22 August 2014 Extremely high-resolution ground-layer optical turbulence profile at Mauna Kea
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Abstract
We present high resolution optical turbulence profiles of the dome and ground-layers measured using a set of Shack- Hartmann wavefront sensors deployed over a field of view of between 0.5 and 1.0 degrees at the focal planes of the University of Hawaii 2.2-m telescope and the Canada-France-Hawaii Telescope on Maunakea, Hawaii. Observations with the experiment were made over the course of several nights on each telescope. We obtain estimates of the strength, distribution, and velocities of optical turbulence from the covariance matrices and maps of the measured wavefront gradients and a decomposition of the measured wavefronts into Zernike polynomials. We find agreement with previous measurements on Maunakea that the ground layer is largely confined within the first tens of meters above the ground and moves at the ground wind velocity. In addition, we spatially resolve the optical turbulence that arises from within the dome. For both facilities we find that the dome seeing is a major component of the overall turbulence strength accounting for more than half of the turbulence within the ground layer and that the dome seeing changes very slowly with a characteristic frequency of less than 1 Hz. While the variety of observing conditions sampled is low, we find that the characteristics of the dome seeing with observation elevation angle and the azimuth angle with respect to the ground wind are quite different on the two telescopes suggesting a different origin to the seeing within the two enclosures.
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Mark R. Chun, Mark R. Chun, Olivier Lai, Olivier Lai, Timothy Butterley, Timothy Butterley, Sean Goebel, Sean Goebel, Christoph Baranec, Christoph Baranec, Douglas Toomey, Douglas Toomey, } "Extremely high-resolution ground-layer optical turbulence profile at Mauna Kea", Proc. SPIE 9148, Adaptive Optics Systems IV, 914867 (22 August 2014); doi: 10.1117/12.2056864; https://doi.org/10.1117/12.2056864
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