The Mid-infrared ELT Imager and Spectrograph (METIS) is one of the first-light scientific instruments for the ELT with over 75 optical components. The science cases of METIS impose tight stability requirements on the optical performance. To assess whether the optical performance is harmed by micro-vibrations, the effect of numerous vibration sources on the optical stability are analyzed. We present the analysis approach and results for METIS. This includes finite element analysis to obtain transfer functions, compute rigid body motion response of optical elements and assess the optical impact by ray-tracing.
For the ELT, a total of 931 M1 Segment Assemblies will be manufactured. These will be of 133 different types, 7 copies each, with different optical and mechanical properties. The manufacturing of the segment support, the glass blank and the polishing will be done by industrial partners. ESO will be responsible for the shipment of the Segment Assemblies to Chile, for the integration of the edge sensors and their electronics, and for the cleaning and coating. After performing several health- and quality-checks, the Segment Assemblies will be temporarily stored in the warehouse, before being installed at the telescope and eventually recoated around every 2 years. The telescopes and instruments for optical astronomy are usually prototypes, while a new approach is required to manage such a series production of crucial components, which differ in small but significant aspects. In this paper, we will present the processes we have developed to manage the series production of M1 Segment Assemblies for the ELT, starting from the reception of the Segment Assemblies in Chile, inspection, installation of sub-components, health-checks, storage, and installation at the telescope.
ESO took a systematic approach at earliest phases of the ELT programme to address different aspects of vibration at the telescope, from modelling, error budgeting, requirement specifications, to envisaging verification and mitigation methods. Recent activities focused on measuring and characterizing the vibrational forces generated by typical equipment in the observatory. In addition, the measurements are performed to design and verify the efficiency of the required isolation systems. In this paper, a complete system analysis using these measurement data as input to the detailed model of the telescope structure combined with hosted units, i.e. mirrors, instruments and other equipment, (all at final design phase) is presented. The analysis serves as a verifying tool to observe the actual state of the performance versus the top-level budget. It is also discussed how the results are used for improving the design and envisaging the potential mitigation strategies.
ESO took a systematic approach at earliest phases of the ELT programme to address different aspects of vibration at telescope, from modelling, error budgeting, requirement specifications, to envisaging verification and mitigation methods. Recent activities focused on characterisation of the vibrational forces generated by typical equipment in the observatory. Those measured forces combined with the models of the telescope are used to verify various subsystems specification as well as to verify the overall system performance. In this paper, an approach used for vibration force measurements together with some examples of the characterised sources are discussed. The verification of performance/requirements at telescope system/subsystem is performed using these measured data.
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