Speaker
Description
Ultra-high-energy cosmic rays (UHECRs) can be detected from space by observing the Earth’s limb, where the optical emission from extensive air showers (EASs) becomes accessible. Space-based observatories are also expected to play a pivotal role in the emerging era of multi-messenger astrophysics, in particular through the detection of Earth-skimming neutrinos. The validation of observational techniques for such extremely rare ultra-high-energy events relies on precursor missions such as NUSES, a satellite mission designed to operate in a Sun-synchronous, quasi-polar low Earth orbit.
Two scientific payloads will be integrated on board the satellite platform, developed by Thales Alenia Space-Italia (TAS-I): Terzina, which constitutes the primary subject of this work, and ZIRE, which is devoted to the study of low-energy cosmic rays and gamma rays, space weather phenomena, and magnetosphere-ionosphere-lithosphere coupling processes. Terzina is a compact Schmidt-Cassegrain Cherenkov telescope optimized to detect Cherenkov radiation produced by EASs in the Earth’s atmosphere. Its focal-plane camera, with a field of view of (7.2 deg) along the limb and (2.88 deg) across it, hosts an array of silicon photomultipliers (SiPMs). The instrument is designed to simultaneously observe the EASs initiated by UHECRs, looking above the limb, and the upward-going air showers induced by Earth-skimming neutrinos, looking below the limb.
To evaluate the performance of Terzina, a comprehensive Monte Carlo simulation chain has been developed, incorporating detailed Cherenkov signal modeling, trigger logic implementation, and particle interaction simulations. A central component of this framework is the optical validation performed with Geant4, employing OpticsLibSim, a library specifically developed to accurately reproduce the telescope’s optical response. Current studies focus on characterizing the instrument’s aperture and overall performance, with particular emphasis on its effective collection area and angular response, which are key observables for determining its sensitivity to UHECRs and neutrinos. The results obtained thus far support the robustness of the present design and provide a solid basis for the development of future large-scale space-based observatories dedicated to ultra-high-energy astroparticle physics.