The Central Laser Facility at the Pierre Auger Observatory
  The Central Laser Facility is located near the middle of the Pierre Auger Observatory in Argentina. It features a UV laser and optics that direct a beam of calibrated pulsed light into the sky. Light scattered from this beam produces tracks in the Auger optical detectors which normally record nitrogen fluorescence tracks from cosmic ray air showers. The Central Laser Facility provides a "test beam" to investigate properties of the atmosphere and the fluorescence detectors. The laser can send light via optical fiber simultaneously to the nearest surface detector tank for hybrid timing analyses. We describe the facility and show some examples of its many uses. 
F. Arqueros, J. Bellido, C. Covault, D. D'Urso, C. Di Giulio, P.   Facal, B. Fick, F. Guarino, M. Malek, J.A.J. Matthews, J....