The origins of ultra-high energy hadronic cosmic rays (UHECRs) remain an open question in astroparticle physics. Their spectrum between 10 PeV and 100 EeV is still affected by large statistical and systematic errors, as well as the determination of their composition. Direct detection of UHECRs is not possible in this energy range from high-altitude balloons or space-based experiments due to the exposure limitations; hence, detection is performed by large extensive air shower arrays extending over thousands of kilometres in desertic regions, like the Pierre Auger Observatory and the Telescope Array. Such detectors also proved sensitive to horizontal neutrinos beyond 10 PeV, a direction from which hadronic showers are highly suppressed. Observations from space offer access to much larger atmospheric volumes and could significantly increase the exposure to the highest-energy cosmic rays and neutrinos. While ambitious concepts such as POEMMA require large-aperture optics and sizeable satellites, compact instruments can provide an important pathfinder for these techniques.
NUSES is a satellite mission currently under development hosting two payloads, Zirè and Terzina. Terzina is a compact Cherenkov telescope designed to observe the fast optical emission from extensive air showers near the Earth's limb. It searches for downward-going showers produced by very-high-energy cosmic rays above the limb and upward-going showers initiated by Earth-skimming neutrinos below it. Its focal plane is equipped with Silicon Photomultipliers (SiPMs), providing the fast response and sensitivity required to detect faint, nanosecond-scale Cherenkov signals.
This seminar presents the status of the NUSES mission and of the Terzina payload, its main design features and scientific objectives, and simulation studies performed to assess its expected performance.