A1 Refereed original research article in a scientific journal
Euclid VI: NISP-P optical ghosts; 
Authors: Paterson, K.; Schirmer, M.; Okumura, K.; Venemans, B.; Jahnke, K.; Aghanim, N.; Altieri, B.; Amara, A.; Andreon, S.; Baccigalupi, C.; Baldi, M.; Balestra, A.; Bardelli, S.; Battaglia, P.; Biviano, A.; Bonchi, A.; Branchini, E.; Brescia, M.; Brinchmann, J.; Camera, S.; Cañas-Herrera, G.; Capobianco, V.; Carretero, J.; Casas, S.; Castellano, M.; Castignani, G.; Cavuoti, S.; Chambers, K. C.; Cimatti, A.; Colodro-Conde, C.; Congedo, G.; Conselice, C. J.; Conversi, L.; Copin, Y.; Courbin, F.; Courtois, H. M.; Da Silva, A.; da Silva, R.; Degaudenzi, H.; De Lucia, G.; Di Giorgio, A. M.; Dinis, J.; Dole, H.; Dubath, F.; Dupac, X.; Dusini, S.; Ealet, A.; Escoffier, S.; Farina, M.; Farinelli, R.; Faustini, F.; Ferriol, S.; Finelli, F.; Fotopoulou, S.; Fourmanoit, N.; Frailis, M.; Franceschi, E.; Franzetti, P.; Galeotta, S.; George, K.; Gillard, W.; Gillis, B.; Giocoli, C.; Gracia-Carpio, J.; Granett, B. R.; Grazian, A.; Grupp, F.; Guzzo, L.; Haugan, S. V. H.; Hoekstra, H.; Holmes, W.; Hormuth, F.; Hornstrup, A.; Hudelot, P.; Jhabvala, M.; Keihänen, E.; Kermiche, S.; Kiessling, A.; Kohley, R.; Kubik, B.; Kümmel, M.; Kunz, M.; Kurki-Suonio, H.; Le Brun, A. M. C.; Le Mignant, D.; Ligori, S.; Lilje, P. B.; Lindholm, V.; Lloro, I.; Mainetti, G.; Maino, D.; Maiorano, E.; Mansutti, O.; Marcin, S.; Marggraf, O.; Markovic, K.; Martinelli, M.; Martinet, N.; Marulli, F.; Massey, R.; McCracken, H. J.; Medinaceli, E.; Mei, S.; Meneghetti, M.; Merlin, E.; Meylan, G.; Mora, A.; Moresco, M.; Moscardini, L.; Nakajima, R.; Neissner, C.; Nichol, R. C.; Niemi, S.-M.; Nightingale, J. W.; Padilla, C.; Paltani, S.; Pasian, F.; Pedersen, K.; Percival, W. J.; Pettorino, V.; Pires, S.; Polenta, G.; Poncet, M.; Popa, L. A.; Pozzetti, L.; Raison, F.; Rebolo, R.; Renzi, A.; Rhodes, J.; Riccio, G.; Romelli, E.; Roncarelli, M.; Rossetti, E.; Saglia, R.; Sakr, Z.; Sánchez, A. G.; Sapone, D.; Sartoris, B.; Schewtschenko, J. A.; Schneider, P.; Schrabback, T.; Secroun, A.; Sefusatti, E.; Seidel, G.; Seiffert, M.; Serrano, S.; Simon, P.; Sirignano, C.; Sirri, G.; Stanco, L.; Steinwagner, J.; Tallada-Crespí, P.; Tavagnacco, D.; Taylor, A. N.; Tereno, I.; Toft, S.; Toledo-Moreo, R.; Torradeflot, F.; Tutusaus, I.; Valenziano, L.; Valiviita, J.; Vassallo, T.; Verdoes Kleijn, G.; Veropalumbo, A.; Wang, Y.; Weller, J.; Zacchei, A.; Zamorani, G.; Zinchenko, I. A.; Zucca, E.; Allevato, V.; Ballardini, M.; Bolzonella, M.; Bozzo, E.; Burigana, C.; Cabanac, R.; Calabrese, M.; Casenove, P.; Di Ferdinando, D.; Escartin Vigo, J. A.; Gabarra, L.; Matthew, S.; Mauri, N.; Metcalf, R. B.; Nucita, A. A.; Pezzotta, A.; Pöntinen, M.; Porciani, C.; Scottez, V.; Tenti, M.; Viel, M.; Wiesmann, M.; Akrami, Y.; Andika, I. T.; Anselmi, S.; Archidiacono, M.; Atrio-Barandela, F.; Bertacca, D.; Bethermin, M.; Blanchard, A.; Blot, L.; Borgani, S.; Brown, M. L.; Bruton, S.; Calabro, A.; Cappi, A.; Caro, F.; Carvalho, C. S.; Castro, T.; Chary, R.; Cogato, F.; Conseil, S.; Cooray, A. R.; Cucciati, O.; Davini, S.; De Paolis, F.; Desprez, G.; Díaz-Sánchez, A.; Di Domizio, S.; Diego, J. M.; Dimauro, P.; Enia, A.; Fang, Y.; Ferguson, A. M. N.; Ferrari, A. G.; Finoguenov, A.; Franco, A.; Ganga, K.; García-Bellido, J.; Gasparetto, T.; Gautard, V.; Gaztanaga, E.; Giacomini, F.; Gianotti, F.; Gozaliasl, G.; Gregorio, A.; Guidi, M.; Gutierrez, C. M.; Hall, A.; Hartley, W. G.; Hemmati, S.; Hernández-Monteagudo, C.; Hildebrandt, H.; Hjorth, J.; Kajava, J. J. E.; Kang, Y.; Kansal, V.; Karagiannis, D.; Kiiveri, K.; Kirkpatrick, C. C.; Kruk, S.; Le