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 Physics , 2009, DOI: 10.1088/1367-2630/11/6/065009 Abstract: JEM-EUSO is a space science mission to explore extreme energies and physics of the Universe. Its instrument will watch the dark-side of the earth and will detect UV photons emitted from the extensive air shower caused by an Ultra-High Energy Cosmic Rays (UHECRs above 10^18 eV), or Extremely High Energy Cosmic Ray (EHECR) particle (e.g., above about 10^20 eV). Such a high-rigidity particles as the latter arrives almost in a straight-line from its origin through the magnetic fields of our Milky Way Galaxy and is expected to allow us to trace the source location by its arrival direction. This nature can open the door to the new astronomy with charged particles. In its five years operation including the tilted mode, JEM-EUSO will detect at least 1,000 events with E>7x10^19 eV with the GZK cutoff spectrum. It can determine the energy spectrum and source locations of GZK to super-GZK regions with a statistical accuracy of several percent. JEM-EUSO is planned to be deployed by H2 Transfer Vehicle (HTV) and will be attached to the Japanese Experiment Module/ Exposure Facility (JEM/EF) of International Space Station. JAXA has selected JEM-EUSO as one of the mission candidates of the second phase utilization of JEM/EF for the launch in early-to-mid 2010s.
 Physics , 2011, DOI: 10.7529/ICRC2011/V03/0120 Abstract: The JEM-EUSO mission explores the origin of the extreme energy cosmic rays (EECRs) above 100 EeV and explores the limits of the fundamental physics through the observations of their arrival directions and energies. It is designed to achieve an exposure larger than 1 million km^2 sr year to open a new particle astronomy channel. This super-wide-field (60 degrees) telescope with a diameter of about 2.5 m looks down from space onto the night sky to detect near UV photons (330-400nm, both fluorescent and Cherenkov photons) emitted from the giant air showers produced by EECRs. The arrival direction map with more than five hundred events will tell us the origin of the EECRs and allow us to identify the nearest EECR sources with known astronomical objects. It will allow them to be examined in other astronomical channels. This is likely to lead to an understanding of the acceleration mechanisms, perhaps producing discoveries in astrophysics and/or fundamental physics. The comparison of the energy spectra among the spatially resolved individual sources will help to clarify the acceleration/emission mechanism, and also finally confirm the Greisen-Zatsepin-Kuz'min process for the validation of Lorentz invariance up to {\gamma}~10^{11}. Neutral components (neutrinos and gamma rays) can also be detected as well, if their fluxes are high enough. The JEM-EUSO mission is planned to be launched by a H2B rocket about JFY 2015-2016 and transferred to ISS by H2 Transfer Vehicle (HTV). It will be attached to the Exposed Facility external experiment platform of "KIBO".
 Physics , 2014, DOI: 10.1016/j.nima.2014.07.033 Abstract: In many applications, such as the detection of ultra-high energy cosmic rays using the air fluorescence method, the number of photons incident on the detector must be known. This requires a precise knowledge of the absolute efficiency of the photodetectors used. We present an experimental setup for measuring the single photoelectron gain and efficiency of multi-anode photomultipliers with a total uncertainty on the order of a few percent. This precision is obtained by using a comparison to a NIST calibrated photodiode, and the presented method can be applied to both vacuum photomultiplier tubes and other photodetectors. This work is motivated by the need to calibrate the focal surface of the EUSO-Balloon instrument, which is a technical pathfinder for the future JEM-EUSO mission. A complete discussion of photomultiplier calibration is presented and the efficiency measurement technique is discussed in detail. Example results are given to illustrate the key points of the method.
 The JEM-EUSO Collaboration Physics , 2013, Abstract: Contributions of the JEM-EUSO Collaboration to the 33rd International Cosmic Ray Conference (The Astroparticle Physics Conference) Rio de Janeiro, July, 2013.
 Astrophysics and Space Sciences Transactions (ASTRA) , 2011, DOI: 10.5194/astra-7-167-2011 Abstract: The Extreme Universe Space Observatory on JEM/EF (JEM-EUSO) is a space mission to study extremely high-energy cosmic rays. The JEM-EUSO instrument is a wide-angle refractive telescope in the near-ultraviolet wavelength region which will be mounted to the International Space Station. Its goal is to measure time-resolved fluorescence images of extensive air showers in the atmosphere. In this paper we describe in detail the main features and technological aspects of the focal surface of the instrument. The JEM-EUSO focal surface is a spherically curved surface, with an area of about 4.5 m2. The focal surface detector is made of more than 5000 multi-anode photomultipliers (MAPMTs). Current baseline is Hamamatsu R11265-03-M64. The approach to the focal surface detector is highly modular. Photo-Detector-Modules (PDM) are the basic units that drive the mechanical structure and data acquisition. Each PDM consists of 9 Elementary Cells (ECs). The EC, which is the basic unit of the MAPMT support structure and of the front-end electronics, contains 4 units of MAPMTs. In total, about 1 200 ECs or about 150 PDMs are arranged on the whole of the focal surface of JEM-EUSO.
