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 an ultraviolet laser and optical components 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 acts as a "test beam" that is used to investigate properties of the atmosphere and the air fluorescence detectors. Additionally, the laser can send a light pulse via optical fiber to the nearest surface detector tank. This signal, which occurs simulateously with light beamed into the sky, is used for the hybrid timing analysis of the surface and fluorescence detectors at the Observatory.