Graet, J.; Legrand, L.; Lembo, M.; Lepori, F.; Leroy, G.; Lesgourgues, J.; Leuzzi, L.; Liaudat, T. I.; Liu, S. J.; Loureiro, A.; Macias-Perez, J.; Maggio, G.; Magliocchetti, M.; Mannucci, F.; Maoli, R.; Martín-Fleitas, J.; Martins, C. J. A. P.; Maurin, L.; Miluzio, M.; Monaco, P.; Montoro, A.; Moretti, C.; Morgante, G.; Nadathur, S.; Naidoo, K.; Natoli, P.; Navarro-Alsina, A.; Nesseris, S.; Passalacqua, F.; Patrizii, L.; Pisani, A.; Potter, D.; Quai, S.; Radovich, M.; Reimberg, P.; Risso, I.; Sacquegna, S.; Sahlén, M.; Sarpa, E.; Schneider, A.; Schultheis, M.; Sciotti, D.; Sellentin, E.; Sereno, M.; Shulevski, A.; Smith, L. C.; Stadel, J.; Tanidis, K.; Tao, C.; Testera, G.; Teyssier, R.; Tosi, S.; Troja, A.; Teyssier, R.; Tosi, S.; Troja, A.; Tucci, M.; Valieri, C.; Venhola, A.; Vergani, D.; Verza, G.; Vielzeuf, P.; Walton, N. A.; Euclid Collaboration
Publisher: EDP Sciences
Publication year: 2026
Journal: Astronomy and Astrophysics
Article number: A226
Volume: 707
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202555106
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://doi.org/10.1051/0004-6361/202555106
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523408130
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
The Near-Infrared Spectrometer and Photometer (NISP) on board Euclid includes several optical elements in its path that introduce artefacts into the data from non-nominal light paths. To ensure uncontaminated source photometry, these artefacts must be accurately accounted for. This paper focuses on two specific optical features in NISP's photometric data (NISP-P): ghosts caused by the telescope's dichroic beamsplitter, and the bandpass filters within the NISP fore-optics. Both ghost types exhibit a characteristic morphology and are offset from the originating stars. The offsets are well modelled using 2D polynomials; only stars brighter than approximately 10 magnitudes in each filter produce significant ghost contributions. The masking radii for these ghosts depend on both the source-star brightness and the filter wavelength, ranging from 20 to 40 pixels. We present the final relations and models used in the near-infrared (NIR) processing function (PF) to mask these ghosts for Euclid's Quick Data Release (Q1).
Keywords:
instrumentation: photometers, space vehicles: instruments
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Funding information in the publication:
The authors at MPIA acknowledge funding by the German Space Agency DLR under grant number 50 QE 2303. We thank Pierre-Antoine Frugier for providing useful comments to improve the publication. The plots in this publication were prepared with Matplotlib (Hunter 2007). The Euclid Consortium acknowledges the European Space Agency and a number of agencies and institutes that have supported the development of Euclid, in particular the Agenzia Spaziale Italiana, the Austrian Forschungsförderungsgesellschaft funded through BMK, the Belgian Science Policy, the Canadian Euclid Consortium, the Deutsches Zentrum für Luft- und Raumfahrt, the DTU Space and the Niels Bohr Institute in Denmark, the French Centre National d’Etudes Spatiales, the Fundação para a Ciência e a Tecnologia, the Hungarian Academy of Sciences, the Ministerio de Ciencia, Innovación y Universidades, the National Aeronautics and Space Administration, the National Astronomical Observatory of Japan, the Netherlandse Onderzoekschool Voor Astronomie, the Norwegian Space Agency, the Research Council of Finland, the Romanian Space Agency, the State Secretariat for Education, Research, and Innovation (SERI) at the Swiss Space Office (SSO), and the United Kingdom Space Agency. A complete and detailed list is available on the Euclid web site (www.euclid-ec.org).
