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Lookup NU author(s): James NightingaleORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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).
Author(s): Euclid Collaboration
Publication type: Article
Publication status: Published
Journal: Astronomy and Astrophysics
Year: 2026
Volume: 707
Online publication date: 17/03/2026
Acceptance date: 18/07/2025
Date deposited: 08/04/2026
ISSN (print): 0004-6361
ISSN (electronic): 1432-0746
Publisher: EDP Sciences
URL: https://doi.org/10.1051/0004-6361/202555106
DOI: 10.1051/0004-6361/202555106
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