Opto-Mechanical Design and realization of a Far-Infrared Grating Module for Future Space Missions

Future far-infrared space missions bridging the gap between JWST and ALMA will utilize low-resolution grating spectrometers. To fully exploit the astronomical potential these instruments require compact, cryogenic and wideband grating modules with a large telecentric field of view. We present the opto-mechanical design and realization of a multi-purpose Grating Module Bread-Board (GMBB). Our design features a modular configuration consisting of a diffraction-limited collimator unit and camera bay optics allowing for easy adaptation to different wavelength/dispersion combinations of grating and detector. The opto-mechanical design is monolithic, and implements highly accurate and reproducable kinematic mounts. We present the driving concepts, methodologies, and engineering solutions, with special emphasis to blazed grating developments, supported by optical verification results.