Manufacturing and measurement of the MIRI spectrometer optics for the James Webb Space Telescope

The Mid-Infrared Instrument (MIRI) on the JWST, Hubble space telescope replacement, contains an integral field spectrometer utilising four integral field units (IFU). This paper introduces manufacturing and measurement techniques developed to produce the monolithic multi-mirror arrays which perform spatial splitting and reformatting of light within each IFU: the image slicers and re-imagers. Typical slicer components have 18-22 mirrors of 50 nm RMS form accuracy, 5 nm R-q roughness and relative spatial positioning between mirror facets to 20 pm. The paper provides data for the Verification Model slicers produced by Cranfield University for the JWST MIRI consortium.