AMOS has recently completed the on-site erection and performance evaluation campaign of the 2.5m telescope that is installed on Mount Abu (India) for the Physical Research Laboratory. The 20-m-focal-length telescope has a Ritchey-Chrétien optical configuration. It is equipped with a primary active mirror; an active positioning of the secondary mirror and a first order adaptive optical system. It operates in the 0.37-4 μm spectral range. The project fulfillment relies on the AMOS multidisciplinary expertise in design; manufacturing and verification of high-accuracy optical; mechanical and opto-mechanical systems. This paper presents the assembly; integration; alignment and verifications carried out on site. The alignment relies on the coma-free point method. The end-to-end telescope performances (image quality; pointing; tracking) are measured on sky using the verification instrument in combination with wavefront-curvature sensing and lucky imaging techniques.
The Extremely Large Telescope (ELT) is the largest optical and infrared telescope being planned and constructed at the present time. Its resolution overtakes current limits of performance for large telescopes, as well as current levels for all the engineering fields involved in the design and realization of the telescope. The design of the ELT Main Structure (MS) is supported by exhaustive performance and resistance analyses, which have now largely been completed. A Finite Element Model (FEM) of the MS has been created to analyse the telescope behaviour against all the significant actions, among which gravity, wind, seism, thermal, manufacturing and alignment tolerances can be mentioned. The model is characterized by several millions of degrees of freedom and it includes the Telescope pier and foundation, as well as the seismic isolation system and the natural soil. A detailed Computational Fluid Dynamic (CFD) model has been produced and validated with the support of a wind tunnel test campaign. Several cases of telescope orientation and Altitude configuration, wind velocities and turbulence intensities have been analysed. A State Space model has been set-up to perform the Servo analysis of the Azimuth and Altitude axes. Frictions and motor disturbances, encoders quantization, loops sampling and latencies have been considered, to assess tracking, slewing and offsetting performances and to assess the structural behaviour and the wind rejection. Finally, a comprehensive mathematical model of Dome, MS and soil has been set-up to perform the vibration analysis of the whole observatory. The purpose of this paper is to provide an overview of the generated models, the performed analyses and the most significant obtained results.
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