Expected Performance of the EUSO-SPB2 Fluorescence Telescope

TL;DR

The paper evaluates the expected performance of the EUSO-SPB2 fluorescence telescope for detecting ultra-high-energy cosmic rays, including simulations, hardware development, and onboard software algorithms for future space missions.

Contribution

It provides detailed simulations and performance estimates for the EUSO-SPB2 fluorescence telescope, including trigger algorithms and detection thresholds for UHECRs.

Findings

Energy threshold estimated at 10^18.2 eV

Maximum detection rate at 10^18.6 eV

Development of onboard software with deep learning algorithms

Abstract

The Extreme Universe Space Observatory Supper Pressure Balloon 2 (EUSO-SPB2) is under development, and will prototype instrumentation for future satellite-based missions, including the Probe of Extreme Multi-Messenger Astrophysics (POEMMA). EUSO-SPB2 will consist of two telescopes. The first is a Cherenkov telescope (CT) being developed to identify and estimate the background sources for future below-the-limb very high energy (E>10 PeV) astrophysical neutrino observations, as well as above-the-limb cosmic ray induced signals (E>1 PeV). The second is a fluorescence telescope (FT) being developed for detection of Ultra High Energy Cosmic Rays (UHECRs). In preparation for the expected launch in 2023, extensive simulations tuned by preliminary laboratory measurements have been preformed to understand the FT capabilities. The energy threshold has been estimated at $10^{18.2}$ eV, and results in a maximum detection rate at $10^{18.6}$ eV when taking into account the shape of the UHECR spectrum. In addition, onboard software has been developed based on the simulations as well as experience with previous EUSO missions. This includes a level 1 trigger to be run on the computationally limited flight hardware, as well as a deep learning based prioritization algorithm in order to accommodate the balloon's telemetry budget. These techniques could also be used later for future, space-based missions.