On 3 May, an important milestone was achieved in the Northern Hemisphere Array site at the Instituto de Astrofísica de Canarias’ (IAC’s) Roque de los Muchachos Observatory (La Palma, Spain): the 18-tonne mirror dish structure of the LST-4 was successfully lifted onto its lower structure. This complex task required lifting the dish to a height of 18 meters above the ground, where it was securely placed with the help of a 200-tonne crane.

Until now, there was only the prototype of the Large-Sized Telescope (LST), the LST-1. And by early 2026 two more LSTs (LST-2 and LST-3) are expected to be constructed and assembled.

Each LST has a reflective surface of 400 m² that collects and focuses Cherenkov light into the camera, where 1,855 state-of-the-art photomultiplier tubes convert the light into electrical signals. Due to their large reflective surface, LSTs have an unparalleled collection area that enhances sensitivity at the lowest energies, significantly improving performance over the previous generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) for energies below 50 GeV. Despite their substantial size, weighing approximately 110 tonnes and standing 45 meters tall, the LSTs exhibit remarkable manoeuvrability. Recent tests with the LST-1 in February by MPP, IFAE, and LAPP confirmed their ability to swiftly position to any point in the sky in under 30 seconds, enabling the capture of transient, low-energy gamma-ray signals.

The LSTs are procured and constructed by the LST Collaboration for the CTAO.