ASTRA: astrometry and phase-referencing astronomy on the Keck interferometer

Woillez, J.; Akeson, Rachel; Colavita, M. M.; Eisner, J. A.; Ghez, A. M.; Graham, James R.; Hillenbrand, Lynne A.; Millan-Gabet, R.; Monnier, John D.; Pott, Jörg-Uwe; Ragland, Sam; Wizinowich, Peter; Appleby, E.; Berkey, B.; Cooper, Andrew; Felizardo, C.; Herstein, J.; Hrynevych, M.; Martin, Olivier; Medeiros, D.; Morrison, D. R. O.; Panteleeva, T.; Smith, B. A.; Summers, K.; Tsubota, K.; Tyau, C.; Wetherell, Edward

doi:10.1117/12.857740

Cited by 22 publications

(16 citation statements)

References 10 publications

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“…• Two LGS AO systems pointing at the same interferometry target to support the ASTRA mode. 15 This scenario may require more personnel for operating the laser, but similar safety hardware and staffing for aircraft safety. The laser safety system may need to be modified to account for simultaneous shuttering of the two beams, and traffic control.…”

Section: Integration and Operation Transition For Keck I Lgs Ao And Dmentioning

confidence: 99%

AO operations at the W. M. Keck Observatory

Campbell

Mignant

Dam

et al. 2008

Observatory Operations: Strategies, Processes, and Systems II

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Natural Guide Star (NGS) and Laser Guide Star (LGS) Adaptive Optics (AO) have been offered for routine science operations to the W. M. Keck Observatory community since 2000 and late 2004, respectively. The AO operations team is now supporting ~100 nights of AO observing with four different instruments, including over fifty nights of LGS AO per semester. In this paper we describe improvements to AO operations to handle the large number of nights and to accommodate the recent upgrade to the wavefront sensor and wavefront controller. We report on the observing efficiency, image quality, scientific productivity, impact analysis from satellite safety procedures and discuss the support load required to operate AO at Keck. We conclude the paper by presenting our plans for dual LGS AO operations with Keck I -Keck II LGS, starting in 2009.

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Section: Integration and Operation Transition For Keck I Lgs Ao And Dmentioning

confidence: 99%

AO operations at the W. M. Keck Observatory

Campbell

Mignant

Dam

et al. 2008

Observatory Operations: Strategies, Processes, and Systems II

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“…At K band, the stars can be as far as ∼30 ′′ apart for true phase referencing. This approach is being attempted at the VLT (PRIMA, Delplancke et al 2006) and Keck Interferometers (ASTRA, Woillez et al 2010). This technique can be applied to only a small fraction of objects owing to the low sky density of bright phase reference calibrators.…”

Section: Visible and Infrared Sensitivitymentioning

confidence: 99%

Radio and Optical Interferometry: Basic Observing Techniques and Data Analysis

Monnier

Allen

2013

Planets, Stars and Stellar Systems

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Astronomers usually need the highest angular resolution possible when observing celestial objects, but the blurring effect of diffraction imposes a fundamental limit on the image quality from any single telescope. Interferometry allows light collected at widely-separated telescopes to be combined in order to synthesize an aperture much larger than an individual telescope thereby improving angular resolution by orders of magnitude. Because diffraction has the largest effect for long wavelengths, radio and millimeter wave astronomers depend on interferometry to achieve image quality on par with conventional large-aperture visible and infrared telescopes. Interferometers at visible and infrared wavelengths extend angular resolution below the milli-arcsecond level to open up unique research areas in imaging stellar surfaces and circumstellar environments.In this chapter the basic principles of interferometry are reviewed with an emphasis on the common features for radio and optical observing. While many techniques are common to interferometers of all wavelengths, crucial differences are identified that will help new practitioners to avoid unnecessary confusion and common pitfalls. The concepts essential for writing observing proposals and for planning observations are described, depending on the science wavelength, the angular resolution, and the field of view required. Atmospheric and ionospheric turbulence degrades the longest-baseline observations by significantly reducing the stability of interference fringes. Such instabilities represent a persistent challenge, and the basic techniques of phase-referencing and phase closure have been developed to deal with them. Synthesis imaging with large observing datasets has become a routine and straightforward process at radio observatories, but remains challenging for optical facilities. In this context the commonly-used image reconstruction algorithms CLEAN and MEM are presented. Lastly, a concise overview of current facilities is included as an appendix.

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“…2 and 3, this conference, for an operations and science update. Under NSF funding, Keck Observatory is continuing development of its ASTRA (ASTrometric and phase-Referenced Astronomy) project 9 to add additional capability to KI. ASTRA's selfphase-referenced high-spectral-resolution mode is currently available to the Keck community, the dual-field mode is entering the shared-risk observing phase, and the astrometric mode is under development.…”

Section: Introductionmentioning

confidence: 99%

Keck Interferometer nuller instrument performance

et al. 2010

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The Keck Interferometer combines the two 10 m Keck telescopes as a long baseline interferometer. It is funded by NASA as a joint development among the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the NASA Exoplanet Science Institute. In February 2008, the 10 um nulling mode began a 32 night observing program with three key science teams to perform a survey of nearby stars for exozodiacal dust. This program has recently concluded, and has been followed by nuller observing on a variety of science topics through the standard proposal process. We provide a review and update of the nuller implementation, and describe the data reduction process, including the calibration approach. We then review the technical performance of the instrument based on the full key science data set, including sensitivity and systematic errors. We also provide some summary data on atmospheric effects applicable to the cophasing approach.

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ASTRA: astrometry and phase-referencing astronomy on the Keck interferometer

Cited by 22 publications

References 10 publications

AO operations at the W. M. Keck Observatory

AO operations at the W. M. Keck Observatory

Radio and Optical Interferometry: Basic Observing Techniques and Data Analysis

Keck Interferometer nuller instrument performance

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