Development of tools and hardware and the execution of a measurement campaign for background light and atmosphere conditions for Quantum Key Distribution (QKD) at urban location (major cities and metropolitan areas) under ARTES 4.0 Space Systems for Safety and Security (4S) Strategic Programme Line. These measurement results are an important check point to validate the design of the SAGA system. The background light and atmosphere metrology activity has the following objectives : - Design and procure test setups for measuring the background light (sky background and artificial light pollution) of the sky in urban environments. - Design and procure test setups for measuring the atmospheric turbulence conditions at urban environment.- Executing a measurement campaign at differenturban environments (at least 10 distributed over Europe) at different times (covering varying weather conditions, time of the day and different seasons). - Analyzing the data and assessing the impact on the QKD key rate.