Euclid. VI. NISP-P optical ghosts

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

Subject (DDC)

520 - Astronomie, Kartografie

Project

Event

Exhibition start date

Exhibition end date

Conference start date

Conference end date

Date of the last check

ISBN

ISSN

0004-6361
1432-0746

Language

English

Created during FHNW affiliation

Yes

Strategic action fields FHNW

Publication status

Published

Review

peer-reviewed

Open access category

Hybrid

License

Citation

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., et al. (2026). Euclid. VI. NISP-P optical ghosts. Astronomy & Astrophysics, 707, A226. https://doi.org/10.1051/0004-6361/202555106

Full item page