The FAAM aircraft is flying across the UK throughout January and February 2018 to measure ice clouds, for a research project called PICASSO. Ice clouds have an important role in the atmosphere, influencing its temperature and the formation of precipitation. Clouds, of all types, have a cooling effect on the global climate. This net cooling effect results from the opposing impacts from liquid clouds (which cool by reflecting sunlight back into space) and ice clouds (which warm through a “greenhouse” effect). However, there is a lack of understanding about many of the physical processes occurring in ice clouds. This is due to the complexity of ice particle processes and interactions between atmospheric motions, water vapour, and aerosol particles (solid or liquid particles suspended in the atmosphere). This means ice clouds are a source of significant uncertainty in climate models, and can lead to errors in weather forecasts. Establishing which climate and weather models are the most accurate remains difficult due to the lack of observations of ice cloud properties. Remote sensing techniques (e.g. radar) can provide observations of ice clouds over large areas on a continuous basis, making them ideal for assessing the models. However, these techniques do not typically measure the amount of condensed water in the air directly and can make assumptions about the properties of the ice clouds. The FAAM aircraft is being used to directly observe the ice cloud properties in-situ, and the data collected will be compared with results from several radars on the ground. This work will improve understanding of ice cloud properties, and lead to improved remote sensing measurements, both of which will improve climate model and weather forecasting accuracy.