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Proceedings Paper

GRAVITY: metrology
Author(s): Stefan Gillessen; Magdalena Lippa; Frank Eisenhauer; Oliver Pfuhl; Marcus Haug; Stefan Kellner; Thomas Ott; Ekkehard Wieprecht; Eckhard Sturm; Frank Haußmann; Clemens F. Kister; David Moch; Markus Thiel
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Paper Abstract

GRAVITY is a second generation VLTI instrument, combining the light of four telescopes and two objects simultaneously. The main goal is to obtain astrometrically accurate information. Besides correctly measured stellar phases this requires the knowledge of the instrumental differential phase, which has to be measured optically during the astronomical observations. This is the purpose of a dedicated metrology system. The GRAVITY metrology covers the full optical path, from the beam combiners up to the reference points in the beam of the primary telescope mirror, minimizing the systematic uncertainties and providing a proper baseline in astrometric terms. Two laser beams with a fixed phase relation travel backward the whole optical chain, creating a fringe pattern in any plane close to a pupil. By temporal encoding the phase information can be extracted at any point by means of flux measurements with photo diodes. The reference points chosen sample the pupil at typical radii, eliminating potential systematics due differential focus. We present the final design and the performance estimate, which is in accordance with the overall requirements for GRAVITY.

Paper Details

Date Published: 12 September 2012
PDF: 9 pages
Proc. SPIE 8445, Optical and Infrared Interferometry III, 84451O (12 September 2012); doi: 10.1117/12.926813
Show Author Affiliations
Stefan Gillessen, Max-Planck-Institute for extraterrestrial Physics (Germany)
Magdalena Lippa, Max-Planck-Institute for extraterrestrial Physics (Germany)
Frank Eisenhauer, Max-Planck-Institute for extraterrestrial Physics (Germany)
Oliver Pfuhl, Max-Planck-Institute for extraterrestrial Physics (Germany)
Marcus Haug, Max-Planck-Institute for extraterrestrial Physics (Germany)
Stefan Kellner, Max-Planck-Institute for extraterrestrial Physics (Germany)
Thomas Ott, Max-Planck-Institute for extraterrestrial Physics (Germany)
Ekkehard Wieprecht, Max-Planck-Institute for extraterrestrial Physics (Germany)
Eckhard Sturm, Max-Planck-Institute for extraterrestrial Physics (Germany)
Frank Haußmann, Max-Planck-Institute for extraterrestrial Physics (Germany)
Clemens F. Kister, Max-Planck-Institute for extraterrestrial Physics (Germany)
David Moch, Max-Planck-Institute for extraterrestrial Physics (Germany)
Markus Thiel, Max-Planck-Institute for extraterrestrial Physics (Germany)


Published in SPIE Proceedings Vol. 8445:
Optical and Infrared Interferometry III
Françoise Delplancke; Jayadev K. Rajagopal; Fabien Malbet, Editor(s)

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