What is the Large Size Telescope?


The Large-Sized Telescope (LST) is one of three types of telescopes to be built to cover the Cherenkov Telescope Arrays. LSTs arranged at the centre of both the northern and southern hemisphere arrays will cover the low-energy sensitivity between 20 and 150 GeV. Each LST is a giant 23 metre diameter telescope with a mirror area of about 400 square metres and a fine pixelized camera made of 1855 light sensors capable of detecting individual photons with high efficiency. Although the LST stands 45 metres tall and weighs around 100 tonnes, it is extremely nimble, with the ability to re-position within 20 seconds to capture brief, low-energy gamma-ray signals. Both the fast re-positioning speed and the low energy threshold provided by the LSTs are critical for CTA’s studies of transient gamma-ray sources in our own Galaxy and for the study of active galactic nuclei and gamma-ray bursts at high redshift.

The LST Collaboration, consists of more than 200 scientists from 11 countries: Brazil, Bulgaria, Croatia, France, Germany, India, Italy, Japan, Poland, Spain and Switzerland. The LST-1, the first telescope constructed on the CTA north site, was inaugurated in October 2018 and has been undergoing commissioning testing ever since.


How does LST Work?


The gamma rays that LST detects don’t make it all the way to the earth’s surface. When a gamma ray reaches the earth’s atmosphere it interacts with it, producing cascades of subatomic particles such as electrons and positrons. These high energy subatomic particles are moving so fast they produce a light equivalent of a sonic boom high in the atmosphere. This produces so called Cherenkov photons taking the form of a flash of pale blue light lasting only a billionth of a second. Only dozens of Cherenkov photons are created from a very high energy gamma-ray and in order to detect said photons a large and sensitive telescope, such as LST, is needed.

To better understand the initial gamma ray, data from several telescopes will be used to measure the brightness and direction of the Chrenekov flash. This information is digitized and combined with the other telescopes of CTA which is used by scientists to determine the origin and energy of the initial gamma ray. The data is reduced and sent to scientists around the world to study astronomical objects such as: pulsars, black holes, supernova remnants, and dark matter.

Further information about how LST and CTA work can be at following link:

How CTA will detect Cherenkov light


What is the Cherenkov Telescope Array?


The Cherenkov Telescope Array (CTA) is a global initiative to build the world’s largest and most sensitive high-energy gamma-ray observatory with tens of telescopes planned on two sites: one in the northern hemisphere on the island of La Palma, Spain, and the other in the southern hemisphere near Paranal, Chile. CTA will be the foremost global observatory for very high-energy gamma-ray astronomy over the next decade and beyond and will be the first ground-based gamma-ray astronomy observatory open to the world-wide astronomical and particle physics communities.

CTA will address some of the greatest mysteries in astrophysics, detecting gamma rays with an unprecedented sensitivity and expanding the cosmic source catalogue tenfold. CTA is a unique, ambitious large-scale infrastructure that will expand observations up to a region of the spectrum that has never been seen, opening an entirely new window to our Universe. The CTAO GmbH serves to prepare the design and implementation of the CTA Observatory. The CTAO works in close cooperation with the CTA Consortium composed of 1500+ members from 31 countries, which is responsible for directing the science goals of the Observatory and is involved in the design and supply of instrumentation. The CTAO is governed by a council of shareholders from 11 countries and one intergovernmental organization, as well as associate members from two countries.

Further information about CTA can be at following link:

The Cherenkov Telescope Array Observatory


A comprehensive description of the LST project and an updated status can be read here , here, and here