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6b5b69e1146b1a48bf7d76b61efe495d.ppt
- Количество слайдов: 62
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Turbulence in earth’s atmosphere makes stars twinkle More importantly, turbulence spreads out light; makes it a blob rather than a point Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope! Page 5
Lick Observatory, 1 m telescope Long exposure image Short exposure image Image with adaptive optics Speckles (each is at diffraction limit of telescope) Page 6
Image is spread out into speckles Centroid jumps around (image motion) “Speckle images”: sequence of short snapshots of a star, taken at Lick Observatory using the IRCAL infra-red camera Page 7
stratosphere tropopause 10 -12 km wind flow over dome boundary layer ~ 1 km Heat sources w/in dome Page 8
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Point focus Parallel light rays blur Light rays affected by turbulence Page 10
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No adaptive optics With adaptive optics Note: “colors” (blue, red, yellow, white) indicate increasing intensity Page 15
Intensity Definition of “ trehl”: S Ratio of peak intensity to that of “perfect” optical system x Page 16
Lick Observatory No AO With AO Intensity With AO Page 17
Feedback loop: next cycle corrects the (small) errors of the last cycle Page 18
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BEFORE Incoming Wave with Aberration Deformable Mirror AFTER Corrected Wavefront Page 21
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Xinetics Page 24
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Keck Observatory Lick Observatory Page 27
Uncorrected image of a star Laser Guide Star correction Page 28
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} “Curvature sensing” systems > 210 journal articles on AO astronomy, to date Page 31
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DM Wavefront sensor Off-axis parabola mirror IRCAL infrared camera Page 33
Canada France Hawaii Telescope Fifteen minute integration time 0. 19 arc sec resolution
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200” telescope Page 37
Summit of Mauna Kea volcano in Hawaii: Subaru 2 Kecks Gemini North And at other places: MMT, VLT, LBT, Gemini South Page 38
Adaptive optics lives here Page 39
Nasmyth platform Person! Page 40
Without AO FWHM 0. 34 arc sec Strehl = 0. 6% With AO FWHM 0. 039 arc sec Strehl = 34% Page 41
2. 3 arc sec Without adaptive optics With Keck adaptive optics May 24, 1999 June 27, 1999 Page 42
Square root color map Linear color map H band (1. 65 microns) Page 43
Visible: Voyager 2 fly-by, 1989 Circumferential bands Compact southern features Compact features such as Great Dark Spot, smaller southern features: probably stable vortices Page 44
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