European cities during heatwave of 2019, ECOSTRESS images. Maps of the European cities of Rome, Italy (upper left), Madrid, Spain (upper right), Paris, France (lower left) and Milan, Italy (lower right), showing ECOSTRESS surface temperature images acquired in the early mornings of 27 and 28 June 2019, during a heatwave. The images have been sharpened to delineate key features such as airports. Airports and city centres are hotter than surrounding regions because they have more surfaces that retain heat. ECOSTRESS (Ecosystem Spaceborne Thermal Radiometer Experiment) launched to the International Space Station (ISS) on 29 June 2018. Its primary mission is to detect plant health by monitoring Earth's surface temperature.