MOONS-ESO spectrograph: status of the cryogenic opto-mechanical system for movable optics

Abstract

The construction of the Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument, the next generation multi object spectrograph for the VLT, is ongoing. This remarkable instrument will combine for the first time the 8 m collecting power of the VLT, 1001 optical fibers with individual robotic positioners and both medium and high resolution spectral coverage across the wavelength range 0.65μm to 1.8 μm. The cryogenic optical bench, with its dimension of 2x3.2 meters, is extremely huge and accommodates the three optical branches (H, RI, YJ bands) with two spectral resolutions: this has been made possible thanks to four sliding systems capable to move over 250 Kg of optics and mechanics at 90K. In this paper we describe the status of these opto-mechanical systems, placing emphasis to the performances and the solutions adopted to realize the sliding systems.