Euclid: Precise inference of defocus wavefront error from image diffraction spike measurements

arXiv:2606.25625 · astro-ph.CO, astro-ph.IM · Submitted 2026-06-24 · Read on arXiv

D. Neumann, L. Miller, H. Hoekstra, K. Kuijken, I. H. Whittam, N. E. Chisari, R. Nakajima, B. Altieri, A. Amara, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, A. Basset, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, M. Kilbinger, R. Kohley, B. Kubik, M. Kunz, H. Kurki-Suonio, R. Laureijs, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, C. Moretti, L. Moscardini, C. Neissner, R. C. Nichol, S. -M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, G. D. Racca, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Schirmer, P. Schneider, T. Schrabback, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, A. Gregorio, A. Loureiro, M. Sereno

Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands · Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK · Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands · Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands · Department of Physics and Astronomy, University of the Western Cape, Bellville, Cape Town, 7535, South Africa · Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands · Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany · ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain · School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK · INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · Centre National d'Etudes Spatiales -- Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy · INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy · INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy · INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese · Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands · INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese · INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy · Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra · INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · INFN section of Naples, Via Cinthia 6, 80126, Napoli, Italy · Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA · Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain · Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK · Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK · ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain · Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France · Institut de Ciencies de l'Espai · UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France · Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK · Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France · Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland · ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain · INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France · Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France · School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK · Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · University Observatory, LMU Faculty of Physics, Scheinerstr.~1, 81679 Munich, Germany · Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain · Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany · INAF-Osservatorio Astronomico di Padova, Via dell'Osservatorio 5, 35122 Padova, Italy · Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.~1, 81679 München, Germany · Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway · Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA · Felix Hormuth Engineering, Goethestr. 17, 69181 Leimen, Germany · Cosmic Dawn Center · Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany · NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA · Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK · Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France · Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA · Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France · ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain · Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France · Université de Genève, Département de Physique Théorique and Centre for Astroparticle Physics, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland · Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland · Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands · Laboratoire d'etude de l'Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France · INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese · Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway · Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland · SKAO, Jodrell Bank, Lower Withington, Macclesfield SK11 9FT, UK · Centre de Calcul de l'IN2P3/CNRS, 21 avenue Pierre de Coubertin 69627 Villeurbanne Cedex, France · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany · INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy · Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3, Berkeley, USA · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy · Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne · Telespazio UK S.L. for European Space Agency · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra · School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK · European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands · Institut de Física d'Altes Energies · Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen, Denmark · Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada · European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands · INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy · Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France · Space Science Data Center, Italian Space Agency, via del Politecnico snc, 00133 Roma, Italy · Centre National d'Etudes Spatiales -- Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France · Institute of Space Science, Str. Atomistilor, nr. 409 Măgurele, Ilfov, 077125, Romania · European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands · Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA · INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany · Université St Joseph, Faculty of Sciences, Beirut, Lebanon · Departamento de Física, FCFM, Universidad de Chile, Blanco Encalada 2008, Santiago, Chile · INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy · Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany · Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany · Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstr. 25/8, 6020 Innsbruck, Austria · Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France · Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland · Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany · INFN-Padova, Via Marzolo 8, 35131 Padova, Italy · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy · Department of Physics, Royal Holloway, University of London, Surrey TW20 0EX, UK · INFN-Padova, Via Marzolo 8, 35131 Padova, Italy · Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra · Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK · Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal · Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK · Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark · European University of Technology EUt+, European Union · Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas · Institut de Recherche en Astrophysique et Planétologie · INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy · Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland · University Observatory, LMU Faculty of Physics, Scheinerstr.~1, 81679 Munich, Germany · Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy · Caltech/IPAC, 1200 E. California Blvd., Pasadena, CA 91125, USA · Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany · INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy · INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy · INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy · Astrophysics Group, Blackett Laboratory, Imperial College London, London SW7 2AZ, UK · INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy

astro-ph.CO, astro-ph.IM

Submitted: 2026-06-24

Comments: 19 pages, 12 figures, 3 tables, submitted to Astronomy & Astrophysics, comments welcome

Code: https://github.com/GalSim-developers/GalSim

License: http://creativecommons.org/licenses/by/4.0/

The gist: The success of the Euclid cosmological weak lensing measurements requires unprecedented knowledge of the point spread function (PSF) shape.

Terminology

Abstract

The success of the Euclid cosmological weak lensing measurements requires unprecedented knowledge of the point spread function (PSF) shape. Defocus wavefront errors induce variations in PSF size that directly bias inferred galaxy shapes. We present a rapid, model-independent estimator of the Euclid visible instrument defocus based on measuring subpixel shifts in diffraction spikes from bright stars, arising from the non-mirror-symmetric placement of the telescope spiders. This estimate requires no a-priori PSF model and can be directly inferred from individual survey exposures within seconds. We express defocus as the secondary mirror displacement along the optical axis, z, achieving a per-exposure precision of sigma(z) = 0.022, mu m in standard Euclid wide-survey images, corresponding to a peak-to-valley optical-path difference of 0.75, nm. This sensitivity resolves thermally induced shifts, typically 0.1-0.3, mu m, and enables tracking of temporal evolution and field-of-view variations when combining exposures within periods of stability. Since July 2024, the Euclid telescope has been exceptionally stable, while changes to defocus are effectively homogeneous across the field of view. By correlating defocus with PSF size, we find that the Euclid DR3 requirement of a fractional PSF size bias of R PSF 2/R PSF 2 <10-3 corresponds to field-averaged secondary mirror displacements exceeding z thr = (0.0683 plus or minus 0.0024), mu m. Our estimator provides a robust real-time monitoring tool, supplies a stringent prior for computationally intensive PSF model fitting, and is applicable not only to the Euclid telescope, but to other telescopes whose spider vanes are not mirror-symmetrically arranged.

Sources

Related papers