Status of the JEM-EUSO mission and studies of the instrumentʼs performance

The JEM-EUSO mission explores the origin of the extreme energy cosmic rays (EECRs) above 50 EeV through the observations of their arrival directions and energies. It is designed to open a new particle astronomy channel. This super-wide-field (60 degrees) telescope with a diameter of about 2.5m looks down from space onto the night sky to detect near UV photons (290–430nm, both fluorescent and Cherenkov emissions) produced by EECR-induced giant air showers. 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, and 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 and emission mechanisms, and also finally confirm the Greisen-Zatsepin-Kuzʼmin process for the validation of Lorentz invariance up to γ ∼ 10 11 . Neutral components (neutrinos and gamma rays) can be detected as well, if their fluxes are high enough. The JEM-EUSO mission is planned to be launched by a H2B rocket and transferred to ISS by H2 Transfer Vehicle (HTV). It will be attached to the Exposed Facility external experiment platform of Kibo.