Optic detectors calibration for measuring ultra-high energy extensive   air showers Cherenkov radiation by 532 nm laser
  Calibration of a PMT matrix is crucial for the treatment of the data obtained with Cherenkov tracking detector. Furthermore, due to high variability of the aerosol abundance in the atmosphere depending on season, weather etc. A constant monitoring of the atmospheric transparency is required during the measurements. For this purpose, besides traditional methods, a station for laser atmospheric probing is used. 
Stanislav Knurenko, Yuri Egorov, Igor Petrov
astro-ph.IM