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|Title:||The crystal ball, the spider and other stories: a journey around the test tower of the M4 adaptive mirror||Authors:||BRIGUGLIO PELLEGRINO, RUNA ANTONIO
|Issue Date:||2018||Volume:||Adaptive Optics Systems VI||Editors:||Close, Laird M.; Schreiber, Laura; Schmidt, Dirk||Series:||PROCEEDINGS OF SPIE||Number:||10703||First Page:||1070373||Abstract:||M4 is the adaptive mirror of ELT, currently at its FDR. It is composed by 6 thin shell mirror segments, controlled by 5136 voice coil actuators. Before its installation at the telescope, it will be optically calibrated on a test facility (OTT) in Italy. The calibration includes the computation of the flattening command and the segments co-phasing, i.e. the correction of the differential piston amongst them. Given the large complexity of the deformable mirror and the very tight requests on the measurement accuracy, we set-up a risk-mitigation activity based on the laboratory demonstration of some key elements within the test tower. In this paper we present the results of the experimentation. We measured at nanometer level the interferometric cavity; we investigated how the interferometer reacts in presence of spider arms dividing the test mirror into separated islands; we integrated and tested a multi wavelength sensor to measure the inter-segment absolute differential piston; we aligned and tested for stability the pupil relaying optical system to be installed on the OTT. Such activity is performed in the AO laboratory at INAF-Arcetri in Italy, in preparation of the M4 optical calibration on the OTT, scheduled to start in 2020. The M4 project is led by the Italian consortium AdOptica under an ESO contract.||Conference Name:||Adaptive Optics Systems VI||Conference Place:||Austin, Texas, United States||Conference Date:||10-15 June, 2018||URI:||http://hdl.handle.net/20.500.12386/30690||URL:||https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10703/2311334/The-crystal-ball-the-spider-and-other-stories--a/10.1117/12.2311334.short?SSO=1||ISSN:||0277-786X||ISBN:||9781510619593
|Appears in Collections:||3.01 Contributi in Atti di convegno|
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checked on Jun 15, 2021
checked on Jun 15, 2021
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