Large-Sized Telescope Prototype Records its First Light

On the night of 14-15 December 2018, the Large-Sized Telescope (LST) prototype recorded its first Cherenkov light on the northern site of the Cherenkov Telescope Array (CTA), located at the Instituto de Astrofísica de Canarias’ (IAC’s) Observatorio del Roque de los Muchachos (ORM), on the Canary island of La Palma.

Credit: LST Collaboration


The prototype, named LST-1, is expected to become the first telescope of the CTA Observatory after a design review to ensure it complies with performance requirements. The LST-1 will be one of four LSTs to be built on La Palma that will cover the low-energy sensitivity of CTA between 20 and 150 GeV. An additional four LSTs are planned for the Observatory’s southern hemisphere site located at the European Southern Observatory’s (ESO’s) existing Paranal Observatory in the Atacama Desert (Chile). 


Thirty-seven institutes from ten countries (Brazil, Croatia, France, Germany, India, Italy, Japan, Poland, Spain and Sweden) worked on the different subsystems that form the LST-1 and make it run. Construction on-site started with the foundation in January 2017 and continued throughout the year with the installation of the rail and bogie, necessary for the azimuth movement of the telescope, as well as the dish that holds the mirror. In 2018, the final structure came together with the installation of the mirrors, which form a reflective surface of 400 square meters, and the camera structure installation. The final component to be installed, the camera, is the brain of the telescope responsible for detecting the incoming light.

“It has been amazing. We have managed to deploy a really state-of-the-art 23 m Cherenkov telescope in only 15 months. This was only possible because the collaboration has pulled together, with a real team spirit. We hope this new telescope will be equally successful in exploring the extreme events in the very high-energy gamma-ray sky,” said Juan Cortina, physicist at CIEMAT (Madrid) and LST Co-Work Package Leader.  


“I think we have the right to be very proud about this telescope, it really turned out well. At the same time, there’s still a lot of work ahead: now it’s time to learn how it works and what we can do better,” added Daniel Mazin, physicist at MPI for Physics (Munich) and University of Tokyo and Work Package Manager of the LST. 


Now, the prototype needs to undergo a rigorous design review, which is expected to last around a year. This commissioning phase will allow scientists to verify that the design parameters of the structure and camera fulfill CTA requirements to achieve science goals, operational needs, safety standards, etc.  


Congratulations to the LST team!