Euclid Preparation. XXX. 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 deg2 . A blue grism BGE covers the wavelength range 926–1366 nm at a spectral resolution R = 373–500 for a 000 .5 diameter source with a dispersion of 1.24 nm px−1 . Two red grisms RGE span 1206 to 1892 nm at R = 470–630 and a dispersion of 1.37 nm px−1 . We describe the build of the grisms as well as the ground testing of the flight model of the NISP instrument where these properties were established. Key words. Cosmology – Euclid – Instrument – NISP – Spectroscopy – optic