Euclid preparation: LXXVII. The NISP spectroscopy channel: 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, BG_E, covers the wavelength range 926–1366 nm at a spectral resolution (ℛ) of 440–900 for a 0.″5 diameter source with a dispersion of 1.24 nm px⁻¹. Two red grisms, RG_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.

Key words: instrumentation: spectrographs / space vehicles: instruments / techniques: imaging spectroscopy / techniques: spectroscopic / cosmology: observations

Publisher note: The article number in this series contained a typo. The Roman numeral in the subtitle was corrected on 25 March 2026.