 Physics , 2015, DOI: 10.1051/epjconf/20158902007 Abstract: An Atmospheric Monitoring System (AMS) is a mandatory and key device of a space-based mission which aims to detect Ultra-High Energy Cosmic Rays (UHECR) and Extremely-High Energy Cosmic Rays (EHECR) from Space. JEM-EUSO has a dedicated atmospheric monitoring system that plays a fundamental role in our understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. Our AMS consists of a very challenging space infrared camera and a LIDAR device, that are being fully designed with space qualification to fulfil the scientific requirements of this space mission. The AMS will provide information of the cloud cover in the FoV of JEM-EUSO, as well as measurements of the cloud top altitudes with an accuracy of 500 m and the optical depth profile of the atmosphere transmittance in the direction of each air shower with an accuracy of 0.15 degree and a resolution of 500 m. This will ensure that the energy of the primary UHECR and the depth of maximum development of the EAS ( Extensive Air Shower) are measured with an accuracy better than 30\% primary energy and 120 $g/cm^2$ depth of maximum development for EAS occurring either in clear sky or with the EAS depth of maximum development above optically thick cloud layers. Moreover a very novel radiometric retrieval technique considering the LIDAR shots as calibration points, that seems to be the most promising retrieval algorithm is under development to infer the Cloud Top Height (CTH) of all kind of clouds, thick and thin clouds in the FoV of the JEM-EUSO space telescope.
 Physics , 2013, Abstract: The Extreme Universe Space Observatory is an experiment to investigate the highest energy cosmic rays by recording the extensive air showers they create in the atmosphere. This will be done by recording video clips of the development of these showers using a large high-speed video camera to be located on the Japanese Experiment Module of the International Space Station. The video clips will be used to determine the energies and arrival directions of these cosmic rays. The accuracy of these measurements depends on measuring the intrinsic luminosity and the direction of each shower accurately. This paper describes how the accuracy of these measurements will be tested and improved during the mission using a global light system consisting of calibrated flash lamps and lasers located deep in the atmosphere.
 Astrophysics and Space Sciences Transactions (ASTRA) , 2011, DOI: 10.5194/astra-7-477-2011 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.
 Physics , 2015, DOI: 10.1051/epjconf/20158903001 Abstract: The origin of cosmic rays have remained a mistery for more than a century. JEM-EUSO is a pioneer space-based telescope that will be located at the International Space Station (ISS) and its aim is to detect Ultra High Energy Cosmic Rays (UHECR) and Extremely High Energy Cosmic Rays (EHECR) by observing the atmosphere. Unlike ground-based telescopes, JEM-EUSO will observe from upwards, and therefore, for a properly UHECR reconstruction under cloudy conditions, a key element of JEM-EUSO is an Atmospheric Monitoring System (AMS). This AMS consists of a space qualified bi-spectral Infrared Camera, that will provide the cloud coverage and cloud top height in the JEM-EUSO Field of View (FoV) and a LIDAR, that will measure the atmospheric optical depth in the direction it has been shot. In this paper we will explain the effects of clouds for the determination of the UHECR arrival direction. Moreover, since the cloud top height retrieval is crucial to analyze the UHECR and EHECR events under cloudy conditions, the retrieval algorithm that fulfills the technical requierements of the Infrared Camera of JEM-EUSO to reconstruct the cloud top height is presently reported.
 Physics , 2014, DOI: 10.1007/s10686-014-9378-1 Abstract: The JEM-EUSO observatory on board of the International Space Station (ISS) is a proposed pioneering space mission devoted to the investigation of Ultra High Energy Cosmic Rays (UHECRs). Looking downward at the earth's atmosphere with a 60$^\circ$ Field of View (FoV), the JEM-EUSO telescope will detect the fluorescence and Cherenkov UV emission from UHECR induced Extensive Air Showers (EAS) penetrating in the atmosphere. The capability of reconstructing the properties of the primary cosmic ray depends on the accurate measurement of the atmospheric conditions in the region of EAS development. The Atmospheric Monitoring system of JEM-EUSO will continuously monitor the atmosphere at the location of the EAS candidates and between the EAS and the JEM-EUSO telescope. With an UV LIDAR and an Infrared (IR) Camera the system will monitor the cloud cover and retrieve the cloud top altitude with an accuracy of $\sim$ 500 m and the optical depth profile of the atmosphere with an accuracy of $\Delta\tau \leq$ 0.15 and a resolution of 500 m. In this contribution the Atmospheric Monitoring system of JEM-EUSO will be presented. After a brief description of the system, the capability to recover the cloud top height and optical depth and to reconstruct the shower profile will be shown based on satellites data and simulation studies.
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