Status and perspectives of the Pierre Auger cosmic ray observatory

The problem of the origin of Ultra High Energy Cosmic Rays, that is those with an energy of the Primary above 1019 eV, is a challenging one. The expected flux at those energies is around 1/yr/km2, thus requiring an unprecedented size of the detector in order to achieve consistent statistics. The Pierre Auger Observatory will be the largest cosmic ray detector ever built, consisting of two sites, one for each hemisphere, equipped with 1600 water Cherenkov detectors and four fluorescence detectors, covering each 3000 km 2. The combination of the two techniques, referred to as the hybrid technique, results in unprecedented accuracy in the reconstruction of the air showers. The concept has been validated with an Engineering Array of 32 water tanks and two fluorescence telescopes, during which the apparatus demonstrated very good performances. This paper will summarize the features of the data, the reconstruction methods and the strategy toward completion of the full Observatory