JEM-EUSO is a new type of observatory that uses the earth's atmosphere as a detector. JEM-EUSO will be on orbit on the International Space Station (ISS). It observes transient luminous phenomena taking place in the earth's atmosphere caused by particles coming from space. The sensor is a super wide-field telescope that detects extreme energy particles with energy above 3×1019 eV. This remote-sensing instrument orbits around the earth every 90 minutes on board of the International Space Station at the altitude of approximately 400km (Figure 1-1). The figure shows an extreme energy particle colliding with a nucleus in the earth's Atmosphere, where it produces an Extensive Air Shower (EAS), consisting of numerous electrons, positrons, and photons. JEM-EUSO captures the moving track, which is revealed by the fluorescent UV photons and reproduces the energy development of the EAS.
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