Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes
Author:
Dominis Prester Dijana1ORCID, Ebr Jan2ORCID, Gaug Markus3ORCID, Hahn Alexander4ORCID, Babić Ana5ORCID, Eliášek Jiří2ORCID, Janeček Petr2ORCID, Karpov Sergey2ORCID, Kolarek Marta1ORCID, Manganaro Marina1ORCID, Mirzoyan Razmik4ORCID
Affiliation:
1. Faculty of Physics, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia 2. FZU—Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 18200 Prague, Czech Republic 3. Departament de Física and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain 4. FZU—Max Planck Institut fuer Physik, 80805 Munich, Germany 5. Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, 10000 Zagreb, Croatia
Abstract
Ground-based observations of Very High Energy (VHE) gamma rays from extreme astrophysical sources are significantly influenced by atmospheric conditions. This is due to the atmosphere being an integral part of the detector when utilizing Imaging Atmospheric Cherenkov Telescopes (IACTs). Clouds and dust particles diminish atmospheric transmission of Cherenkov light, thereby impacting the reconstruction of the air showers and consequently the reconstructed gamma-ray spectra. Precise measurements of atmospheric transmission above Cherenkov observatories play a pivotal role in the accuracy of the analysed data, among which the corrections of the reconstructed energies and fluxes of incoming gamma rays, and in establishing observation strategies for different types of gamma-ray emitting sources. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the Cherenkov Telescope Array Observatory (CTAO), both located on the Observatorio del Roque de los Muchachos (ORM), La Palma, Canary Islands, use different sets of auxiliary instruments for real-time characterisation of the atmosphere. In this paper, historical data taken by MAGIC LIDAR (LIght Detection And Ranging) and CTAO FRAM (F/Photometric Robotic Telescope) are presented. From the atmospheric aerosol transmission profiles measured by the MAGIC LIDAR and CTAO FRAM aerosol optical depth maps, we obtain the characterisation of the clouds above the ORM at La Palma needed for data correction and optimal observation scheduling.
Funder
University of Rijeka Croatian National Foundation Spanish UE, the German BMBF and MPG Departament de Recerca i Universitats de la Generalitat de Cataluny Ministry of Education, Youth and Sports of the Czech Republic, and regional funds of the European Union
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