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Methods and techniques for high-resolution spectro-polarimetry with current and future high-resolution telescopes: lessons learned and ways forward Free Conference is closed

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DKIST-EST-VTF

Hosted by Juan Manuel Borrero

Affiliation Institute for Solar Physics

Georges-Köhler-Allee 401a
79110 Freiburg

13.01.2026 - 15.01.2026

Organizing institutions

Institut für Sonnenphysik (KIS)

Main category Natural Sciences (Astrophysics and Astrononmy)

Conference/Workshop objectives

The Institute for Solar Physics (KIS) in Freiburg (Germany) is organizing a meeting focusing on the technical and instrumental aspects of the new generation of large aperture solar telescopes. With the arrival and upcoming commissioning of the Visible Tunable Filter (VTF), DKIST will be equipped with its full suite of first light instruments. Since its first light initiative in 2019 and subsequent Operations Commissioning Phase, DKIST Operations has overcome many challenges, some expected, others totally unforeseen, in order to bring DKIST to its peak performance. Meanwhile, in Europe, plans for EST continue with different funding proposals submitted over the past years. Similar initiatives are being taken by China (CGST) and India (NLST), with the former having very good prospects. We believe therefore that the moment is ripe to bring these communities together in order to exchange ideas and experiences on the design, construction and operation of such facilities. The meeting will address topics pertaining instrumental and technical questions (cameras, light distribution, image reconstruction, fringe removal, integral field units, polarization calibration/modulation, cavity errors, analysis tools and so forth). We hope to provide a forum where the challenges, lessons learned, trade-offs and possible solutions can be openly discussed.

Local organizing committee

Juan Manuel Borrero
Jozef Bruls
Saida Milena Díaz Castillo
Vigeesh Gangadharan
Ivan Milic
Sylvia Nadler
Hardi Peter
Matthias Schubert
Taras Yacobchuk

Scientific organizing committee (SOC)

Hardi Peter
Alexandra Tritschler
Jorrit Leenarts
Nazaret Bello González
Elena Khomenko
Juan Manuel Borrero

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Sessions

Session 1: Cameras for Solar observations
Session 2: Methods for Image Reconstruction
Session 3: Fabry-Pérots and Polarimetric Calibration
Session 4: Adaptive Optics (AO) and MCAO
Session 5: VTF and IFUs
Session 6: Current and Future facilities

Programme

Day 1 (13 January 2026)

Welcome
Session 1: Cameras for Solar observations
Session 2: Methods for Image Reconstruction

Day 2 (14 January 2026)

Session 3: Fabry-Pérots and Polarimetric Calibration
Session 4: Adaptive Optics (AO) and MCAO

Day 3 (15 January 2026)

Session 5: VTF and IFUs
Session 6: Current and Future facilities
Meeting summary and adjournment

Invited speakers

Andrés Asensio Ramos
Thomas Berkefeld
Jaime de la Cruz Rodríguez
Manuel Collados
Hans-Peter Doerr
Andre Fehlmann
Achim Gandorfer
Thomas Kentischer
Nagajaru K.
Haosheng Lin
Jun Lin
Mats Löfdahl
Michiel van Noort
Thomas Rimmele
Kamal Sant
Thomas Schad
Goran Scharmer
Dirk Schmidt
Matthias Schubert
Hector Socas Navarro
Sami Solanki
Friedrich Wöger

Wenda Cao

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Important dates

Registration deadline: 8 January 2026
Conference dates: 13 - 15 January 2026

Registration and payment information

Registration Fee: €210

The registration fee includes the conference dinner.

Once you have completed the registration process, you will receive a confirmation email with detailed information about the payment process (bank transfer details). Should there be a problem with the payment, please send an email to info@leibniz-kis.de.

Conference venue

Institut für Sonnenphysik (KIS)
Georges-Köhler-Allee 401a.
79110 Freiburg
https://www.leibniz-kis.de/de/kontakt/

Hotel information

Arrangements to be made by the participants.

