EUSO-A Space mission searching for Extreme Energy Cosmic Rays and neutrinos

The “Extreme Universe Space Observatory – EUSO” is an international, multi-agency mission, led by ESA, aimed at measuring from a Low Altitude Earth Orbiting Space Platform the flux and investigating the nature and origin of the charged and neutral particles of the Extreme Energy Cosmic Ray (EECR) with energy above the conventional value (E = 5x10^19 eV) of the Greisen Zatsepin and Kuzmin (GZK) effect EGZK =5x1019 eV). EUSO will pioneer the observation from Space of EECR-induced Extensive Air Showers (EASs), making measurements of the primary energy,arrival direction and possibly composition of the incoming flux by using a sensitive area and target volume far greater than achievable from the ground. Such data will shed light on the origin of EECRs, on their sources , on the propagation environment from the source to Earth on the particle physics mechanisms at energies well beyond the ones achievable in man-made accelerators. We will discuss in this paper the scientific motivations, the observational approach, the experimental set-up and the expected performances of the proposed mission.