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Proceedings Paper

The Fiber Coupler subsystem of the future VLTI instrument GRAVITY
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Paper Abstract

We present the Fiber Coupler subsystem of the future VLTI instrument GRAVITY. GRAVITY is specifically designed to deliver micro-arcsecond astrometry and deep interferometric imaging. The Fiber Coupler is designed to feed the light from a science and a reference object into single-mode fibers. The Fiber Coupler consists of four independent units. The units de-rotate the FoV. A motorized half-wave plate allows rotating the liner polarization axis. Each unit provides actuators for fast piston actuation, tip-tilt correction and pupil stabilization for one of the beams from four VLT telescopes. The actuators are operated in closed-loop. Together with a dedicated Laser Guiding System, this allows to stabilize the beams and maximize the coherently coupled light. The fast piston actuator provides the crucial fringe tracking capability at a bandwidth of >220Hz. A special roof prism design allows to either split the FoV or to serve as a 50/50 beam splitter without changing the optical path. This offers the possibility of on-axis as well as off-axis fringe tracking. The optical train consists solely of mirrors, which ensures an achromatic behavior and maximum throughput. The sophisticated optical design compensates for aberrations which are introduced by off-axis parabolic mirrors. This allows to achieve Strehl ratios of >95% across the FoV.

Paper Details

Date Published: 22 July 2010
PDF: 8 pages
Proc. SPIE 7734, Optical and Infrared Interferometry II, 77342A (22 July 2010); doi: 10.1117/12.857506
Show Author Affiliations
O. Pfuhl, Max-Planck-Institut für extraterrestrische Physik (Germany)
F. Eisenhauer, Max-Planck-Institut für extraterrestrische Physik (Germany)
M. Haug, Max-Planck-Institut für extraterrestrische Physik (Germany)
M. Thiel, Max-Planck-Institut für extraterrestrische Physik (Germany)
S. Kellner, Max-Planck-Institut für extraterrestrische Physik (Germany)
A. Amorim, SIM, Fac. de Ciências da Univ. de Lisboa (Portugal)
W. Brandner, Max-Planck-Institut für Astronomie (Germany)
J. P. Berger, Lab. d'Astrophysique Observatoire de Grenoble (France)
European Southern Observatory (Germany)
K. Rousselet-Perraut, Laboratoire d'Astrophysique Obs. de Grenoble (France)
G. S. Perrin, LESIA, Observatoire de Paris Meudon (France)
Groupement d'Intérêt Scientifique PHASE (France)
C. Straubmeier, Univ. zu Köln (Germany)
S. Gillessen, Max-Planck-Institut für extraterrestrische Physik (Germany)
H. Bartko, Max-Planck-Institut für extraterrestrische Physik (Germany)
A. P. Gräter, Max-Planck-Institut für extraterrestrische Physik (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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