Travel information

Arriving at KIS/Freiburg

By Air:
The nearest Airport is EuroAirport Basel-Mulhouse-Freiburg (↗ EuroAirport)
There is a shuttle bus from Basel Airport to Freiburg city center: (↗ Freiburger Reisedienst)
The service runs roughly every hour and takes approximately 1 hour. It is advisable to book a seat in advance.

By Train:
Freiburg (Breisgau) Hbf (↗ Deutsche Bahn) is the city's main train station located in the city center.
The station is well connected to major German cities (including Frankfurt Airport)
and European (Basel, Strasbourg, Paris, Zurich) by long-distance trains (ICE, IC, EuroCity, and FlixTrain).

Local transportation:
The institute can be reached via the Freiburg city's tram (↗ VAG Freiburg).
The nearest Tram station is Technische Fakultät on Line 4 of the network.
For walking directions to KIS from the Tram station check ↗ Google Maps Direction.

For Bike lovers:
Freiburg is a bicycle-friendly city with a great network of bike paths.
Check out Frelo (↗ Frelo Webpage) - Freiburg's bike-sharing system.
Bikes can be rented via the Frelo app at stations across Freiburg.
There is also a drop-point convenitently located next to the KIS building.

For more info about Freiburg, please check the Freiburg Tourism portal (↗ Freiburg Tourisim)

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Thomas Schad

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

115 views

Date of upload:

14.01.2026

Co-author:

Abstract:

This presentation discusses system polarimetry approachs at DKIST. It covers methods and lessons for large-aperture solar spectropolarimetry.

Christoph Kuckein

Session: Session 2: Methods for Image Reconstruction

132 views

Date of upload:

14.01.2026

Co-author:

Sergio J. González Manrique, Thomas Berkefeld, Andrés Asensio Ramos, Miguel Esteves

Abstract:

BBI is the broad-band imager from the Institute of Solar Physics (KIS) attached to the GREGOR telescope at Tenerife, Spain. Of special interest are the limb observations of prominences acquired with BBI and the new limb AO at GREGOR. We briefly present the challenges encountered during the data restoration of limb observations.

Sergio Javier González Manrique

Session: Session 1: Cameras for Solar observations

117 views

Date of upload:

15.01.2026

Co-author:

T. Berkefeld, A. Asensio Ramos, C. Kuckein, M. Esteves Perez, J. C. Trelles Arjona, M. Collados and KIS workshop team

Abstract:

Adaptive Optics (AO) developments enable new high-resolution solar observations, particularly near the solar limb where conventional systems face limitations. At the 1.5-m GREGOR telescope, a novel Hα-sensitive Wave Front Sensor (WFS) developed by KIS allows stable AO correction using chromospheric intensity structures, even off-limb in prominences. We present first performance results from the science verification campaign, combining Hα imaging from BBI and spectropolarimetry from GRIS. The results show improved image stability and correction quality, confirming the system’s potential for future limb and chromospheric studies.

Juan Manuel Borrero

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

108 views

Date of upload:

19.01.2026

Co-author:

A. Vicente Arevalo, I. Milic

Abstract:

Despite best calibration efforts, wavelength scanning instruments such as Fabry Perots, may present unreliable continuum calibration of the spectral lines. In multi line observations this may negatively impact the retrieval of the temperature stratification in the solar atmosphere. In this contribution we present a method to circumvent these issues when present.

David Jess

Session: Session 5: VTF and IFUs

109 views

Date of upload:

19.01.2026

Co-author:

Abstract:

Here, we present an IFU prototype that has been designed for operation within the near-ultraviolet to mid-optical wavelength range, which enables key spectral lines (e.g., Ca II H/K, H$\beta$ , Sr II, Na I D1/D2, etc.) to be studied, hence providing additional spectral coverage to the instrument suites developed to date. The IFU was constructed as a low-budget proof-of-concept for the upcoming 2m class Indian National Large Solar Telescope and employs circular cross-section fibres to guide light into a Czerny-Turner configuration spectrograph, with the resulting spectra captured using a high quantum efficiency scientific CMOS camera. Mapping of each input fibre allows for the reconstruction of two-dimensional spectral images, with frame rates exceeding 20 per second possible while operating in a non-polarimetric configuration. The science verification data presented here highlights the suitability of fibre-fed IFUs operating at near-ultraviolet wavelengths for solar physics research.

