The ESAF Reconstruction Framework of UHECR Events for the JEM-EUSO Mission

JEM-EUSO is a space based UV detector that will be mounted on the International Space Station (ISS) to monitor the earth's atmosphere searching for UHECR induced extended air showers (EAS). By evaluating the fluores- cence and Cherenkov signal on the focal surface of the instrument the arrival direction, energy and nature of the primary can be determined. Due to the instantaneous aperture of 10 5 km 2 sr JEM-EUSO will be able to measure several hundreds of events at energies higher than 5*10 19 eV. ESAF is a software for the simulation of space based UHECR detectors. It is configured to cover the specific aspects of the JEM-EUSO mission and to estimate its expected performance. ESAF can simulate every step of the generation and observation of an EAS - from the fluorescence track formation, the light transport in the atmosphere and through the instrument to the telemetry stage. The reconstruction chain covers the dis- crimination of the recorded track from background as well as the estimation of energy, arrival direction and Xmax for the determination of the UHECR species. In this paper we present strategies and algorithms implemented to estimate the spatial and energy resolution of JEM-EUSO as well as a selection of examples demonstrating the expected performance.