Performances of JEM–EUSO: energy and X max reconstruction

The Extreme Universe Space Observatory (EUSO) on–board the Japanese Experimental Module (JEM) of the International Space Station aims at the detection of ultra high energy cosmic rays from space. The mission consists of a UV telescope which will detect the fluorescence light emitted by cosmic ray showers in the atmosphere. The mission, currently developed by a large international collaboration, is designed to be launched within this decade. In this article, we present the reconstruction of the energy of the observed events and we also address the X max reconstruction. After discussing the algorithms developed for the energy and X max reconstruction, we present several estimates of the energy resolution, as a function of the incident angle, and energy of the event. Similarly, estimates of the X max resolution for various conditions are presented.