L'utilizzo del software ESAF per simulare la performance delle missioni future del programma JEM-EUSO

n this Thesis I report the results of simulations on the JEM¿EUSO future missions performances using the EUSO Simulation and Analysis Framework (ESAF). JEM- EUSO ("Joint Experiment Missions for Extreme Universe Space Observatory") is a space mission which aims, as main scientific goal, at the detection of extreme-high energy cosmic rays (EECRs). The JEM-EUSO concept consists in developing a super wide field telescope which will look down from space onto the Earth's atmosphere to detect UV photons emitted from air showers generated by the EECRs. In the first part of this Thesis I introduce the most relevant points of cosmic rays physics; after that, I describe more in detail the JEM-EUSO program, the ESAF software and the main pathfinders. In particular I show the results of ESAF simulations to evaluate some aspects of the performance of: EUSO-SPB2, Mini-EUSO and POEMMA.