The technology behind the next generation very high-energy gamma-ray detector

»CTAO's three classes of telescope will cover a broad energy range from billions to trillions the energy of visible light.«

CTAO Technology

The CTAO is the next generation ground-based observatory for gamma-ray astronomy at very-high energies in the range from 20 GeV to 300 TeV. The CTAO’s detection of high-energy gamma rays is based on the imaging air Cherenkov technique (see How CTAO Works). Three classes of telescope are required to cover the full CTAO energy range (20 GeV to 300 TeV). For its core energy range (150 GeV to 5 TeV), the CTAO is planning up to 23 Medium-Sized Telescopes distributed over both array sites for the “Alpha Configuration“ (first construction phase). Up to four Large-Sized Telescopes and 37 Small-Sized Telescopes are planned to extend the energy range below 150 GeV and above 5 TeV, respectively. 

Image credit: Gabriel Pérez Diaz, IAC.

Once the mirrors reflect the light, the cameras capture and convert it into data. Each telescope has its own variation of camera, but the designs are all driven by the brightness and short duration of the Cherenkov light flash. The cameras are sensitive to these faint flashes and use extremely fast exposures to capture the light. Photomultiplier tubes (PMTs) or silicon photomultipliers (SiPMs) will convert the light into an electrical signal that is then digitised and transmitted. The calibrated image data will be used to reconstruct the properties of individual gamma rays. The energy and arrival direction of the gamma rays will be provided to science users of the Observatory to make spectra, lightcurves and images of astrophysical objects.

CTAO Performance


The CTAO will provide a very wide energy range and excellent angular resolution and sensitivity in comparison to any existing gamma-ray detector. Energies up to 300 TeV and an unprecedented resolution will push the CTAO to the edges of the known electromagnetic spectrum, providing a completely new view of the sky. To learn more about the CTAO’s expected baseline performance based on detailed Monte Carlo simulations of the facility, go to the CTAO Performance page.