JWST MIRI flight performance: The Medium-Resolution Spectrometer

Context . The Medium-Resolution Spectrometer (MRS) provides one of the four operating modes of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST). The MRS is an integral field spectrometer, measuring the spatial and spectral distributions of light across the 5–28 µm wavelength range with a spectral resolving power between 3700 and 1300. Aims . We present the MRS’s optical, spectral, and spectro-photometric performance, as achieved in flight, and we report on the effects that limit the instrument’s ultimate sensitivity. Methods . The MRS flight performance has been quantified using observations of stars, planetary nebulae, and planets in our Solar System. The precision and…