The Cherenkov Telescope Array (CTA) is the next generation of ground-based observatory in the Very High Energy (VHE) gamma-ray domain. The observatory, operating in an open, all-sky mode, will consist of two sites, one in the Northern Hemisphere, at Observatorio Roque de los Muchachos (La Palma, Spain), and another in the Southern Hemisphere. CTA will implement Imaging Atmospheric Cherenkov Telescopes (IACTs) of large, medium and small size, mapping the VHE sky with an unprecedented sensitivity in an extended energy range. In its baseline design, 4 Large Size Telescopes (LSTs) will operate in coincidence in each site, dominating the CTA sensitivity in the 20 GeV - 150 GeV gamma-ray band, while the CTA core energy range, from 150 GeV to 5000 GeV, will be best covered by Medium Size Telescopes (MSTs), 25 in CTA-South and 15 in CTA-North.
Each LST will be based on a 23 m diameter segmented, light-weight reflector, incorporating an active mirror control system, and a fast Photo-Multiplier Tube (PMT) camera. These features will allow CTA to observe extragalactic sources up to redshifts larger than two and to improve the sensitivity in observing gamma-ray transients. A prototype LST is currently under construction at the CTA-North site. A commissioning and validation phase will follow, which will mark the beginning for the construction of the rest of the LSTs of CTA-North and CTA-South.
The MSTs, with an aperture of 10-12 m, are being explored in two different design options. One is based on the traditional IACT Davies-Cotton optical system and PMT-based cameras (FlashCAM and NectarCAM), which is perfected after the experience from current HESS, MAGIC and VERITAS observatories. An alternative approach, based on the novel Schwarzschild-Couder optical system and Silicon-Photo-Multiplier-based camera, is also being developed to improve angular resolution.
In this contribution, we will review the status of the prototypes of the LST and both MST for CTA.