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Proceedings Paper

First results from fringe tracking with the PRIMA fringe sensor unit
Author(s): J. Sahlmann; R. Abuter; S. Ménardi; C. Schmid; N. Di Lieto; F. Delplancke; R. Frahm; N. Gomes; P. Haguenauer; S. Lévêque; S. Morel; A. Mueller; T. Phan Duc; N. Schuhler; G. van Belle
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Paper Abstract

The fringe sensor unit (FSU) is the central element of the phase referenced imaging and micro-arcsecond astrometry (PRIMA) dual-feed facility for the Very Large Telescope interferometer (VLTI). It has been installed at the Paranal observatory in August 2008 and is undergoing commissioning and preparation for science operation. Commissioning observations began shortly after installation and first results include the demonstration of spatially encoded fringe sensing and the increase in VLTI limiting magnitude for fringe tracking. However, difficulties have been encountered because the FSU does not incorporate real-time photometric correction and its fringe encoding depends on polarisation. These factors affect the control signals, especially their linearity, and can disturb the tracking control loop. To account for this, additional calibration and characterisation efforts are required. We outline the instrument concept and give an overview of the commissioning results obtained so far. We describe the effects of photometric variations and beam-train polarisation on the instrument operation and propose possible solutions. Finally, we update on the current status in view of the start of astrometric science operation with PRIMA.

Paper Details

Date Published: 22 July 2010
PDF: 12 pages
Proc. SPIE 7734, Optical and Infrared Interferometry II, 773422 (22 July 2010); doi: 10.1117/12.856896
Show Author Affiliations
J. Sahlmann, Observatoire de Genève (Switzerland)
European Southern Observatory (Germany)
European Southern Observatory (Chile)
R. Abuter, European Southern Observatory (Germany)
S. Ménardi, European Southern Observatory (Germany)
C. Schmid, European Southern Observatory (Germany)
N. Di Lieto, European Southern Observatory (Germany)
F. Delplancke, European Southern Observatory (Germany)
R. Frahm, European Southern Observatory (Germany)
N. Gomes, European Southern Observatory (Germany)
P. Haguenauer, European Southern Observatory (Chile)
S. Lévêque, European Southern Observatory (Germany)
S. Morel, European Southern Observatory (Chile)
A. Mueller, European Southern Observatory (Germany)
Max-Planck-Institut fur Astronomie (Germany)
T. Phan Duc, European Southern Observatory (Germany)
N. Schuhler, European Southern Observatory (Chile)
G. van Belle, European Southern Observatory (Germany)

Published in SPIE Proceedings Vol. 7734:
Optical and Infrared Interferometry II
William C. Danchi; Françoise Delplancke; Jayadev K. Rajagopal, Editor(s)

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