Atmospheric calibration of aerosols and clouds using LIDAR & FRAM devices, site's climatology and possibly data trigger rates in some form (e.g. Cherenkov Transparency Coefficient). Finally input from other devices (e.g. pyrometers) shouldn't be excluded in this stage. The usecases have been written but they should be definitely reviewed and updated. The uncertainty estimation of a number of approaches is on-going (or yet to be started) thus issues might be added/deleted/modified.