Jan Jurcak

Session: Session 2: Methods for Image Reconstruction

95 views

Date of upload:

19.01.2026

Co-author:

Abstract:

Long-term observational data series are essential for studying evolution of plasma parameters in solar atmosphere. However, the consistency and reliability of such analyses are often compromised by changing observing conditions over time. Plasma parameters that were found to be constant over long periods of time and in different manifestations of solar activity, e.g. constant vertical component of the magnetic field on the umbra-penumbra boundaries or equipartition field strength on the sunspot boundary, were discovered using data from space-based instruments. If ground-based data are used, the long term consistency might be missed due to the changing observing conditions. What mitigation strategies can we use to account for variable observing conditions?

Hans-Peter Doerr

Session: Session 5: VTF and IFUs

111 views

Date of upload:

19.01.2026

Co-author:

Abstract:

Spectrum restoration combines the benefits of grating spectrographs, an excellent spectral fidelity and a potentially wide spectral range, with the high angular resolution achievable with filter-based imaging instruments. The method is used with ground-based telescopes and has also been implemented for the SUSI instrument aboard Sunrise 3. This contribution briefly introduces the method and the benefits for the science, but focuses on the lessons learned from a series of setups that have been deployed to ground-based solar telescopes in the past. The insights gained from success and failure of those endeavors were condensed into the distinct concept and the design of the wide-band high-resolution imaging spectropolarimetric explorer (WHISPER) currently in development for the Goode Solar Telescope.

Mats Löfdahl

Session: Session 2: Methods for Image Reconstruction

108 views

Date of upload:

19.01.2026

Co-author:

Abstract:

Image restoration with MFBD methods, current status and possible future development. (Movies showing anisoplanatism missing from slides.)

Mats Löfdahl

Session: Session 2: Methods for Image Reconstruction

104 views

Date of upload:

19.01.2026

Co-author:

Abstract:

Because of anisoplanatism, MFBD image restoration of solar images is usually done on subfields of order 5 arcsec squared, and the results mosaicked into the larger field of view. However, the mosaicking introduces artifacts at high spatial frequences in the Fourier domain.

Göran Scharmer

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

107 views

Date of upload:

19.01.2026

Co-author:

M. Löfdahl, J. de la Cruz Rodríguez, B. Lindberg, J. Leenaarts, H. Socas-Navarro

Abstract:

We discuss how to optimise the science output of the European Solar Telescope (EST), when used without the wide-field compensation for high-altitude seeing that the EST multi conjugate adaptive optics (MCAO) will offer. This will likely be the mode of operating EST during its first year, following first light. In this mode, the spatial resolution of a much smaller telescope could surpass that of EST. We propose to operate EST in multi-aperture mode, which will, together with the use of short exposure times and image reconstruction techniques, dramatically improve image quality. In particular, the multi-aperture mode will provide the sustained stable high image quality needed for obtaining time sequences of spectropolarimetric data. The multi-aperture mode is implemented by optically segmenting the 4.2 m aperture into six 1.4 m subapertures by a low-cost modification of the camera lenses of the three Fabry-Perot systems that are expected to be operational soon after first light.

Göran Scharmer

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

110 views

Date of upload:

19.01.2026

Co-author:

B. Lindberg, J. de la Cruz Rodríguez, J. Leenaarts, P. Sütterlin, T. Hillberg, A.G. de Wijn, L. Rouppe van der Voort, C.Pietraszewski, M. Foster, J. Storey

Abstract:

We discuss the requirements, concepts, simulations, implementation, and calibration of two dual Fabry-Perot (FPI)-based imaging spectropolarimeters, CHROMIS and CRISP2 (which was recently installed), at the Swedish 1-m Solar Telescope. The overall design is made robust and stable by tailoring the low-resolution etalon reflectivity to accommodate expected cavity errors from both etalons, by using a compact optical design that eliminates the need for folding mirrors, and enclosing the entire system within a single container sealed by lenses. By using a telecentric design based on lenses rather than mirrors, image degradation by the FPI system is negligible and the throughput of the system is maximised. The initial alignment is greatly simplified. The telecentric design allows the full calibration of essential system parameters to be carried out without interfering with the optical set-up or the cameras. We put forward a proposal for a similar design for the European Solar Telescope.

