Universität zu Köln

Anugu, N., Amorim, A., Gordo, P., Eisenhauer, F., Pfuhl, O., Haug, M., Wieprecht, E., Wiezorrek, E., Lima, J., Perrin, G., Brandner, W., Straubmeier, C., Le Bouquin, J-B. and Garcia, P. J. V. (2018). Methods for multiple-telescope beam imaging and guiding in the near-infrared. Mon. Not. Roy. Astron. Soc., 476 (1). S. 459 - 470. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

Atmospheric turbulence and precise measurement of the astrometric baseline vector between any two telescopes are two major challenges in implementing phase-referenced interferometric astrometry and imaging. They limit the performance of a fibre-fed interferometer by degrading the instrument sensitivity and the precision of astrometric measurements and by introducing image reconstruction errors due to inaccurate phases. A multiple-beam acquisition and guiding camera was built to meet these challenges for a recently commissioned four-beam combiner instrument, GRAVITY, at the European Southern Observatory Very Large Telescope Interferometer. For each telescope beam, it measures (a) field tip-tilts by imaging stars in the sky, (b) telescope pupil shifts by imaging pupil reference laser beacons installed on each telescope using a 2x2 lenslet and (c) higher-order aberrations using a 9x9 Shack-Hartmann. The telescope pupils are imaged to provide visual monitoring while observing. These measurements enable active field and pupil guiding by actuating a train of tip-tilt mirrors placed in the pupil and field planes, respectively. The Shack-Hartmann measured quasi-static aberrations are used to focus the auxiliary telescopes and allow the possibility of correcting the non-common path errors between the adaptive optics systems of the unit telescopes and GRAVITY. The guiding stabilizes the light injection into single-mode fibres, increasing sensitivity and reducing the astrometric and image reconstruction errors. The beam guiding enables us to achieve an astrometric error of less than 50 mu as. Here, we report on the data reduction methods and laboratory tests of the multiple-beam acquisition and guiding camera and its performance on-sky.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Anugu, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Amorim, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gordo, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Eisenhauer, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pfuhl, O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Haug, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wieprecht, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wiezorrek, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lima, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Perrin, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Brandner, W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Straubmeier, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Le Bouquin, J-B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Garcia, P. J. V. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-188865
DOI:	10.1093/mnras/sty223
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	476
Number:	1
Page Range:	S. 459 - 470
Date:	2018
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language VLTI DELAY-LINES; INSTRUMENTS; REFRACTION; SYSTEM Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18886