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|Mauna Kea, Hawaii – February 5, 1999: The adaptive optics system on the Keck II telescope achieved first light tonight, with the closing of the AO loop and the successful sharpening of a stellar image. This|
brings adaptive optics capabilities to
the new generation of 10m-class telescopes
for the first time.
Fred Chaffee, director of the Keck Observatory, remarked that "This was an historic night at the Keck Observatory. The promise of producing diffraction-limited near-infrared images on the world's largest telescope reached a major milestone tonight, with the first closing of the AO loop. The AO team and the many others on the Observatory staff who made this evening possible deserve the heartiest congratulations. Scott Acton may have put it best at night's end: 'It's a miracle!' "
Adaptive optics refers to the ability to compensate or adapt to turbulence in the Earth’s atmosphere, removing the blurring of starlight. Adaptive optics systems measure the distortions of the light from a star and then remove the distortions by bouncing the light off a deformable mirror that corrects the image several hundred times per second. The power of AO using natural guide stars has been amply demonstrated in recent years on telescopes up to
Telescopes from AmazonBushnell
By aperture<80mm 80–90mm
resolution is expected to occur with the implementation of AO
on the new generation of large, 8–10 m
The Keck telescope's newly installed AO system leads the way in this respect.
The main components of the Keck adaptive optics system are a wavefront sensor camera,
a fast control computer and a deformable mirror.
The wavefront sensor camera measures distortions due to atmospheric turbulence using light from the guide star.
A control computer computes the wavefront
distortion up to 670 times a second
and sends commands to the deformable mirror.
The deformable mirror, about six inches (15 cm) in diameter,
is made out of a thin sheet of reflective glass controlled by 349 actuators
that can adjust the shape of the mirror by several microns,
a distance large enough to correct for atmospheric distortions.
The Keck II AO Facility was made possible by a grant from the W.M. Keck Foundation and funds from NASA. The Natural Guide Star AO system was fabricated by Keck Observatory and Lawrence Livermore National Laboratory (LLNL provided the wavefront controller).
"First light" Keck II adaptive optics images before and after closing-the-AO-loop on a
V=5.6 A0 star at 0300 HST on 5 February 1999.
The image at H (1.6 µm) improved from 600 milliarcseconds to 44 milliarcseconds
and the Strehl ratio improved by a factor of about 100 to ~25%.
Image: © W.M. Keck Observatory
P. Wizinowich, D.S. Acton, C. Shelton, P. Stomski, J. Gathright, K. Ho, W. Lupton,
K. Tsubota, O. Lai, C. Max, J. Brase, J. An, K. Avicola, S. Olivier, D. Gavel,
B. Macintosh, A. Ghez, and J. Larkin,
"First Light Adaptive Optics Images from the Keck II Telescope: A New Era of High Angular Resolution Imagery,"
P.A.S.P. 112, 315–319 (2000)
Full Press Release
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