Etienne Pariat

Session: Session 6: Current and Future facilities

118 views

Date of upload:

19.01.2026

Co-author:

Bernard Gelly

Abstract:

THEMIS, the French 1-m class solar telescope, has benefited from profound renovations and modification of its light path over the last 10 years. Thanks to a state-of-the art solar adaptive optics, THEMIS observations can now reach the diffraction limit at 0.15”, enabling to resolve details on the scale of 100 km on the Sun. In the last two years, THEMIS spectro-polarimetric mode has also been renewed and tested. Unprecedented observations are thus now being obtained by THEMIS. Upcoming evolutions of THEMIS, such as the reception and commissioning of a new synergic instrument, the renewed Italian “Interferometric BIdimensional Spectrometer (IBIS 2.0)” will also be discussed.

Andrés Asensio Ramos

Session: Session 2: Methods for Image Reconstruction

92 views

Date of upload:

20.01.2026

Co-author:

Abstract:

Different solutions to the multi-object multi-frame blind deconvolution problem using GPUs and AI are discussed.

Rolf Schlichenmaier

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

84 views

Date of upload:

20.01.2026

Co-author:

Abstract:

Mitigation by novel method to construct measured profile

Kamal Sant

Session: Session 3: Fabry-Pérots and Polarimetric Calibration

90 views

Date of upload:

02.02.2026

Co-author:

Ilaria Ermolli, Roberto Cirami, Fabrizio Giorgi, Mariarita Murabito, Teodora Mihailescu, Igor Coretti, Veronica Baldini, Paolo Di Marcantonio, Giovanna Jerse, Antonio Sulich, Giorgio Calderone, Valentina Alberti, Sara Bertocco, Luca Oggioni, Matteo Aliverti, Maurizio Oliviero, Fabiana Ferrente, Lidia Contarino, Paolo Romano, Salvatore Luigi Guglielmino, Giorgio Viavattene, Mauro Centrone, Giorgio Frazzoni, Fernando Pedichini, Roberto Piazzesi, Dario Del Moro, Luca Giovannelli, Bernard Gelly, Richard Douet, Etienne Pariat

Abstract:

The IBIS 2.0 project upgrades the Interferometric BIdimensional Spectrometer (IBIS, Cavallini 2006), which operated at the Dunn Solar Telescope (DST) of the National Solar Observatory (NSO) from 2003 to 2019. IBIS 2.0 is an etalon-based imaging spectropolarimeter consisting of two FPs in a classical mounting configuration for wavelength scanning, and an LCVR-based polarimetric modulation unit for polarimetry. The upgraded instrument is being mounted at the THEMIS solar telescope in the Canary Islands. Here we present a technical overview of the instrument.

Nagaraju Krishnappa

Session: Session 6: Current and Future facilities

91 views

Date of upload:

11.02.2026

Co-author:

NLST team

Abstract:

National Large Solar Telescope is a proposed state-of-the-art 2-meter telescope. Its primary goal is to conduct high resolution observations of the sun in visible and infra-red wavebands at high spatial, spectral and temporal resolutions combined with high polarimetric precision. This essentially demands for a telescope design with the least number of optical components necessary for achieving high througput. The telescope is planned to be installed next to the Pangong lake at an altitude of 4500 m. The high order adaptive optics will be an integral part of the telescope. To mitigate dome seeing, the NLST will operate with a fully open dome. The NLST’s post-focus instrumentation suite includes multi-wavelength broad-band and narrow-band imagers and a spectropolarimeter as first light instruments. More advanced back-end instruments will be added in the subsequent stages.

