Parallel soiling measurements for 4 mirror samples during outdoor exposure with TraCS

The upgraded version of the Tracking Cleanliness Sensor, the so-called TraCS4, which determines the real-time cleanliness and soiling rate of four mirror samples simultaneously is presented. Using this device, different materials can be intercompared at the site of interest which is the main advantage as the performance of anti-soiling-coatings is usually dependent on local weather conditions. A detailed uncertainty analysis of the TraCS4 device results in a cleanliness measurement uncertainty of about 0.019 cleanliness points. The uncertainty for the intercomparison of different materials is derived to be 0.012 cleanliness points. Exemplary soiling measurements with different anti-soiling and reference coatings at PSA are presented.