MAVIS: preliminary mechanical design overview of the adaptive optics module

MAVIS is a Multi-Conjugate Adaptive Optics for the UT4 of VLT designed to deliver a corrected FoV to a spectrograph, an imager, and a visiting instrument. An optical bench is used to support the post focal relay optics, which include the ADC, a K-mirror, the DM, and the selector. Said bench also rigidly supports the calibration, the LGS module, the NGS module and the imager providing the maximum stability and repeatability during maintenance operations. The Adaptive Optics Module structure (AOMS) was rigidly connected to the Nasmyth platform structure via the Overall Mechanical Structure (OMS). The OMS also provides structural integrity for the Spectrograph sub-system while isolating it from the main enclosure. At this level the AOMS and the OMS have been merged in a single structure; the decision about keeping them together or separated will be taken in the future depending on mechanical and integration considerations. The preliminary design choices adopted while designing these subsystems are presented considering the actual mechanical and thermal requirements. Particular attention is given to the derotation system design (K-mirror) and the analyses done to choose the materials and the adhesives.