CTAO Instrument Response Functions: Comparison of prod5 and prod3b releases

The Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based observatory designed to study the universe at gamma-ray energies above 20 GeV. CTAO will comprise two observatories, one in the Northern hemisphere (La Palma, Spain) and one in the Southern hemisphere (Paranal, Chile). It is set to surpass any existing gamma-ray detector with its exceptional angular resolution, sensitivity, and wide energy range. The recently concluded pre-construction phase of CTAO saw several evolutionary versions of the planned observatory. During pre-construction phase, the observatory’s design changed continuously due to improvements of telescopes, detectors, changes following optimisation of the telescope layouts, and refined simulation and reconstruction algorithms. The introduction of the CTAO Alpha configuration for the installations freezes the number of telescopes and telescope types per observatory site for the first stage of CTAO construction. The CTAO Instrument Response Functions (IRFs) are derived from detailed Monte Carlo simulations and describe the expected performance of the observatory. CTAO makes its instrument response functions available to the scientific community in different file formats through the Zenodo portal (prod3b: see here; prod5: here). CTAO recommends to use whenever possible the newest release of instrument response functions (prod5). These provide the most realistic estimates for the performance of the observatory. This note compares the CTAO Instrument Response Functions between two design stages of CTAO captured by the prod3b and prod5 Monte Carlo simulation productions.