WST, the Wide-field Spectroscopic Telescope: Mechanical Design and FE Analyses for the High Resolution Spectrograph

Abstract

The Wide-field Spectroscopic Telescope (WST) is a planned 12-meter-class dedicated spectroscopic facility designed to address key scientific challenges through large spectroscopic surveys. This paper presents the current status of Work Package 4.5, which focuses on the High-Resolution Multi-Object Spectrograph (MOS-HR) module for WST. The MOSHR instrument is expected to provide a resolving power of R = 40,000 with a multiplexing capability of about 2,000 targets. The mechanical design activities carried out for the development of the HR spectrograph and for the definition of its optomechanical architecture are described. To account for both the scientific requirements of the spectrograph and the manufacturability constraints associated with such a complex instrument, the mechanical layout has been organized into four larger modules, each containing two sub-modules. Guided by feasibility considerations, such as mechanical performance, available volume, and fabrication and assembly aspects, each sub-module adopts a vertical optical bench configuration with optical elements mounted on both sides. Starting from the baseline optical design, the mechanical configuration has been developed to achieve the required alignment accuracy, structural stability, and environmental robustness. The workflow includes the translation of the optical prescription into a complete mechanical model, the definition of the main mounting and alignment interfaces, and preliminary static, modal, and seismic analyses to evaluate performance under operational and survival loads. As an outcome, the proposed design provides architecture that enables preliminary estimates of mass, volume, cost, and mechanical performance in terms of deformation, stress, and modal behavior of the modules.