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Proceedings Paper

GRAVITY: the impact of non-common optical paths within the metrology system
Author(s): Yitping Kok; Stefan Gillessen; Sylvestre Lacour; Frank Eisenhauer; Nicolas Blind; Johannes Weber; Magdalena Lippa; Oliver Pfuhl; Leonard Burtscher; Ekkehard Wieprecht; Thomas Ott; Marcus Haug; Stefan Kellner; Frank Haussmann; Eckhard Sturm; Annemieke Janssen; Reinhard Genzel; Guy Perrin; Karine Perraut; Christian Straubmeier; Wolfgang Brandner; Antonio Amorim; Oliver Hans
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Paper Abstract

The laser metrology system in the GRAVITY instrument plays a crucial role in an attempt at high-precision narrow-angle astrometry. With a design goal of achieving 10 microarcseconds precision in astrometry, the system must measure the optical path difference between two beam combiners within GRAVITY to an accuracy of better than 5nm. However in its current design, some parts of the optical paths of the metrology system are not common to the optical paths of starlight (the science path) which it must measure with high accuracy. This state of the design is true for most but not all the baselines which will be used by the GRAVITY instrument. The additional non-common optical paths could produce inaccurate path length measurements and consequently inaccurate measurements of the differential phase between fringe packets of two nearby celestial objects, which is the main astrometric observable of the instrument. With reference to the stability and the sensitivity of the non-common paths, this paper describes the impact of a biased differential phase measurement on the narrowangle astrometry and the image reconstruction performance of the GRAVITY instrument. Several alternative designs are also discussed.

Paper Details

Date Published: 24 July 2014
PDF: 17 pages
Proc. SPIE 9146, Optical and Infrared Interferometry IV, 914625 (24 July 2014); doi: 10.1117/12.2055567
Show Author Affiliations
Yitping Kok, Max-Planck-Institut für extraterrestrische Physik (Germany)
Stefan Gillessen, Max-Planck-Institut für extraterrestrische Physik (Germany)
Sylvestre Lacour, Lab. d'Etudes Spatiales et d'Instrumentation en Astrophysique, CNRS, Observatoire de Paris à Meudon (France)
Frank Eisenhauer, Max-Planck-Institut für extraterrestrische Physik (Germany)
Nicolas Blind, Max-Planck-Institut für extraterrestrische Physik (Germany)
Johannes Weber, Max-Planck-Institut für extraterrestrische Physik (Germany)
Magdalena Lippa, Max-Planck-Institut für extraterrestrische Physik (Germany)
Oliver Pfuhl, Max-Planck-Institut für extraterrestrische Physik (Germany)
Leonard Burtscher, Max-Planck-Institut für extraterrestrische Physik (Germany)
Ekkehard Wieprecht, Max-Planck-Institut für extraterrestrische Physik (Germany)
Thomas Ott, Max-Planck-Institut für extraterrestrische Physik (Germany)
Marcus Haug, Max-Planck-Institut für extraterrestrische Physik (Germany)
Stefan Kellner, Max-Planck-Institut für extraterrestrische Physik (Germany)
Frank Haussmann, Max-Planck-Institut für extraterrestrische Physik (Germany)
Eckhard Sturm, Max-Planck-Institut für extraterrestrische Physik (Germany)
Annemieke Janssen, Max-Planck-Institut für extraterrestrische Physik (Germany)
Reinhard Genzel, Max-Planck-Institut für extraterrestrische Physik (Germany)
Guy Perrin, Lab. d'Etudes Spatiales et d'Instrumentation en Astrophysique, CNRS, Observatoire de Paris à Meudon (France)
Karine Perraut, Univ. Grenoble Alpes (France)
Institut de Planétologie et d’Astrophysique de Grenoble (France)
Christian Straubmeier, Univ. zu Köln (Germany)
Wolfgang Brandner, Max-Planck-Institut für Astronomie (Germany)
Antonio Amorim, Fundacão da Faculdade de Ciências da Univ. de Lisboa (Portugal)
Oliver Hans, Max-Planck-Institut für extraterrestrische Physik (Germany)


Published in SPIE Proceedings Vol. 9146:
Optical and Infrared Interferometry IV
Jayadev K. Rajagopal; Michelle J. Creech-Eakman; Fabien Malbet, Editor(s)

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