Search for ultra-high energy cosmic rays from space: the JEM-EUSO program
The origin and nature of Ultra-High Energy Cosmic Rays (UHECRs) remain unsolved in contemporary astroparticle physics. To give an answer to these questions is rather challenging because of the extremely low flux of a few per km2 per century at extreme energies (i.e. E > 5×1019 eV). The central objective of the JEM-EUSO program, Joint Experiment Missions for Extreme Universe Space Observatory, is the realization of an ambitious space-based mission devoted to UHECR science. A super-wide-field telescope will look down from space onto the night sky to detect UV photons emitted from air showers generated by UHECRs in the atmosphere. The JEM-EUSO program includes several missions from ground (EUSO-TA), from stratospheric balloons (EUSO-Balloon, EUSO-SPB1, EUSO-SPB2), and from space (TUS, Mini-EUSO) employing fluorescence detectors to demonstrate the UHECR observation from space and prepare the large size missions K-EUSO and POEMMA. Thanks to the variety of its missions, the JEM-EUSO program offers the opportunity to investigate also other quite different scientific topics which range from neutrino science to fundamental physics, from meteor science to strange quark matter search, from atmospheric science (i.e. cloud coverage, study of Transient Luminous Events and airglow processes) to bio-luminescence and oceanography. The scientific objectives associated with the developing projects of the JEM-EUSO program, with emphasis to its interdisclipinary aspects and the technological achievements allowing them will be reviewed. A short history of the steps which led to this ambitous program will be mentioned as well.