Print Email Facebook Twitter Dynamic testing of primary mirror segment supports for the Extremely Large Telescope Title Dynamic testing of primary mirror segment supports for the Extremely Large Telescope Author Witvoet, G. Nijenhuis, J.R. Kramer, L. Contributor Marshall, H.K. (editor) Spyromilio, J. (editor) Publication year 2018 Abstract The preparations for the design and construction of the Extremely Large Telescope (ELT) are in full swing. One of the most critical components of this enormous telescope is its segmented primary mirror (M1), for which Netherlands Organisation for Applied Scientific Research (TNO), in collaboration with VDL, has designed the mechanical segment support (M1SS) in the period 2015-2016.1 This new M1SS design is based on the previous M1SS prototypes developed in 2009-2010,2 but includes several enhancements to further improve its performance. Specific design drivers were, among others, the serviceability of the M1SS, the introduced surface form error at the segment, and the increased target values for the structural eigenfrequencies. The latter defines the dynamic performance of the structure (including the ∼178 kg segment), which needed to be validated experimentally. From the latest M1SS design one engineering model (EM) and six qualification models (QMs) have been manufactured recently, which have tested intensively to verify their performance. This work will present the test procedure employed to validate the dynamic behavior, describe these dynamic tests and present their results in detail. During these tests a QM, including a dummy segment, has been placed on a heavy rigid structure and three accelerometers have been mounted across the assembly. The structure has then been excited on several strategic locations using a roving hammer technique,3 resulting in a large collection of frequency responses. From these, the eigenfrequencies and accompanying mode shapes have been estimated, resulting in accurate determination of the clocking, lateral, piston and tip/tilt modes of the structure. This allows for correct assessment of the dynamic performance and comparison to the design objectives and finite element model (FEM) predictions. This procedure has been applied to two different QMs, but since each M1SS consists of a fixed frame (FF) and a removable segment assembly (SA), four different configurations have been tested. The results demonstrate compliance with the challenging design objectives for all QMs, and they show only small variations among the configurations, demonstrating that the dynamic performance of the M1SS design is very reproducible. Subject High Tech Systems & MaterialsIndustrial InnovationELTSegment supportAirborne telescopesDynamic analysisFrequency responseMachine designMechanismsOptical telescopesOptical testingRigid structuresExtremely Large TelescopesPrimary mirror segmentsQualification modelScientific researchesSegmented primary mirrorsStrategic locationsStructural design To reference this document use: http://resolver.tudelft.nl/uuid:8a91dc1c-2fa8-4d43-b50b-bb5f35b4e386 TNO identifier 842190 Publisher SPIE ISBN 9781510619531 ISSN 0277-786X Source Ground-Based and Airborne Telescopes VII 2018, 10-15 June 2018, Austin, TX, USA, 10700 Series Proceedings of SPIE - The International Society for Optical Engineering Article number 107003J Document type conference paper Files To receive the publication files, please send an e-mail request to TNO Library.