintains a dual-view along-track-scanning approach and delivers measurements at a spatial resolution of 500 m for visible/near-infrared and short-wavelength infrared channels and at 1 km for the thermal infrared channels. Furthermore, SLSTR includes two dedicated thermal infrared channels that are optimised for active fire detection and fire radiative power measurement – important for Copernicus Emergency Response and Climate Services. This animation provides a technical view of the instrument and shows how light enters, how it is reflected and split on its way to the detectors.