The CTAO’s Northern Hemisphere Array

The CTAO’s northern hemisphere array or CTAO-North is located on the island of La Palma in the Canary Islands, Spain, at the Instituto de Astrofísica de Canarias’ (IAC’s) Observatorio del Roque de los Muchachos in Villa de Garafía. The site currently hosts the prototype of the CTAO’s Large-Sized Telescope, the LST-1. In addition to the telescope array, the CTAO will have an operations building and calibration devices on site, as well as an office at sea level. The sum of these facilities is known as the “Northern Station.”

While the southern hemisphere array will span from the medium to the high end of CTAO’s energy range, optimized for gamma-ray energies between 150 GeV to 300 TeV, the northern hemisphere array will focus on the low- and mid-energy ranges from 20 GeV to 5 TeV, which implies the specialization of the northern array in extragalactic physics. For this reason, the northern hemisphere site will not host any Small-Sized Telescopes (SSTs), which are tuned to capture the highest-energy gamma rays.

Array Configuration

The layout of the CTAO Northern array includes the geographical location of 13 telescopes distributed over an area of about 0.5 km²: four Large-Sized Telescopes (LSTs) and nine Medium-Sized Telescopes (MSTs), in addition to the operations building and the calibration and atmospheric characterization equipment. The prototype of an LST, the LST-1, was completed on site in October 2018 and is foreseen to become the CTAO’s first telescope once it has completed its commissioning and is accepted by the CTAO. This particular configuration, called the “Alpha Configuration,” is the result of a thorough optimization process to maximize the scientific performance of CTAO’s two arrays. The CTAO-North layout is contingent on the approval of the construction permits released by the local authorities on La Palma, which is being managed by the IAC on behalf of the CTAO Central Organisation.