ESA’s Aeolus wind mission will provide timely and accurate profiles of the world’s winds and further information on aerosols and clouds. The mission will advance our understanding of atmospheric dynamics. It will also provide much-needed information to improve weather forecasts and contribute to climate research. The satellite carries a single instrument: a Doppler wind lidar called Aladin. This sophisticated instrument is designed to probe the lowermost 30 km of the atmosphere along the satellite’s orbital path. Comprising a powerful laser, a large telescope and a very sensitive receiver, Aladin is the first wind lidar in space. In cloud-free air the lidar will probe the atmosphere down to the surface of Earth, or to the top of dense cloud. Atmospheric phenomenon, such as the formation of large-scale turbulent flows triggered by obstacles or through atmospheric instability can be sensed by the Aeolus instrument. For example, Aeolus can sense ‘Karman streets’, which form when the air flows around an isolated mountain, modulating a cloud-field downstream and visible as repeating swirling pattern.