This requires instruments capable of precise cloud measurement, which is particularly complex. Images, even multispectral ones, can identify only a part of their overall shape. So, in addition to the optical sensor (called MSI), EarthCARE is installing a specific radar that will be able to determine the precise internal structure of clouds: the Japanese CPR (Cloud Profiling Radar) instrument.
CPR will work with a third instrument, an ultraviolet LiDAR called ATLID that, thanks to laser radiation, can reconstruct the 3D shape of clouds. It was this sensor that was incredibly complex to build, but also to test. And French! A LiDAR of the same type (but with different characteristics) was carried by the ESA Aeolus mission, which measured wind profiles throughout the atmosphere. This applied research and industrial realization took almost a decade and pushed the entire mission schedule, doubling the final cost. The satellite was originally supposed to be delivered in 2018 and then in 2020!