Detecting ultra-high energy cosmic rays from space with unprecedented acceptance: objectives and design of the JEM-EUSO mission
26 Oct 2011
1INFN, Structure of Rome Tor Vergata, Via Della Ricerca Scientifica 1, 00133, Rome, Italy
2RIKEN Advanced Science Institute, Wako 351-0198, Japan
3University of Torino, Dept. of Physics and INFN, Structure of Torino, Italy
4Department of Physics, Konan University, Kobe 658-8501, Japan
5Marshall Space Flight Center, NASA, Huntsville, AL 35812, USA
6Department of Phisics, The University of Alabama in Huntsville, AL 35899, USA
7APC – AstroParticule et Cosm. CNRS: UMR7164-CEA-IN2P3 – Observ. de Paris, Univ. Denis Diderot – Paris VII, France.
8Inst. für Astronomie und Astrophysik, Kepler Center for Astro and Part. Physics, Eberhard Karls Uni. Tübingen, Germany.
9Instituto de Ciencias Nucleares (ICN), Universidad Nacional Autonoma de Mexico, Mexico D.F.
10University of Rome Tor Vergata, Dept. of Physics, Rome, Italy
11Aoyama Gakuin University, Dept. of Physics and Mathematics, Tokyo, Japan
13Department of Physics, Ewha Womans University, Seoul 120-750, Korea
Abstract. The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) of the International Space Station (ISS) is the first mission that will study from space Ultra High-Energy Cosmic Rays (UHECR). JEM-EUSO will observe Extensive Air Showers (EAS) produced by UHECRs traversing the Earth's atmosphere from above. For each event, the detector will make accurate measurements of the energy, arrival direction and nature of the primary particle using a target volume far greater than what is achievable from ground. The corresponding increase in statistics will help to clarify the origin and sources of UHECRs as well as the environment traversed during production and propagation. Possibly this will bring new light onto particle physics mechanisms operating at energies well beyond those achievable by man-made accelerators. The spectrum of scientific goals of the JEM-EUSO mission includes as exploratory objectives the detection of high-energy gamma rays and neutrinos, the study of cosmic magnetic fields, and tests of relativity and quantum gravity effects at extreme energies. In parallel JEM-EUSO will systematically perform observation of the surface of the Earth in the infra-red and ultra-violet ranges, studying also atmospheric phenomena (Transient Luminous Effects). The apparatus is a 2 t detector using Fresnel-based optics to focus the UV-light from EAS on a focal surface composed of about 6 000~multianode photomultipliers for a total of ~3 · 105 channels. A multi-layer parallel architecture has been devised to handle the data flow and select valid triggers, reducing it to a rate compatible with downlink constraints. Each processing level filters the event with increasingly complex algorithms using ASICs, FPGAs and DSPs in this order to reject spurious triggers and reduce the data rate.