The JEM-EUSO Mission

The Extreme Universe Space Observatory (EUSO) on Japanese Experiment Module (JEM) is a science mission on the International Space Station (ISS) led by the Japan Aerospace eXploration Agency (JAXA) to investigate the nature and origin of Extreme Energy Cosmic Rays (EECR) beyond energy E0>7×1019 eV. The main objective of the mission is to perform charged-particle astronomy in this energy region by collecting a large sample of events (∼1000 events above E0) in 3-5 years of operation, measure their energy, arrival direction and composition with sufficient accuracy (ΔE<30%, Δang<2°, hadron/photon/neutrino separation ΔXmax<120g/cm2). With the above statistics, dozen of events per source are expected, which are enough to infer their energy spectrum. JEM-EUSO is a wide-angle telescope (field of view ±30°, integrated aperture >4×105km2⋅sr⋅yr) and consists of high-transmittance Fresnel lenses with a 2.5 m diameter, an advanced photo-sensitive detector at the focal surface and a suitable electronics. An infrared camera and a LIDAR system will be also used to monitor the earth's atmosphere. JEM-EUSO has been selected by JAXA as one of the mission candidates of the second phase utilization of JEM / Exposed Facility (JEM/EF) with launch expected in early 2010s and it is right now undertaking the Phase-A (concept study and technical feasibility). The scientific motivations of the mission, its objectives and expected performance are here summarized together with its links with other space-based projects such as Super-EUSO.