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First Name	Last Name	Affiliation
Juan Manuel	Borrero	Institute for Solar Physics
Pecador	Fistro	KIS
Vigeesh	Gangadharan	Institut für Sonnenphysik (KIS)
Jorrit	Leenaarts	Stockholm University
Elena	Khomenko	Instituto de Astrofisica de Canarias
Nazaret	Bello González	Institut für Sonnenphysik (KIS)
Juan Sebastian	Castellanos Duran	Max Planck Institute for Solar System Research (MPS)
Ivan	Milic	Institute for Solar Physics (KIS)
Franziska	Zeuner	IRSOL
Achim	Gandorfer	Max-Planck-Institut für Sonnensystemforschung
Jan	Jurcak	Astronomical Institute of the Czech Academy of Sciences
Tiago	Pereira	University of Oslo
Etienne	Pariat	THEMIS/FSLAC/CNRS
Andreas	Lagg	Max Planck Institute for Solar System Research
Nagaraju	Krishnappa	Indian Institute of Astrophysics
Shibu	Kunchandy Mathew	Udaipur Solar Observatory, Physical Research Laboratory
Markus	Roth	Thüringer Landessternwarte Tautenburg
Sami	Solanki	Max-Planck-Institute for Solar System Research
Jun	Lin	Yunnan Observatories, Chinese Academy of Sciences
Mats	Löfdahl	Stockholm University
Hans-Peter	Doerr	Thüringer Landessternwarte Tautenburg
Michael	Sigwarth	Thüringer Landessternwarte Tautenburg
Christoph	Kuckein	Instituto de Astrofisica de Canarias
Manuel	Collados	Instituto de Astrofisica de Canarias
Luis	Bellot Rubio	Instituto de Astrofísica de Andalucía-CSIC
Alexandra	Tritschler	National Solar Observatory
Hemanth	Pruthvi	Thüringer Landessternwarte
Alex	Feller	Max Planck Institute for Solar System Research
Thomas	Berkefeld	KIS
Alfred	de Wijn	NSF NCAR
Azaymi	Siu	Instituto de Astrofisica de Andalucia
Sergio Javier	González Manrique	Universidad de La Laguna
Wenda	Cao	Big Bear Solar Observatory
Hanna	Strecker	Instituto de Astrofísica de Andalucía (IAA-CSIC)
Philippe	Bourdin	University of Graz
Luca	Giovannelli	University of Rome Tor Vergata
David	Jess	Queen's University Belfast
Luc	Rouppe van der Voort	University of Oslo
Kamal	Sant	INAF - OAR
Jaime	de la Cruz Rodriguez	Stockholm University
Göran	Scharmer	Stockholm University
Rolf	Schlichenmaier	Institut für Sonnenphysik (KIS)
Mariarita	Murabito	INAF-Rome observatory
Harsh	Mathur	University of Oslo
Thomas	Schad	National Solar Observatory
Hector	Socas-Navarro	European Solar Telescope Foundation
Kevin	Reardon	National Solar Observatory
Thomas	Rimmele	NSO
Andrés	Asensio Ramos	Instituto de Astrofísica de Canarias
Hardi	Peter	Institut für Sonnenphysik (KIS)
Salvo	Guglielmino	Istituto Nazionale di Astrofisica (INAF) - OACT
Andre	Fehlmann	National Solar Observatory
Friedrich	Woeger	National Solar Observatory
Shahin	Jafarzadeh	Queen's University Belfast
Taras	Yakobchuk	Institut für Sonnenphysik (KIS)
Matthias	Schubert	Institut für Sonnenphysik
Reiner	Volkmer	Institut für Sonnenphysik
Saida Milena	Diaz Castillo	Institut fuer Sonnenphysik (KIS)
Michiel	van Noort	Max Planck Institute for Solar System Research
Francisco	Iglesias	MPS and CONICET
Renzo	Ramelli	Istituto ricerche solari Aldo e Cele Daccò (IRSOL)
ilaria	ermolli	INAF Osservatorio Astronomico di Roma