The Pierre Auger Observatory: Challenges at the highest-energy frontier

AbstractThe Pierre Auger Observatory explores the highest-energy Universe, through the detection of air showers induced bythe most energetic cosmic rays, whose nature and origin remain enigmatic despite decades of study. Exciting progress is being accomplished in measuring the characteristics of these messengers with unprecedented statistics. Theirenergy spectra, their arrival directions, and the properties of the cascades they initiate are studied in an attempt toelucidate their nature (mass composition, possibility of gamma-ray or neutrino primaries), provenance andpropagation (sources, anisotropies, spectra). The scientific and technical challenges are extreme, and are addressed in a multiplicity of ways, including a program of enhancements to the base design of the Observatory. We review these challenges, the solutions implemented and under way, and their impact on the rich science harvest reaped by the project