The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l’Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

The European Solar Telescope

Funding Information: C.Q.N. was supported by the EST Project Office, funded by the Canary Islands Government (file SD 17/01) under a direct grant awarded to the IAC on ground of public interest. This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreements No 739500 (PRE-EST) and 653982 (GREST). This project was supported by the European Commission’s FP7 Capacities Programme under Grant Agreements No 212482 (EST Design Study) and No. 312495 (SOLARNET). It was also supported by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No. 824135 (SOLARNET). This work has been partially funded by the Spanish Ministry of Science and Innovation through project RTI2018-096886-B-C51, including a percentage from FEDER funds, and through the Centro de Excelencia Severo Ochoa grant SEV-2017-0709 awarded to the Instituto de Astrofísica de Andalucía in the period 2018-2022. The EST preparatory phase was supported by a grant for research infrastructures of national importance from the Swedish Research Council (registration number 2017-00625). J.J. was supported by the Ministry of Education, Youth and Sports of the Czech Republic through the EST-CZ project (LM2018095). C.K. acknowledges funding received from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 895955. Queen’s University Belfast acknowledges support from the Science and Technology Facilities Council (STFC) under grant No. ST/V003739/1. This work was supported by Fundação para a Ciência e a Tecnologia (FCT) through the research grants [UID/FIS/04434/2019], UIDB/04434/2020, UIDP/04434/2020, UIDB/00611/2020 and UIDP/00611/2020. This work was partly funded by a grant of the Austrian Science Fund (FWF): P 32958-N. J.C.R., C.J.D.B. and A.P.Y. gratefully acknowledge financial support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (SUNMAG, grant agreement 759548). J.A. was supported by Centre National d’Etudes Spatiales (CNES). G.A., M.C., L.F., V.H., A.O. and L.R.V.V acknowledge support by the Research Council of Norway through its Centres of Excellence scheme, project number 262622. L.B., M.B., R.R. acknowledge State Secretariat for Education, Research, and Innovation (SERI), Canton Ticino and Swiss National Science Foundation (grants 200020_184952, 200021_175997, CRSII5_180238) for the financial support. R. Brajša and D. Sudar acknowledge the support by the Croatian Science Foundation under project 7549 ‘Millimeter and submillimeter observations of the solar chromosphere with ALMA’. The NSO is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. The work of A.B. was partially supported by the programme ‘Excellence Initiative – Research University’ for years 2020–2026 for University of Wrocław, project no. BPIDUB.4610.15.2021.KP.B. E.S.C. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) through the Spanish State Research Agency, under Severo Ochoa Centres of Excellence Programme 2020-2023 (CEX2019-000920-S). L.F. and N.L. would like to acknowledge support from UK Research and Innovation Science and Technology Facilities Council grants ST/L006200/1 and ST/T000422/1. J.F. acknowledges visiting facilities at Rosseland Centre for Solar Physics (University of Oslo), in 2019. P. Gömöry, A.K. and J.R. were supported by the Science Grant Agency project VEGA 2/0048/20. I. Kontogiannis is supported by KO 6283/2-1 of the Deutsche Forschungsgemeinschaft (DFG). C.J.N. is thankful to the Science and Technology Facilities Council (STFC), for support received through grant ST/T00021X/1, and ESA, for support as an ESA Research Fellow. K.P. was supported by the Hungarian National Research, Development and Innovation Fund (grants no. NKFI K-128384 and TKP2021-NKTA-64). P.J.A. Simões acknowledges support from CNPq (contract 307612/2019-8). J.T.B. acknowledges the funding received from the European Research Council (ERC) under de European Union’s Horizon 2020 research and innovation programme (ERC Advanced Grant Agreement No. 742265). M.V. is supported by VE 1112/1-1 of the Deutsche Forschungsgemeinschaft (DFG). L.Q.Z. acknowledges that this work was supported by the National Natural Science Foundation of China (Grant No. 11727805, No. 1210030348). F.Z. acknowledges that this work was supported by the Italian MIUR-PRIN grant 2017APKP7T and by the Università degli Studi di Catania (Piano per la Ricerca Università di Catania 2020-2022, Linea di intervento 2). Publisher Copyright: ©The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in anatural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems.Peer reviewe