New methods to improve the decontamination of slitless spectra

¹ IRAP, Université de Toulouse, CNRS, CNES, 14 Av. Edouard Belin, 31400 Toulouse, France
² MatSim, Faculté des Sciences, Université Ibnou Zohr, BP 8106 Cité Dakhla, Agadir, Maroc

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 8 September 2025
Accepted: 15 December 2025

Abstract

This paper proposes four new methods to decontaminate spectra of stars and galaxies resulting from slitless spectroscopy used in many space missions such as Euclid. These methods are based on two distinct approaches that simultaneously take into account multiple dispersion directions of light. The first approach, called the local instantaneous approach, is based on an approximate linear instantaneous model. The second approach, called the local convolutive approach, is based on a more realistic convolutive model that allows for the simultaneous decontamination and deconvolution of spectra. For each approach, a mixing model was developed to link the observed data to the source spectra. This was done either in the spatial domain for the local instantaneous approach or in the Fourier domain for the local convolutive approach. Four methods were then developed to decontaminate these spectra from the mixtures, exploiting the direct images provided by photometers. Test results obtained using realistic, noisy, Euclid-like data confirmed the effectiveness of the proposed methods.