Cosmic Rays at the Highest Energies – First Data from the Pierre Auger Observatory

The southern Pierre Auger Observatory, presently under construction in Malargüe, Ar-gentina, is nearing completion. The instrument is designed to measure extensive air-showers with energies ranging from 10 18-10 20 eV and beyond. It combines two complementary observation techniques; the detection of particles at ground and the coinci-dent observation of associated fluorescence light generated in the atmosphere above the ground. This is being realized by employing an array of 1600 water Cherenkov detectors, distributed over an area of 3000 km 2 , and operating 24 wide-angle Schmidt telescopes, positioned at four sites at the border of the ground array. The Observatory will reach its full size only in 2007 but data are routinely recorded already and have started to provide relevant science results. This talk will focus on the detector characterizations and presents first results on the arrival direction of extremely-high energy cosmic rays, their energy spectrum, and on the upper limit of the photon fraction.