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11 July 2018 Deconstructing turbulence and optimizing GLAO using imaka telemetry
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Abstract
By analyzing global covariance matrices from the imaka GLAO system at the UH 2.2m telescope, it is possible to reconstruct ground layer strength, the integrated turbulence strength as well as the vertical turbulence profile. These are compared to simultaneous profiles obtained by the Maunakea facility MASS/DIMM. A method has been developed to directly compute the phase structure function from the covariances of the slopes, obtained from the telemetry data. The phase structure function allows to test the validity of the Kolmogorov (or van Karman) model and the spatial frequency content of the turbulence: Dome and telescope tube seeing are expected to have an excess of high spatial frequencies, which is detrimental to the PSF by amplifying the halo, and which the AO system cannot correct. The telescope, the dome and their interaction with the ground layer produce a complex environment for the turbulence. We are therefore developing a small, portable optical turbulence sensor which we will be able to use to scan the dome and telescope tube to quantify the local presence of turbulence. This is the AIR-FLOW (Airborne Interferometric Recombiner - Fluctuations of Light at Optical Wavelengths) project. With imaka and AIR-FLOW we hope to generate a coherent and quantitative account of the turbulence type and strength present in the telescope beam and to accurately match this detailed phase information to the focal plane images. Such a level of detail is required to understand and eventually be able to control the local environment for optimized image quality. We foresee this expertise will be especially valuable for ELTs, where the halo around the PSF will act like an extra source of background.
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Olivier Lai, Mark Chun, Fatima Abdurrahman, Jessica Lu, Max Service, Dora Fohring, and Doug Toomey "Deconstructing turbulence and optimizing GLAO using imaka telemetry", Proc. SPIE 10703, Adaptive Optics Systems VI, 107036D (11 July 2018); https://doi.org/10.1117/12.2313356
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