CTA

Cherenkov Telescope Array

An advanced facility for ground-based gamma-ray astronomy

The Two Arrays of the CTA Observatory

In order to provide full sky coverage, the CTA observatory will consist of two arrays: a southern hemisphere array, which covers the full energy range from about some 10 GeV to about 100 TeV to allow for a deep investigation of galactic sources, and of the central part of our Galaxy, but also for the observation of extragalactic objects. A northern hemisphere array, consisting of the low energy instrumentation (from some 10 GeV to ~1 TeV) complements the observatory and is dedicated mainly to northern extragalactic objects.

In a possible design scenario, the southern hemisphere array of CTA will consist of two types of telescopes with different mirror size in order to cover the full energy range. The low energy instrumentation might consist of 23-28 m telescopes with a moderate field of view (FoV) of the order of 3-4 deg, while the high energy instrumentation above about 100 GeV will be equipped with large cameras with up to 6-8 deg FoV, installed in 12-15 m telescopes. This will not only allow effective surveys of the galactic plane and the investigation of extended sources and diffuse radiation, but will also result in an improved high energy performance with an expected additional improvement in count rate with respect to small FoV instrumentation. The overall sensitivity is supposed to be better by a factor of 5-10 with respect to current instruments. The northern hemisphere array will consist of the low energy instrumentation only, and focuses on the observation of extragalactic objects. Details of the layout of the telescope arrays and on the technical implementation are still to be optimized. For future upgrades the implementation of high QE photon detectors might be envisaged, which possibly results in an even higher sensitivity.