The optical calibration system for the CTAO-South Large-Sized Telescope camera

The Cherenkov Telescope Array Observatory (CTAO) is the next-generation $\gamma$-ray observatory. CTAO foresees two observation sites, one located in the Northern Hemisphere (Canary Island of La Palma) and the other in the Southern Hemisphere (Atacama Desert in Chile), for observing $\gamma$-ray events coming from all over the celestial vault. Thanks to the CTA+ program, two Large-Sized Telescopes (LST) will be added to the baseline configuration of the CTAO Southern array of telescopes. The Cherenkov-imaging cameras of the LSTs are compounded of 1855 photomultiplier tubes (PMTs) covering a hexagonal area of around 4.5 m$^2$. Each camera is calibrated by a system, dubbed Camera Calibration Box (CCB) and placed at the center of the telescope mirror’s dish surface. The CCB illuminates the PMTs also during the observation time (100 Hz, interleaved flat-field events) with a uniform, intensity-selectable, and diffuse UV (355 nm) light. The CCB is especially designed to withstand the extremely harsh environmental conditions of the CTAO Southern site and to provide high accessibility and maintainability. This contribution presents the CCB's key and peculiar design characteristics, in particular the optical and the software interface design choices including the internal stable and high sensitivity photon flux monitoring system.

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Publication Details

Published
2025-09-24
DOI
https://doi.org/10.22323/1.501.0792
Primary Topic
Adaptive optics and wavefront sensing
Type
article
Field-Weighted Citation Impact
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article

The optical calibration system for the CTAO-South Large-Sized Telescope camera

Andrea Busatta, F. Lucarelli, Marco Mastrofini, L. A. Antonelli et al.
Adaptive optics and wavefront sensing
article

The optical calibration system for the CTAO-South Large-Sized Telescope camera

Andrea Busatta, F. Lucarelli, Marco Mastrofini, L. A. Antonelli, F. Dazzi, Alda Rubini, Michele Palatiello
article en

Abstract

The Cherenkov Telescope Array Observatory (CTAO) is the next-generation $\gamma$-ray observatory. CTAO foresees two observation sites, one located in the Northern Hemisphere (Canary Island of La Palma) and the other in the Southern Hemisphere (Atacama Desert in Chile), for observing $\gamma$-ray events coming from all over the celestial vault. Thanks to the CTA+ program, two Large-Sized Telescopes (LST) will be added to the baseline configuration of the CTAO Southern array of telescopes. The Cherenkov-imaging cameras of the LSTs are compounded of 1855 photomultiplier tubes (PMTs) covering a hexagonal area of around 4.5 m$^2$. Each camera is calibrated by a system, dubbed Camera Calibration Box (CCB) and placed at the center of the telescope mirror’s dish surface. The CCB illuminates the PMTs also during the observation time (100 Hz, interleaved flat-field events) with a uniform, intensity-selectable, and diffuse UV (355 nm) light. The CCB is especially designed to withstand the extremely harsh environmental conditions of the CTAO Southern site and to provide high accessibility and maintainability. This contribution presents the CCB's key and peculiar design characteristics, in particular the optical and the software interface design choices including the internal stable and high sensitivity photon flux monitoring system.

National Science Foundation, Sveučilište u Zagrebu, Comunidad de Madrid, Ministerio de Ciencia, Innovación y Universidades, Centres de Recerca de Catalunya, European Commission, Deutsche Forschungsgemeinschaft, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Fundação de Amparo à Pesquisa do Estado de São Paulo, Ministerstvo Školství, Mládeže a Tělovýchovy, Bundesministerium für Bildung und Forschung, Generalitat de Catalunya, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Max-Planck-Gesellschaft, Narodowe Centrum Nauki, Hrvatska Zaklada za Znanost, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Fundação Araucária, Centre National de la Recherche Scientifique, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Sveučilište Josipa Jurja Strossmayera u Osijeku, Junta de Andalucía, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Istituto Nazionale di Fisica Nucleare, Japan Society for the Promotion of Science, Consejo Superior de Investigaciones Científicas, Staatssekretariat für Bildung, Forschung und Innovation, European Regional Development Fund, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules, Institute for Cosmic Ray Research, University of Tokyo
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