Validation of the Real and Simulated Data of the Pierre Auger   Fluorescence Telescopes
  The fluorescence detector (FD) of the Pierre Auger Observatory is currently operating 18 fluorescence telescopes of the 24 that will be employed in the completed detector. These telescopes, grouped in 4 eyes each consisting of 6 telescopes, measure the longitudinal profile of cosmic ray showers with a 14% duty cycle. The reconstruction capability and triggering efficiency have been studied using a complete simulation and reconstruction production chain, employing both simulated CORSIKA showers and parameterised Gaisser-Hillas profiles. The propagation through the atmosphere and the detector response are taken into account and simulated in detail. These simulated data have been generated in a preliminary analysis using the method of importance sampling to efficiently cover the energy region of 0.3 - 300 EeV, various shower geometries and impact points and different primary particles. The distributions of observables have then been investigated in both real and simulated data, facilitating the validation of the reconstruction and simulation software. Comparisons of real and simulated data are discussed and used to assess their impact on the data analysis. 
The Pierre Auger Collaboration: L. Perrone, et al.