The Cherenkov Telescope Array Observatory (CTAO): ongoing development of the world’s premier ground-based gamma ray observatory

The Cherenkov Telescope Array Observatory (CTAO) is the next generation ground-based observatory for gamma-ray astronomy at very high energies. With initially 64 telescopes across two sites, the CTAO will be the world's largest and most sensitive high-energy gamma-ray observatory over energies from 20GeV to 300TeV. With sites at the Roque de los Muchachos Observatory (ORM) on the island of La Palma (Spain) and a southern array at the European Southern Observatory Paranal site in Chile, the CTAO will provide full sky coverage. The CTAO will be one order of magnitude more sensitive than current arrays, have a wider field of view, and have unprecedented accuracy in its detection of highenergy gamma rays dramatically changing our ability to study high energy sources. Development of telescopes and observatory infrastructure for the CTAO is already underway. Three classes of telescope types spread over a large area are required to cover the full the CTAO very-high energy range, and development is underway on all types. Infrastructure is under construction at ORM and increasingly so at Paranal. With its inherent modular architecture, sub-arrays of the eventual final array configuration will become operational in late 2026 with a performance better than existing arrays. The CTAO will continue to increase in performance as more telescopes are added until final completion towards the end of the decade. The CTAO will be the first ground-based gamma-ray observatory open to the worldwide astronomical and particle physics communities as a resource for data from unique, high-energy astronomical observations.