The Pierre Auger Observatory I: The Cosmic Ray En- ergy Spectrum and Related Measurements

The flux of cosmic rays above 10 eV has been measured with unprecedented precision at the Pierre Auger Observatory. Two analysis techniques have been used to extend the spectrum downwards from 3 × 10 eV, with the lower energies being explored using a unique technique that exploits the hybrid strengths of the instrument. The spectral features are presented in detail and the impact of systematic uncertainties on these features is addressed. The increased exposure of about 60% with respect to previous publications is exploited.