The Very Large Telescope Interferometer v2012+

Haguenauer, Pierre; Abuter, R.; Andolfato, Luigi; Alonso, Jaime; Blanchard, Guillaume; Berger, J.‐P.; Bourget, P.; Brillant, S.; Dérie, F.; Delplancke, F.; Lieto, Nicola Di; Dupuy, Christophe; Gilli, Bruno; Gitton, Philippe B.; González, Juan Carlos; Guisard, Stéphane; Guniat, Serge; Hudepohl, Gerhard; Kaufer, A.; Lévêque, S.; Ménardi, Serge; Mérand, A.; Morel, S.; Percheron, Isabelle; Duc, Than Phan; Poupar, Sébastien; Ramírez, Andrés; Reineiro, Claudio; Sridharan, R.; Rivinius, Thomas; Schöller, M.; Schmid, Christian; Segovia, A.; Schuhler, Nicolas; Valdes, G.; Wit, W. J. de; Wittkowski, M.

doi:10.1117/12.925323

Cited by 12 publications

(2 citation statements)

References 4 publications

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“…GRAVITY 1 is an adaptive optics-assisted, near-infrared fringe-tracking beam combiner instrument for a set of four telescopes from the VLTI 2 . During a typical observation, GRAVITY will provide simultaneous interferometry of two objects within the 2'' field of view of the VLTI.…”

Section: Introductionmentioning

confidence: 99%

GRAVITY: metrology

Gillessen

Lippa

Eisenhauer

et al. 2012

Optical and Infrared Interferometry III

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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.

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Section: Introductionmentioning

confidence: 99%

GRAVITY: metrology

Gillessen

Lippa

Eisenhauer

et al. 2012

Optical and Infrared Interferometry III

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“…This study contains an extensive amount of data from the Very Large Telescope Interferometer (VLTI) facility of ESO (European Southern Observatory) in Paranal, Chile (Haguenauer et al, 2012). VLTI interferometri telecopes array can be set with utility telescopes (UTs, 8.2 m), or with the auxiliary telescopes (ATs, 1.8 m).…”

Section: The Vlti Amber and Pionier Interferometeric Beam-combinersmentioning

confidence: 99%

An interferometric view of hot star disks

Faes¹

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Comparison of fringe-tracking algorithms for single-mode near-infrared long-baseline interferometers

Choquet

Perrin

et al. 2014

A&A

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To enable optical long baseline interferometry toward faint objects, long integrations are necessary despite atmospheric turbulence. Fringe trackers are needed to stabilize the fringes and thus increase the fringe visibility and phase signal-to-noise ratio (S/N), with efficient controllers robust to instrumental vibrations and to subsequent path fluctuations and flux drop-outs. We report on simulations, analysis, and comparison of the performances of a classical integrator controller and of a Kalman controller, both optimized to track fringes under realistic observing conditions for different source magnitudes, disturbance conditions, and sampling frequencies. The key parameters of our simulations (instrument photometric performance, detection noise, turbulence, and vibrations statistics) are based on typical observing conditions at the Very Large Telescope observatory and on the design of the GRAVITY instrument, a 4-telescope single-mode long-baseline interferometer in the near-infrared, next in line to be installed at VLT Interferometer. We find that both controller performances follow a two-regime law with the star magnitude, a constant disturbance limited regime, and a diverging regime limited by both the detector and photon-noise. Moreover, we find that the Kalman controller is optimal in the high and medium S/N regime owing to its predictive commands based on an accurate disturbance model. In the low S/N regime, the model is not accurate enough to be more robust than an integrator controller. Identifying the disturbances from high S/N measurements improves the Kalman performances in the case of strong optical path difference disturbances.

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The Very Large Telescope Interferometer v2012+

Cited by 12 publications

References 4 publications

GRAVITY: metrology

GRAVITY: metrology

An interferometric view of hot star disks

Comparison of fringe-tracking algorithms for single-mode near-infrared long-baseline interferometers

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