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Proceedings Paper

Architecture of the metrology for the SRT
Author(s): Tonino Pisanu; Franco Buffa; Gian Luigi Deiana; Pasqualino Marongiu; Marco Morsiani; Claudio Pernechele; Sergio Poppi; Giampaolo Serra; Giampaolo Vargiu
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Paper Abstract

The Sardinia Radio Telescope (SRT) Metrology team is planning to install an initial group of devices on the new 64 meters radio-telescope. These devices will be devoted for the realization of the antenna deformation control system: an electronic inclinometer able to monitor the alidade deformations and a Position Sensing Device (PSD) able to map the antenna secondary mirror (M2) displacements and tilts. The inclinometer will be used to map the rail conditions, the azimuthal axis inclination and the thermal effects on the alidade structure. The PSD will be used to measure the secondary mirror displacements induced by the gravity and by the thermal deformations that produce shifts and tilts with respect to its ideal optical alignment. The PSD will be traced by diode laser installed on a mechanically stable position inside the elevation equipment room. The inclinometer has been tested in laboratory with the aim to compare its performances with a reference measurement system. The PSD and the laser have been characterized by a long-term tests to assess their stability and accuracy, thus simulating the open air conditions that will be experienced by the device during its operative life. M2 may move freely in space thanks to a six axis actuator system (hexapod). The PSD measurements are processed by a hexapod kinematic model (HKM) to evaluate the correct actuator elongations, thus closing the control loop. The sensors will be acquired and recorded by a dedicated PC installed in the Alidade equipment room and connected to the sensors via the Ethernet network.

Paper Details

Date Published: 17 September 2012
PDF: 9 pages
Proc. SPIE 8444, Ground-based and Airborne Telescopes IV, 84442E (17 September 2012); doi: 10.1117/12.925547
Show Author Affiliations
Tonino Pisanu, INAF - Osservatorio Astronomico di Cagliari (Italy)
Franco Buffa, INAF - Osservatorio Astronomico di Cagliari (Italy)
Gian Luigi Deiana, INAF - Osservatorio Astronomico di Cagliari (Italy)
Pasqualino Marongiu, INAF - Osservatorio Astronomico di Cagliari (Italy)
Marco Morsiani, INAF - Istituto di Radioastronomia (Italy)
Claudio Pernechele, INAF - Osservatorio Astronomico di Padova (Italy)
Sergio Poppi, INAF - Osservatorio Astronomico di Cagliari (Italy)
Giampaolo Serra, INAF - Osservatorio Astronomico di Cagliari (Italy)
Giampaolo Vargiu, INAF - Osservatorio Astronomico di Cagliari (Italy)

Published in SPIE Proceedings Vol. 8444:
Ground-based and Airborne Telescopes IV
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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