LEST (Large European Solar Telescope)

LEST (Large European Solar Telescope)
Name	LEST (Large European Solar Telescope)
Caption	Conceptual design of a large aperture solar telescope
Organization	European Solar Physics Consortium
Country	European Union
Location	Proposed sites in the Canary Islands and Chile (historic proposals)
Established	Proposed 1990s–2000s
Wavelength	Visible, near-infrared, ultraviolet
Diameter	~2–4 m (concept)
Type	Solar telescope, Gregorian/Ritchey–Chrétien concepts

LEST (Large European Solar Telescope) was a proposed large-aperture ground-based solar telescope conceived to advance high-resolution observations of the Sun. The project aimed to combine innovations in adaptive optics, polarimetry, and infrared instrumentation to address outstanding questions in solar magnetism, chromospheric dynamics, and heliospheric coupling. Proposals and studies for the telescope involved multiple European observatories, universities, and agencies seeking to position Europe at the forefront of solar physics facilities.

Overview

LEST was conceived as a next-generation facility to succeed instruments such as Swedish Solar Telescope, German Vacuum Tower Telescope, GREGOR (solar telescope), and to complement projects including Daniel K. Inouye Solar Telescope, European Solar Telescope, and spaceborne missions like Solar Dynamics Observatory, Solar and Heliospheric Observatory, and Hinode (satellite). The project engaged research institutions including European Southern Observatory, Instituto de Astrofísica de Canarias, Max Planck Society, Observatoire de Paris, University of Oslo, and Royal Observatory of Belgium while interacting with funding bodies such as European Commission, European Research Council, and national agencies like CNRS, DLR, STFC, and CSIC. LEST proposals emphasized synergy with consortia involved in Atacama Large Millimeter Array, Very Large Telescope, and Square Kilometre Array planning.

History and development

Initial conceptual studies for a large European solar telescope began in the 1990s with participation from Universidad de La Laguna, Instituto de Astrofísica de Canarias, Kiepenheuer Institute for Solar Physics, Instituto de Astrofísica de Canarias, University of Glasgow, and Leiden Observatory. Key workshops and conferences where LEST concepts were discussed included gatherings at European Week of Astronomy and Space Science, IAU General Assembly, and meetings organized by the Royal Astronomical Society. Technical reports and roadmaps referenced technology demonstrations at Obervatoire de la Côte d'Azur, Istituto Nazionale di Astrofisica, and Institut d'Astrophysique Spatiale. Competing and complementary initiatives such as European Solar Telescope influenced LEST’s consolidation, while collaborations with National Solar Observatory and Kiepenheuer Institut für Sonnenphysik shaped instrument priorities.

Design and technical specifications

Design studies explored classical and novel architectures referencing optical systems used by McMath–Pierce Solar Telescope, Swedish 1-m Solar Telescope, and GREGOR (solar telescope). The envisioned aperture was in the 2–4 metre class to enable diffraction-limited imaging at visible and near-infrared wavelengths. Key subsystems planned included adaptive optics drawing on developments from Lockheed Martin, multi-conjugate schemes inspired by European Southern Observatory work, high-resolution spectropolarimeters akin to instruments on Hinode (satellite) and CRISP (instrument), and infrared polarimeters similar to devices developed at National Solar Observatory. Thermal control concepts referenced research at Paul Scherrer Institute and designs tested at Observatorio del Teide. Instrumentation suites considered integral field units using technologies advanced by Max Planck Institute for Solar System Research, cryogenic detectors in collaboration with Fraunhofer Society, and wavefront sensors developed with ETH Zurich.

Scientific objectives and capabilities

LEST aimed to probe the solar photosphere, chromosphere, and low corona with unprecedented spatial, temporal, and polarimetric sensitivity to address topics central to researchers at Solar Physics Division (AAS), Royal Astronomical Society, and university groups across Cambridge University, Heidelberg University, Universitat de Barcelona, Utrecht University, and University of Oslo. Scientific goals included resolving magnetic flux emergence relevant to theories by Eugene Parker and Hannes Alfvén; testing models from Parker Solar Probe-inspired coronal heating hypotheses; studying sunspot fine structure examined in works by Thomas Rimmele and Bengt Larsson; and linking photospheric processes with heliospheric consequences observed by ACE (spacecraft), Ulysses (spacecraft), and Solar Orbiter. Observational capabilities intended to advance fields overlapping with studies by Jocelyn Bell Burnell-related radio astronomy groups and high-energy solar research from RHESSI teams.

Project organization and collaborators

Organizational frameworks proposed for LEST involved consortia models similar to European Southern Observatory governance, with involvement from national research councils such as CNRS, DFG, NWO, CERN-adjacent institutes, and universities including University of Cambridge, University of Oxford, Sorbonne University, and Università di Padova. Instrument development and management drew on expertise from Max Planck Society, Finnish Meteorological Institute, Instituto de Astrofísica de Canarias, Observatoire de Paris, and technical partners like Thales Group, Airbus Defence and Space, and Leonardo S.p.A.. Workshops and steering committees included participation of scientists with affiliations to University of Oslo, Istituto Nazionale di Astrofisica, Leibniz Institute for Astrophysics Potsdam, and agencies like European Space Agency.

Site selection and infrastructure

Site studies considered high-quality observing locations compared to established observatories such as Roque de los Muchachos Observatory, Teide Observatory, Cerro Paranal, Cerro Tololo Inter-American Observatory, and sites in Atacama Desert. Candidate regions evaluated atmospheric seeing and sky transparency referencing measurements from Instituto de Astrofísica de Canarias, European Southern Observatory, and National Astrophysics Research Institute of Thailand collaborations. Infrastructure planning included road and power access modeled after facilities at Cerro Paranal and La Silla Observatory, environmental and cultural assessments coordinated with local authorities in Canary Islands and Chilean regions governed by agencies like Gobierno de Canarias and Comisión Nacional de Investigación Científica y Tecnológica. Logistics and operations were to follow precedents set by European Southern Observatory and National Solar Observatory.

Future plans and timeline

Although LEST itself did not reach funding and construction, its studies influenced subsequent initiatives such as European Solar Telescope and guided proposals interacting with Daniel K. Inouye Solar Telescope schedules and Solar Orbiter science coordination. Future planning for European solar facilities continues within consortia hosting roadmaps at European Space Agency, European Research Council, and national academies like Royal Society and Académie des Sciences. Timelines for successor projects depend on approvals from entities including European Commission framework programmes and national funding agencies such as CNRS, DFG, and NWO; coordination with international partners like National Science Foundation and NASA remains a strategic component.

Category:Solar telescopes