The CTAO LST Collaboration has reached a significant milestone with the successful approval and closure of the telescope’s Critical Design Review (CDR). The CDR is a thorough, multi-disciplinary evaluation of the telescope’s design to ensure it meets all required specifications and functions for its proper operation. The completion was marked by the official release of the CDR document, signed by the CTAO Managing Director. This approval paves the way for the final acceptance and handover of the Large-Sized Telescopes (LSTs), which are currently under commissioning and construction at CTAO-North in La Palma (Spain), to the CTAO. 

The LST’s CDR process began in 2018 and involved the preparation of hundreds of documents by the LST Collaboration, culminating in a final review with the CTAO Central Organisation during a face-to-face meeting in Munich in late 2019. During this meeting, missing deliverables and processes were identified and agreed upon. The first major milestone was the completion of the common elements assessment by the end of 2021. This was followed by the successful completion and approval of the Failure Modes and Effects Analysis in 2022, and with the reliability report and verification finalised a year later. 

This achievement represents a collective effort, requiring dedication and cooperation from the entire LST Collaboration. Successfully completing the CDR demonstrates that the LST design adheres to the requirements and guidelines set forth by the CTAO Central Organisation. Throughout this process, the trust and collaboration between the Central Organisation and the LST System Engineering teams have grown stronger, further enhancing the partnership. 

While this milestone marks significant progress, much work remains. With LST-1 currently under commission in La Palma, the LST Collaboration is also focused on constructing the remaining three LSTs for the site. Aiming for completion by the end of 2025, construction is progressing as expected, with the recent installation of the arch supporting the camera in one of the telescopes being the latest achievement. 

Congratulations to the entire LST Collaboration, with special recognition for those who played a direct role in overcoming this demanding challenge!