UHE cosmic ray detection with the Pierre Auger observatory

The Pierre Auger Observatory has been designed to measure the energy spectrum, the arrival direction, and the mass composition of cosmic rays above 10
¹⁸
eV with a hybrid detector system. It will finally consist of an array of 1600 water-Cherenkov Surface Detectors (SD) on a 1.5 km triangular grid and 24 fluorescence telescopes (FD) in four stations on the perimeter of the 3000 km
²
experimental area. The Observatory is at present under construction in the Pampa Amarilla near the town of Malarguumle - Province of Mendoza, Argentina. The construction of this Southern site will be completed in early 2006. We present the hybrid design of the Observatory (SD, FD), the current status of construction and the performance of the detector gained during regular operation in the installation phase. Since mid 2004, the first half of the FD telescopes have been installed and more than one quarter of the SD array has been deployed. The Observatory will be complemented by a Northern site in Utah or Colorado to achieve uniform full sky coverage