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

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 ${0.5}^{\mathrm{\prime }\mathrm{\prime }}$ 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.