The angular resolution of the JEM-EUSO mission: An updated view

Abstract

The Extreme Universe Observatory onboard the Japanese Experiment Module (JEM-EUSO) is a mission being developed to observe ultra high energy cosmic rays (UHECRs) from space. JEMEUSO consists of a wide field of view UV-telescope, assisted by an atmospheric monitoring system, designed to be mounted oboard the International Space Station. JEM-EUSO will observe the extensive air showers (EAS) induced by UHE cosmic particles with energies above 3-1019 eV by using the earth's atmosphere as a large detector. Due to the amount of monitored target volume JEM-EUSO is expected to reach an effective aperture of approx. 2-105 km2 sr. During its lifetime, the mission will measure several hundred events with E > 5-1019 eV significantly improving the statistics of the most energetic part of the spectrum above the observed cut-off. In the context of the JEM-EUSO Collaboration different mission profiles are being explored. A configuration actively investigated is a telescope, mainly based on the same technologies already employed in the baseline instrument, which can be launched with the SpaceX Falcon 9 rocket and transported to the ISS by the Dragon spacecraft. This new mission configuration allows a circular design of the optics which improves the performances. In this paper we present a brief study of the expected angular resolution of this new configuration.