33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE On-board calibration system of the JEM-EUSO mission

Abstract: In order to unveil the mystery of ultra-high energy cosmic rays (UHECRs), JEM-EUSO (Extreme Universe Space Observatory on-board Japanese Experiment Module) will observe extensive air showers induced by UHECRs from the International Space Station (ISS) orbit with a huge acceptance. Calibration of the JEM-EUSO instrument, which consists of Fresnel optics and a focal surface detector with 5,000 multi-anode photomultiplier tubes (MAPMTs), 300,000 channels in total, is very important to discuss the origin of UHECRs precisely with the observed results. The performance of the detector should always be monitored on orbit. Since the on-board resource is very limited, on-board calibration is in principle a relative one. For that purpose, a few uniform light sources with UV-LEDs and integrating spheres will be settled along the edge of the lens facing the focal surface (FS). Very uniform light is available thanks to the integrating sphere and the light intensity will be monitored in real-time by a photo diode attached to each sphere. The same light sources will be put along the edge of the FS and will illuminate the entrance pupil to monitor the transmission of the optics. The performance of the detector itself and the optics will be measured in the ISS days as required. The present development status of the calibration device will be reported together with the expected performance