Estimating the angular resolution of the Extreme Universe Space Observatory (EUSO) using a modified version of the Pierre Auger Observatory fluorescence detector reconstruction framework

Abstract

The origins and nature of Ultra-High Energy Cosmic Rays (UHECRs), charged particles with energies greater than [10^{18}]{eV}, remain largely a mystery. One reason for this the extremely low flux at the highest energies (less than one particle per square kilometer per century). The largest current UHECR detector is the Pierre Auger Observatory, which spans over [3000]{km^2}. The principle detection method is based on measuring Extensive Air Showers induced by UHECRs interacting with the atmosphere. Using the Extreme Universe Space Observatory (EUSO) on-board the International Space Station to utilize the atmosphere as the detector increases the detection area by a factor of 50 over the Pierre Auger Observatory. The increase in detection area is only useful if the EAS energy and angular reconstructions are accurate enough compared to current detection methods. We have developed an independent angular reconstruction algorithm based on the methodology employed and proven at the Pierre Auger Observatory. The method is promising with some improvements over previous EUSO reconstructions as demonstrated by extending the analysis over the expected energy range of detection.