Pre-launch optical verification of the Euclid NISP instrument and comparison with simulated images

TL;DR

This paper evaluates the optical performance of the Euclid NISP instrument before launch through ground tests and simulations, confirming it meets mission specifications and validating the simulation models against real data.

Contribution

It provides the first comprehensive comparison between ground-based test images and simulated images for the Euclid NISP instrument, validating the optical performance and simulation accuracy.

Findings

NISP fulfills PSF and spectral resolution specifications.

Good agreement between real test images and simulations.

Validated the NISP optical simulation model.

Abstract

To characterise the NISP (Near-Infrared Spectrometer and Photometer) instrument optical capability before the launch of the \Euclid telescope to orbit, foreseen in 2023, data analysis of ground-based tests and Monte Carlo simulations that mimic the expected NISP performance were carried out. Pre-launch test data were analysed to assess the fulfilment of the mission specifications in terms of Point Spread Function (PSF), set at EE50(PSF)$\,\leq 0.3$ arcseconds, and with a spectral resolution below 16 angstroms per pixel. We also provide a first comparison between real images from the ground-based tests with simulated ones. We confirm the high optical quality of the NISP instrument, fulfilling the mission specifications in terms of PSF and spectral dispersion with a good agreement between the different test campaigns. We validated the PSF and spectral dispersion provided by the NISP simulator, a crucial aspect to validate the consistency between real and simulated images.