In order to achieve a resolving power of ~20000, CUBES requires a fairly large beam diameter (160 mm). Consequently, the instrument envelope is becoming fairly large compared to other Cassegrain instruments (e.g., X-Shooter with 100 mm). Scaling classical instrument designs to the required size of CUBES would result in exceeding the mass limit of 2500 kg for UT Cassegrain instruments. Therefore, the mechanical design of CUBES needs to adopt light-weight construction principles and makes use of modern composite materials.
In the current design, CUBES main mechanical structure is divided into three main components:
a telescope adapter, that provides a stiff connection between the Cassegrain telescope flange and the optical bench assembly of CUBES
an optical bench assembly, that provides a stable platform for the spectrograph optics as well as for the fore optics
a support frame assembly to provide support for auxiliary equipment of CUBES such as electronic racks, the calibration unit and vacuum equipment. This frame is detached from the optical bench assembly in order to mitigate flexure contribution from auxiliary equipment.