Measuring Atmospheric Aerosol Attenuation at the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

Conferencia; 33rd International Cosmic Ray Conference; 2013

The Fluorescence Detector (FD) of the Pierre Auger Observatory provides a nearly calorimetricmeasurement of the primary particle energy, since the fluorescence light produced is proportional to the energydissipated by an Extensive Air Shower (EAS) in the atmosphere. For this reason, the FD is used to calibrate theabsolute energy scale of the Surface Detector (SD) by means of hybrid events. Of the major correction termsapplied to the FD, atmospheric transmission through aerosols has the largest time variation. The correspondingcorrection to an EAS energy can range froma few percent to more than 40%, depending on the aerosol attenuationconditions, the distance of the shower, and the energy. We report on 9 years of hourly aerosol optical depthprofile measurements, including revised statistical and systematic error estimates, that are propagated throughEAS reconstruction. To accumulate these hourly aerosol optical depth profiles, the Central Laser Facility (CLF)and the eXtreme Laser Facility (XLF) of the Auger Observatory generated more than 4 million laser tracks thatwere recorded by the FD telescopes. Finally we describe major upgrades in progress to the CLF and to theelastic LIDAR stations at the Pierre Auger Observatory. The main features of these complementary upgrades arediscussed together with the expected results of their applications.