# Status of the Large Size Telescopes of the Cherenkov Telescope Array

## TL;DR

This paper reviews the development, installation, and commissioning of the Large Size Telescopes for the Cherenkov Telescope Array, highlighting their design, capabilities, and initial performance results.

## Contribution

It provides an update on the status, technical specifications, and first commissioning results of the LSTs in the CTA project, a major advancement in gamma-ray astronomy infrastructure.

## Key findings

- First LST installed at CTA-North in 2018
- LSTs can reposition within 20 seconds for GRB follow-up
- Initial commissioning tests show promising performance

## Abstract

The Cherenkov Telescope Array (CTA) will consist of two arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs) at the northern and southern hemispheres. CTA will feature IACTs with mirrors of three different sizes optimized to cover different energy ranges. The proposed sub-arrays of four Large Size Telescopes (LST) at CTA-North and CTA-South target the lowest energy range between around 20 GeV and 100 GeV. Thanks to their low weight of around 110 tons the LSTs can move by 180 deg in azimuth in 20 seconds for Gamma Ray Burst (GRB) follow-up. An LST has a tessellated parabolic mirror of 23 m diameter equipped with a system of actuators to correct for gravity-induced deformations during data taking. Its low-weight 2 ton camera at the prime focus has a 4.5 deg diameter, 1855 high QE PMTs and an embedded readout with 1 GSps sampling speed designed for data acquisition rates exceeding 10 kHz. A fully equipped LST has been installed at the CTA-North site in 2018 and is expected to be finished commissioning during 2019. The remaining three LSTs in the north will be installed by 2022. We will review the status of the LSTs, describe the installation of the first LST and report on the first results of the commissioning tests.