Silicon immersion gratings for astronomical applications in the infrared for wavelengths between 1 and 10-microns will be developed for telescope projects requiring spectral resolutions between 1,000 and 100,000. Immersing the grating in Silicon, which as an index of refraction of 3.4 in the infrared will enable much higher solid-angle throughput or etendu than is now possible for an instrument of smaller volume and mass. Spectrographs used on telescopes must be moved during the observations; either swinging through the sky at a Cassegrain or equivalent focus or rotating at a Nysmyth platform (to compensate for rotating field during exposure). Large heavy instruments present serious engineering challenges for cryogenic operation. Use of silicon immersion gratings will enable lighter-weight higher-performance instruments for cutting edge scientific research. The first astronomical observations will be on the Lick 3-meter telescope. ***
