Modeling the Optical Cherenkov Signals by Cosmic Ray Extensive Air Showers Directly Observed from Sub-Orbital and Orbital Altitudes

TL;DR

This paper models optical Cherenkov signals from cosmic ray air showers observed from sub-orbital and orbital altitudes, estimating detection rates for upcoming space-based observatories to enhance high-energy cosmic ray studies.

Contribution

It introduces a customized computation scheme to predict Cherenkov signals and estimates event rates for balloon and satellite experiments like EUSO-SPB2 and POEMMA.

Findings

Expected event rates exceed hundreds per hour

Cherenkov detection from space is promising for high-energy cosmic rays

Provides a method to test and calibrate space-based Cherenkov detectors

Abstract

Future experiments based on the observation of Earth's atmosphere from sub-orbital and orbital altitudes plan to include optical Cherenkov cameras to observe extensive air showers produced by high-energy cosmic radiation via its interaction with both the Earth and its atmosphere. As discussed elsewhere, particularly relevant is the case of upward-moving showers initiated by astrophysical neutrinos skimming and interacting in the Earth. The Cherenkov cameras, by looking above Earth's limb, can also detect cosmic rays with energies starting from less than a PeV up to the highest energies (tens of EeV). Using a customized computation scheme to determine the expected optical Cherenkov signal from these high-energy cosmic rays, we estimate the sensitivity and event rate for balloon-borne and satellite-based instruments, focusing our analysis on the Extreme Universe Space Observatory aboard a Super Pressure Balloon 2 (EUSO-SPB2) and the Probe of Extreme Multi-Messenger Astrophysics (POEMMA) experiments. We find the expected event rates to be larger than hundreds of events per hour of experimental live time, enabling a promising overall test of the Cherenkov detection technique from sub-orbital and orbital altitudes as well as a guaranteed signal that can be used for understanding the response of the instrument.