GRAVITY: beam stabilization and light injection subsystems

O. Pfuhl; M. Haug; F. Eisenhauer; D. Penka; A. Amorim; S. Kellner; S. Gillessen; T. Ott; E. Wieprecht; E. Sturm; F. Haußmann; S. Huber; M. Lippa; L. Burtscher; K. Rousselet-Perraut; C. Straubmeier; G. Perrin; W. Brandner

doi:10.1117/12.925391

12 September 2012 GRAVITY: beam stabilization and light injection subsystems

O. Pfuhl, M. Haug, F. Eisenhauer, D. Penka, A. Amorim, S. Kellner, S. Gillessen, T. Ott, E. Wieprecht, E. Sturm, F. Haußmann, S. Huber, M. Lippa, L. Burtscher, K. Rousselet-Perraut, C. Straubmeier, G. Perrin, W. Brandner

Author Affiliations +

Proceedings Volume 8445, Optical and Infrared Interferometry III; 84451U (2012) https://doi.org/10.1117/12.925391
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

We present design results of the 2nd generation VLTI instrument GRAVITY beam stabilization and light injection subsystems. Designed to deliver micro-arcsecond astrometry, GRAVITY requires an unprecedented stability of the VLTI optical train. To meet the astrometric requirements, we have developed a dedicated 'laser guiding system', correcting the longitudinal and lateral pupil position as well as the image jitter. The actuators for the correction are provided by four 'fiber coupler' units located in the GRAVITY cryostat. Each fiber coupler picks the light of one telescope and stabilizes the beam. Furthermore each unit provides field de-rotation, polarization analysis as well as atmospheric piston correction. Using a novel roof-prism design offers the possibility of on-axis as well as off-axis fringe tracking without changing the optical train. Finally the stabilized beam is injected with minimized losses into singlemode fibers via parabolic mirrors. We present lab results of the first guiding- as well as the first fiber coupler prototype regarding the closed loop performance and the optical quality. Based on the lab results we discuss the on-sky performance of the system and the implications concerning the sensitivity of GRAVITY.

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O. Pfuhl, M. Haug, F. Eisenhauer, D. Penka, A. Amorim, S. Kellner, S. Gillessen, T. Ott, E. Wieprecht, E. Sturm, F. Haußmann, S. Huber, M. Lippa, L. Burtscher, K. Rousselet-Perraut, C. Straubmeier, G. Perrin, and W. Brandner "GRAVITY: beam stabilization and light injection subsystems", Proc. SPIE 8445, Optical and Infrared Interferometry III, 84451U (12 September 2012); https://doi.org/10.1117/12.925391

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