Journal ArticleDOI
Optical Turbulence Profiles at Mauna Kea Measured by MASS and SCIDAR
TLDR
The vertical distribution of turbulence over Mauna Kea has been measured on four nights in 2002 October, simultaneously using two different instruments based on stellar scintillation, the generalized SCIDAR (scintillation detection and ranging) and MASS (multi-aperture scINTillation sensor) as discussed by the authors.Abstract:
The vertical distribution of turbulence over Mauna Kea has been measured on four nights in 2002 October, simultaneously using two different instruments based on stellar scintillation—the generalized SCIDAR (scintillation detection and ranging) and MASS (multiaperture scintillation sensor). The turbulence integrals match within 20%, and the low-resolution profiles delivered by MASS correctly reveal the localization of the strongest high-altitude turbulent layers. As deduced from DIMM (differential image motion monitor), MASS, and SCIDAR measurements, optical turbulence in the first 0.7 km above the summit contributed typically half of the total integral, the latter corresponding to a seeing of 0 .5. The ground layer and free atmosphere are not correlated.read more
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Proceedings ArticleDOI
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVIII
Abstract: The Kepler spacecraft launched on March 7, 2009, initiating NASA’s first search for Earth-size planets orbiting Sun-like stars. Since launch, Kepler has announced the discovery of 17 exoplanets, including a system of six transiting a Sun-like star, Kepler-11, and the first confirmed rocky planet, Kepler-10b, with a radius of 1.4 that of Earth. Kepler is proving to be a cornucopia of discoveries: it has identified over 1200 candidate planets based on the first 120 days of observations, including 54 that are in or near the habitable zone of their stars, and 68 that are 1.2 Earth radii or smaller. An astounding 408 of these planetary candidates are found in 170 multiple systems, demonstrating the compactness and flatness of planetary systems composed of small planets. Never before has there been a photometer capable of reaching a precision near 20 ppm in 6.5 hours and capable of conducting nearly continuous and uninterrupted observations for months to years. In addition to exoplanets, Kepler is providing a wealth of astrophysics, and is revolutionizing the field of asteroseismology. Designing and building the Kepler photometer and the software systems that process and analyze the resulting data to make the discoveries presented a daunting set of challenges, including how to manage the large data volume. The challenges continue into flight operations, as the photometer is sensitive to its thermal environment, complicating the task of detecting 84 ppm drops in brightness corresponding to Earth-size planets transiting Sun-like stars.
Journal ArticleDOI
Limits of adaptive optics for high-contrast imaging
TL;DR: In this paper, the effects of photon noise, aliasing, wave front chromaticity, and scintillation on the point-spread function (PSF) contrast achievable with ground-based adaptive optics (AO) are evaluated for different wave front sensing schemes.
Journal ArticleDOI
The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Performance Characterization
Marcos A. van Dam,Antonin Bouchez,David Le Mignant,Erik M. Johansson,Peter Wizinowich,Randy Campbell,Jason C. Y. Chin,S. K. Hartman,R. Lafon,Paul J. Stomski,Douglas M. Summers +10 more
TL;DR: The first 8-10 m class telescope equipped with a laser guide star adaptive optics (LGS AO) system is the Keck II Telescope as mentioned in this paper, which produces K-band Strehl ratios between 30% and 40% using bright tip-tilt guide stars.
Journal ArticleDOI
Combined MASS-DIMM instruments for atmospheric turbulence studies
V. G. Kornilov,Andrei Tokovinin,N. I. Shatsky,Olga Voziakova,Sergey A. Potanin,Boris Safonov +5 more
TL;DR: In this paper, a short recall of measured quantities and operational principles, the optics and elec- tronics of MASS-DIMM, interfacing to telescopes and detectors, and operation are covered in some detail.
Journal ArticleDOI
Accurate seeing measurements with MASS and DIMM
Andrei Tokovinin,V. G. Kornilov +1 more
TL;DR: In this article, a modified version of the multi-aperture scintillation sensor (MASS) was developed to compensate for partially saturated scintillated data, which can reach an accuracy of ∼ 10 per cent when their biases are carefully controlled.
References
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Journal ArticleDOI
Adaptive Optics in Astronomy
Francois Roddier,Laird Thompson +1 more
TL;DR: An approach to design electro‐optical systems that measure and undo the effects of clear‐air turbulence in real time, delivering near‐diffraction‐limited performance at infrared and visible wavelengths at optical wavelengths.
Journal ArticleDOI
Exceptional astronomical seeing conditions above Dome C in Antarctica
TL;DR: Observations of the wintertime seeing from Dome C, a high point on the Antarctic plateau at a latitude of 75° S, are reported, and the results are remarkable: the median seeing is 0.27 arcsec, and below 0.15arcsec 25 per cent of the time.
Journal ArticleDOI
From Differential Image Motion to Seeing
TL;DR: The theory of the differential image motion monitor (DIMM) is reviewed and extended in this paper. But the contribution of CCD readout noise to image motion variance is modeled, and it can substantially bias DIMM results if left unsubtracted.