K. Paterson, M Schirmer, K. Okumura, Bram Venemans, K. Jahnkę, N Aghanim, B. Altieri, A. Amara, S. Andreon, C. Baccigalupi, Marco Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, Andrea Bonchi, E. Branchini, M. Brescia, J. Brinchmann, S Camera, G Cañas-Herrera, V. Capobianco, J. Carretero, Santiago Casas, 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, A. Da Silva, R. da Silva, H. Degaudenzi, G. De Lucia, Di Giorgio AM, J. Dinis, H. (H) Dole, F. Dubath, X. Dupac, S. Dusini, A Ealet, S. Escoffier, Marcelo Farina, R. Farinelli, F Faustini, S. Ferriol, F. Finelli, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, P. Franzetti, S. Galeotta, K George, W. Gillard, B. Gillis, C. Giocoli, J. Gracia-Carpio, B. R. Granett, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, P. Hudelot, M. Jhabvala, E. Keihänen, S. Kermiche, A Kiessling, R Kohley, B. Kubik, M Kümmel, M. Kunz, H. Kurki‐Suonio, A.M.C Le Brun, D Le Mignant, S Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, K. Markovič, M. Martinelli, N. Martinet, F. Marulli, R Massey
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).