With the BLUESKY mission, the scientists want to clarify, among other things, whether there is a correlation between the clear blue sky during the lockdown and the proportion of aerosol particles in the atmosphere. Aerosols are finely distributed, microscopically small particles in the air that also influence cloud formation. They scatter and absorb solar radiation and thus also have an impact on the climate, because they influence the radiation balance of the atmosphere. Aerosols are created, amongst other ways, during the combustion of fossil fuels.