νSpaceSim: A Comprehensive Neutrino Simulation Package for Space-based & Suborbital Experiments

We describe a new comprehensive, end-to-end simulation package for the modeling of the extensive air shower (EAS) signals from very-high energy (above a PeV) cosmic neutrinos applicable to sub-orbital and space-based observations. The goal is to provide an efficient and practical cosmic neutrino EAS signal generation modeling package to the community that will provide a standard to gauge the neutrino measurement performance of these experiments and aid in their development. The modeling will be performed in such a way to easily be used to provide the neutrino-induced EAS signals delivered to a specific altitude for a given instrumental field-of-view and orientation. In this paper, we discuss the modeling of tau neutrino interactions inside the Earth, propagating the τ-leptons into the atmosphere, modeling the decays, forming composite EASs, generating the air fluorescence, Cherenkov, and radio signals, and the propagation through the atmosphere. Future work on the modeling of atmospheric transmission and scattering effects will include consideration of the uncertainties and more robust modeling of atmospheric and UHECR backgrounds. Additionally, the framework will allow for the calculation of the sky coverage, the pointing requirements for target-of-opportunity follow up observations of transients, and the inclusion of different neutrino interaction cross-sections to allow for the modeling of non-standard physical processes.