Lenka Tomankova Karlsruhe

Optical properties of the Auger fluorescence telescopes(pdf)

The Pierre Auger Observatory is primarily designed to study ultra-high-energy cosmic rays and comprises 27 fluorescence telescopes and an array of more than 1600 surface detectors. The energy scale of the experiment is derived from the fluorescence telescopes, making the understanding of their optical properties of paramount importance. The point-spread-function (PSF) has been measured using a remotely-flown platform carrying a point-like isotropic light source in the field of view of the telescopes. Different optical processes shape the PSF, including multiple reflections and dust on optical surfaces, causing about 18% of light arriving at the aperture to fall outside of the mean light collection region used in shower reconstruction. After a brief introduction to the Auger fluorescence telescopes, the methods for measuring the PSF and experimentally verifying the different contributions will be presented.