Improvements to aerosol attenuation measurements at the Pierre Auger Observatory

Abstract

Sound knowledge of the aerosol loading in the atmosphere above the Pierre Auger Observatory is essential for the accurate reconstruction of shower energy deposit profiles using the atmospheric fluorescence technique. The vertical aerosol optical depth is inferred from hourly measurements of the vertically-fired UV laser beams of the Observatory’s central laser facilities via two complementary techniques. We report on recent refinements made to these aerosol analysis techniques, and on verification of the resulting aerosol measurements through internal consistency checks using reconstructed air shower data. These analysis improvements include accounting for the shape of the aerosol scattering phase function, and the treatment of multiple scattered light from the laser beam. The cumulative effect of these improvements is a modest increase in the measured vertical aerosol optical depth above the Observatory. We will discuss the impact of this increase on the reconstruction of showers measured with the Observatory’s fluorescence detector.