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Proceedings Paper

A PSD (position sensing device) to map the shift and tilt of the SRT secondary mirror
Author(s): Tonino Pisanu; Franco Buffa; Raimondo Concu; Pasqualino Marongiu; Mauro Pili; Sergio Poppi; Giampaolo Serra; Enrico Urru; Gianpaolo Vargiu
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Paper Abstract

The Sardinia Radio Telescope (SRT) Metrology team has started to install the 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 secondary mirror (M2) displacements and tilts. The inclinometer is 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 it s ideal optical alignment. The PSD will be traced by a laser diode installed on a mechanically stable position inside the vertex room. Preliminarly we decided to characterize excursion range of M2, in order to know if the PSD measuring range of about +/- 10 mm is enough for our purposes. We designed, built and tested an optical measuring device, based on commercial CMOS with a wider measurement range of +/- 40 mm and with a resolution of around 0.1 mm. After a laboratory characterization at the 23 meters real distance, the PSD and the laser have been installed in the antenna. In this paper we show the results of the measurements performed by moving the antenna in elevation.

Paper Details

Date Published: 22 July 2014
PDF: 9 pages
Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91454U (22 July 2014); doi: 10.1117/12.2055849
Show Author Affiliations
Tonino Pisanu, INAF - Osservatorio Astronomico di Cagliari (Italy)
Franco Buffa, INAF - Osservatorio Astronomico di Cagliari (Italy)
Raimondo Concu, INAF - Osservatorio Astronomico di Cagliari (Italy)
Pasqualino Marongiu, INAF - Osservatorio Astronomico di Cagliari (Italy)
Mauro Pili, INAF - Osservatorio Astronomico di Cagliari (Italy)
Sergio Poppi, INAF - Osservatorio Astronomico di Cagliari (Italy)
Giampaolo Serra, INAF - Osservatorio Astronomico di Cagliari (Italy)
Enrico Urru, INAF - Osservatorio Astronomico di Cagliari (Italy)
Gianpaolo Vargiu, INAF - Osservatorio Astronomico di Cagliari (Italy)

Published in SPIE Proceedings Vol. 9145:
Ground-based and Airborne Telescopes V
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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