The Cherenkov Telescope Array Observatory (CTAO) is the next-generation facility for ground-based very-high-energy gamma-ray astronomy. It is overseen by the CTAO ERIC legal entity established in January 2025. This date marks the official start of the project construction. The observatory will operate as a proposal-driven, open-access facility, supporting the global scientific community.
With two sites, one in each hemisphere, CTAO will offer full-sky coverage and deliver an order-of-magnitude improvement in sensitivity over current instruments. It will cover a broad gamma-ray energy range from 20 GeV to 300 TeV.
CTAO-North is located on La Palma in the Canary Islands (Spain),
CTAO-South is situated in the Atacama Desert of northern Chile.
The CTAO is designed as an array of three types of Imaging Atmospheric Cherenkov Telescopes (IACTs), each optimized for a different energy range.
Large-Sized Telescopes (LSTs), with 23m mirrors, target the lowest energies (<100 GeV), where gamma rays are more abundant but produce faint Cherenkov light.
Small-Sized Telescopes (SSTs), with 4.3m mirrors, are suited for the highest energies, where gamma rays are rare but produce bright light—requiring many telescopes spread over a wide area. The SSTs have an innovative dual-mirror optical design.
Medium-Sized Telescopes (MSTs), with 12m mirrors, cover the core TeV energy range, serving as the observatory’s workhorses.
The CTAO layout consists of three concentric sub-arrays:
- A compact central group of LSTs (~100 m spacing),
- A middle ring of MSTs (covering <1 km², ~160 m spacing)
- An outer ring of SSTs (covering ~ 3 km² widely spaced at ~210–250 m) to maximize detection area at the highest energies.
For more information please refer to https://www.ctao.org/emission-to-discovery/
Main technical characteristics
- Gamma-ray FoV of 6 degree
- Differential sensitivity of 10-13 erg/cm2/s at 2 TeV in 50 hours of observations
- Differential sensitivity of 8 x 10-13 erg/cm2/s at 100 GeV in 50 hours of observations
- Differential sensitivity of 10-10 erg/cm2/s at 100 GeV on minutes timescales
- Angular resolution at the level of 0.02 degrees above 10 TeV
- Energy resolution below 10%
- Able to follow up an external science alert in less than 50”
- Able to issue a science alert in 30”
IRFs available at https://zenodo.org/records/5499840