ELT dome and telescope: performance analysis overview

The Extremely Large Telescope (ELT) is the largest near- and mid- infrared telescope of the world. The performance check of the preliminary design of the ELT has been completed through a variety of analyses: structural static analysis (FEM), modal and harmonic analysis (FEM), seismic spectrum and transient analysis (FEM), wind analysis (CFD and Wind Tunnel Test), thermal analysis (FEM), vibration analysis (FEM + State Space model), Servo analysis for pointing and tracking (State Space model). A FEM model of the telescope has been created to analyze the telescope behavior against all the significant actions: gravity, wind, seism, thermal, manufacturing and alignment errors. The model includes the telescope pier and the pier foundations. A Wind Tunnel Test campaign has been carried out on a scaled model of the Dome and Telescope to assess the wind action on the structures. The campaign has been supported by a detailed CFD analysis with several cases of Dome orientation, Dome configuration, wind velocity and turbulence intensity. A State Space model of the telescope has been set up to perform the Servo analysis of the azimuth and altitude control system. A comprehensive State Space model of the Dome, the Ground, and the Main Structure has been set up to perform the vibration analysis of the whole observatory (including the machinery in the auxiliary building and the erratic vibrations from the ground). The present paper provides a synthetic description of the generated models and the most significant results.