Measurement of the Ultra High Energy Cosmic Ray Flux using Data of the Pierre Auger Observatory

The main objective of this thesis is the measurement of the cosmic ray energy spectrum above \unit[1]{EeV} based on the data recorded at the Pierre Auger Observatory. The continuation of the spectrum in the form of a power law is rejected with a 5.2 sigma significance. The number of events expected if a power law holds, above 40 EeV are 167+-3 and 35+- 1 above 100 EeV whereas in the measured flux there are 64 events and 1 event.