Euclid preparation: The NISP spectroscopy channel, on ground performance and calibration

TL;DR

This paper details the design, ground testing, and calibration of the NISP spectroscopy channel for ESA's Euclid mission, ensuring its performance meets scientific requirements for cosmology.

Contribution

It presents the construction and ground calibration results of the NISP grisms, demonstrating their performance for the Euclid mission's spectroscopic observations.

Findings

Successful ground calibration of NISP grisms

Spectral resolution meets mission specifications

Diffraction-limited slitless spectroscopy achieved

Abstract

ESA's Euclid cosmology mission relies on the very sensitive and accurately calibrated spectroscopy channel of the Near-Infrared Spectrometer and Photometer (NISP). With three operational grisms in two wavelength intervals, NISP provides diffraction-limited slitless spectroscopy over a field of $0.57$ deg$^2$. A blue grism $\text{BG}_\text{E}$ covers the wavelength range $926$--$1366$\,nm at a spectral resolution $R=440$--$900$ for a $0.5''$ diameter source with a dispersion of $1.24$ nm px$^{-1}$. Two red grisms $\text{RG}_\text{E}$ span $1206$ to $1892$\,nm at $R=550$--$740$ and a dispersion of $1.37$ nm px$^{-1}$. We describe the construction of the grisms as well as the ground testing of the flight model of the NISP instrument where these properties were established.