Fringe detection laser metrology for differential astrometric stellar interferometers

S. Rabien; S. Gillessen; J. Ziegleder; Markus Thiel; Alex Gräter; Marcus Haug; F. Eisenhauer; Guy Perrin; Wolfgang Brandner; Christian Straubmeier

doi:10.1117/12.788099

28 July 2008 Fringe detection laser metrology for differential astrometric stellar interferometers

S. Rabien, S. Gillessen, J. Ziegleder, Markus Thiel, Alex Gräter, Marcus Haug, F. Eisenhauer, Guy Perrin, Wolfgang Brandner, Christian Straubmeier

Author Affiliations +

Proceedings Volume 7013, Optical and Infrared Interferometry; 70130I (2008) https://doi.org/10.1117/12.788099
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

Differential measurements with dual feed stellar interferometers using large baselines can deliver extremely accurate astrometric data. Separating the phase difference measured on the stars from the path length differences occurring within the interferometric instrument itself requires the use of laser interferometers. Usually heterodyne differential path techniques are used for nanometer precision measurements. With these methods it is usually difficult to track the full beam size and follow the light path up to the secondary mirror. We will report on the concept and first tests of a differential path metrology system, developed within the GRAVITY project, that allows one to measure the instrumental differential path over the full pupil size and up to the entrance pupil location. The differential phase is measured by detecting the laser fringe pattern created on the telescopes' secondaries. This novel method is almost free from systematic errors since the stellar and laser light are traveling along a common optical path.

Citation Download Citation

S. Rabien, S. Gillessen, J. Ziegleder, Markus Thiel, Alex Gräter, Marcus Haug, F. Eisenhauer, Guy Perrin, Wolfgang Brandner, and Christian Straubmeier "Fringe detection laser metrology for differential astrometric stellar interferometers", Proc. SPIE 7013, Optical and Infrared Interferometry, 70130I (28 July 2008); https://doi.org/10.1117/12.788099

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