Keck Interferometer

Colavita, M. M.; Boden, Andrew F.; Crawford, S.; Meinel, A. B.; Shao, Michael; Swanson, Paul N.; Belle, G. T. van; Vasisht, Gautam; Walker, James M.; Wallace, J. Kent; Wizinowich, Peter

doi:10.1117/12.317145

Cited by 28 publications

(14 citation statements)

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“…Since ground-based monopupil telescopes were thought to be limited by atmospheric noise and therefore to have rather poor precision (Lindegren 1980), until now only high-precision optical interferometers such as SIM Paczyński 1998), Palomar Testbed Interferometer (Lane & Muterspagh 2004), Keck (Colavita et al 1998), and VLTI (Wittkowski et al 2004) were considered for carrying out observations with such precision. Recent progress in adaptive optics, and its application to astrometry (Pravdo et al 2005) opens new potentials for a dramatic improvement of the precision.…”

Section: Introductionmentioning

confidence: 99%

High-precision astrometry on the VLT/FORS1 at time scales of few days

Lazorenko

Mayor

Dominik

et al. 2007

A&A

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Aims. We investigate the accuracy of astrometric measurements with the VLT/FORS1 camera and consider potential applications. Methods. The study is based on two-epoch (2000 and 2002/2003) frame series of observations of a selected Galactic Bulge sky region that were obtained with FORS1 during four consecutive nights each. Reductions were carried out with a novel technique that eliminates atmospheric image motion and does not require a distinction between targets and reference objects. Results. The positional astrometric precision was found to be limited only by the accuracy of the determination of the star photocentre, which is typically 200-300 µas per single measurement for bright unsaturated stars B = 18−19. Several statistical tests showed that at time-scales of 1-4 nights the residual noise in measured positions is essentially a white noise with no systematic instrumental signature and no significant deviation from a Gaussian distribution. Some evidence of a good astrometric quality of the VLT for frames separated by two years was also found. Conclusions. Our data show that the VLT with FORS1/2 cameras can be effectively used for astrometric observations of planetary microlensing events and other applications where a high accuracy is required, that is expected to reach 30-40 µas for a series of 50 frames (one hour with R special filter).

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Section: Introductionmentioning

confidence: 99%

High-precision astrometry on the VLT/FORS1 at time scales of few days

Lazorenko

Mayor

Dominik

et al. 2007

A&A

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“…The main challenge of very high angular resolution is to drastically improve the limiting magnitude. Several SIs under construction plan to use large telescopes corrected by AO techniques, such as the VLTI (Donaldson et al 2000), the Keck Interferometer (Colavita et al 1998), and the GI2T (Mourard et al 1994), for which an AO system based on a curvature WFS and a BDM is under construction (Vérinaud et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Piston control with adaptive optics in stellar interferometry

Vérinaud

Cassaing

2001

A&A

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Abstract. The general purpose of an adaptive optics system is to correct for the wavefront corrugations due to atmospheric turbulence. When applied to a stellar interferometer, care must be taken in the control of the mean optical path length, commonly called differential piston. This paper defines a general formalism for the piston control of a deformable mirror in the linear regime. It is shown that the usual filtering of the piston mode in the command space is not sufficient, mostly in the case of a bimorph mirror. Another algorithm is proposed to cancel in the command space the piston produced in the pupil space. This analysis is confirmed by simulations in the case of the GI2T interferometer located on Plateau de Calern, France. The contrast of the interference fringes is severely reduced in the case of a classical wavefront correction, even in short exposures, but is negligible with our algorithm, assuming a realistic calibration of the mirror. For this purpose, a simple concept for the calibration of the piston induced by a deformable mirror is proposed.

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“…Optical interferometers are running routinely now, producing excellent science (Baldwin et al 1998;Mourard et al 1998;Traub 1998;Townes et al 1998;Johnston 1998;Wallace et al 1998;Davis et al 1998). Soon new object classes will become observable with interferometers which provide large apertures as VLTI and Keck Colavita et al 1998). Within the next ten years space borne interferometry will offer many advantages including the absence of atmospheric absorption and turbulence, and the possibility to achieve very long baselines (Shao 1998;Penny et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Modeling the imaging process in optical stellar interferometers

Schöller¹,

Wilhelm

Koehler³

2000

Astron. Astrophys. Suppl. Ser.

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Abstract. Optical interferometers on the ground, like ESO's Very Large Telescope Interferometer (VLTI) and the Keck Interferometer, and in space, like the InfraRed Space Interferometer (IRSI/Darwin) and the Space Interferometry Mission (SIM), will bring a major breakthrough in optical and near-infrared high angular resolution astronomy at the beginning of the next millennium. These instruments are complex systems with an exceptionally interdisciplinary character involving active/adaptive optics, structural mechanics, control engineering, electronics and various environmental disturbances (e.g. atmospheric turbulence and absorption, wind, seismic noise). For their design and development an approach from two sides is appropriate: laboratory testbeds are used for experimental investigations while numerical modeling tools perform an End-to-End instrument simulation. We have developed a set of numerical modeling tools to simulate the dynamic imaging process of an interferometer. The time-dependent point spread function (PSF) mainly characterizes the imaging performance of the instrument. It is computed by an optomechanical model. Based on the knowledge of the PSF the image of an incoherently radiating extended object is computed using a Fourier optical method. This article describes the modeling approach including an extension to more than two interferometric beams. Some results of simulations on the VLTI as a representative example are shown.

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Keck Interferometer

Cited by 28 publications

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High-precision astrometry on the VLT/FORS1 at time scales of few days

High-precision astrometry on the VLT/FORS1 at time scales of few days

Piston control with adaptive optics in stellar interferometry

Modeling the imaging process in optical stellar interferometers

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