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Topic: Segmented mirror

	HighBeam Encyclopedia - telescope
		In a reflecting telescope, or reflector, light is reflected by a concave mirror and brought to a focus in front of the mirror.
		The small secondary mirror, which blocks a negligible portion of the primary mirror, is tilted at an angle of 45° in order to reflect the convergent light at right angles and bring it to a focus outside the telescope tube.
		Equal in importance to the mirrors and lenses constituting the optics of a telescope is the mounting of the telescope.
	www.encyclopedia.com /html/t/telescop.asp (1922 words)

	Dither Sensing for Controlling a Segmented-Mirror Telescope (Site not responding. Last check: 2007-10-29)
		The position and orientation errors of each segment, and the corresponding translational and rotational displacements needed to effect correction, are called "piston" (simple translation along the line of sight) and "tilt" (angular displacements about two axes perpendicular to the line of sight).
		Once the centroid has been located, the segment of interest is tilted to move the subimage cast by that segment to the desired location, which is ordinarily the center of the image plane.
		The piston measurement for each segment is a measurement of the response of the speckle pattern to a small dither of that segment.
	www.nasatech.com /Briefs/May00/MFS31352.html (592 words)

	Thirty Metre Telescope - Telescope
		Each mirror is equipped with sensors so a computer can determine how it is oriented relative to the mirrors around it and correct so that the mirror segments together always form a parabola.
		The reason the TMT has primary, secondary and tertiary mirrors is that it is a Nasmyth telescope (named after its inventor James Nasmyth, a Scottish engineer): it uses what is known as the Nasmyth focus.
		The tertiary mirror is a flat mirror called a Nasmyth flat which reflects the light out of the side of the telescope instead of allowing it to go through a hole in the primary and out the back.
	lot.astro.utoronto.ca /design/tel.html (1616 words)

	3.4 Integral Field Unit Philosophy
		The individual elements of the segmented mirror are located along a parabola with 32 mm focal length, so the virtual slit feeding the spectrograph is flat and beams from the centers of each slitlet are telecentric (i.e., parallel with a virtual pupil at infinity).
		Pupil images near the mirror extremities are defocused and overlap slightly due to the parabolic layout of the segmented mirror array.
		This can be avoided by moving the segmented mirror closer to the image slicer, but at the expense of increasing the displacement angles on the image slicer elements and suffering greater movement of the pupil on the grating.
	msowww.anu.edu.au /nifs/archive/desc/node10.html (1624 words)

	Keck Revolution in Telescope Design Pioneered at Lawrence Berkeley Lab
		The surface of the reflecting mirror of any large telescope is continually subjected to stress from such factors as atmospheric temperature changes, shifting winds, or changes in the mirror's position as it scans the sky.
		Explained Nelson, "Polishing a segment of a parabolic curve is practically impossible, the mirror segment would have to be the shape of a potato chip.
		The space-frame mirror cell that holds the mirror, which consists of more than 1100 individual working pieces, was added next; and on October 12, 1990, the first mirror segment was put into place.
	www.lbl.gov /Science-Articles/Archive/keck-telescope.html (3877 words)

	wgrep
		As the KECK primary mirror consists of relatively thin segments, the overall weight of the 10m telescope is considerably less than that of the 8m telescope.
		The explanation for that is the use of the segmented primary mirror and the alt-az style of mounting, as compared to the equatorial mounting.
		Segmented mirrors also result in much lower overall weight for primaries as compared to single dish meniscus mirrors, with the overall benefit of a much lower telescope mass.
	www.cfht.hawaii.edu /Reference/NGC/wgr/grundmannReport.html (6303 words)

	Segmented mirror systems
		The hexagonal segments are Zerodur, each one measures 1 m from flat to flat and is 50mm thick.
		In practice, the segment size is selected using a mixture of some quantitative cost estimates and some experienced judgment.
		The current consensus is that the optimal segment size is in the 1- to 2-meter-diameter range.
	grus.berkeley.edu /~jrg/MirrorStructure/node4.html (1216 words)

	Coarse Alignment of a Segmented Telescope Mirror
		A method of coarse alignment has been proposed for a primary telescope mirror that comprises multiple segments mounted on actuators that can be used to tilt and translate the segments to effect wavefront control in increments as fine as a fraction of a wavelength of light.
		Operating on each image in turn, vary the piston adjustment of the corresponding mirror segment to concentrate as much light as possible into a smaller focal spot of a given size.
		Tilt all of the outer segments except one to move their images off the detector and to form a dispersed-fringe image by use of the central mirror segment and the remaining outer mirror segment.
	www.nasatech.com /Briefs/Apr01/NPO20770.html (585 words)

	EOS Technologies Mirror Mounts
		Segmented mirror telescopes have made it possible to construct much larger telescopes than are feasible with monolithic mirrors.
		Our specialized segment mounts provide very high linearity and repeatability at a reasonable cost.
		These mounts provide excellent segment wavefront quality and extremely fine motion repeatability for segment adjustment and calibration.
	www.eostech.com /mirror_mounts.php (92 words)

	A Phase Diversity Experiment to Measure Piston Misalignment on the Segmented Primary Mirror of the Keck II Telescope ... (Site not responding. Last check: 2007-10-29)
		Abstract: We are developing a technique to measure segment misalignment of large telescopes based on wavefront estimation using phase-diverse (in- and out-of-focus) images.
		We report the current results of an experiment to measure piston errors on the Keck II primary segmented mirror, through atmospheric turbulence, using phase-diverse phase retrieval.
		The segment piston errorss are separated from the random turbulence by averaging phase estimates from many frames.
	citeseer.ist.psu.edu /533757.html (472 words)

	Hubble Space Telescope - InfoSearchPoint.com (Site not responding. Last check: 2007-10-29)
		The telescope is a reflector with two mirrors; the main mirror has a diameter of about 2.4 meters.
		It was determined that the main mirror had been ground slightly too flat at the edges, a problem that could have been tested for on the ground if the funds had been available.
		For example, the Keck telescope at Mauna Kea in Hawaii has a 10 meters segmented mirror, composed of a mosaic of separate mirrors arranged together and continuously adjusted by a bed of computer controlled actuators to ensure that they maintain their proper shape.
	www.infosearchpoint.com /display/Hubble_Space_Telescope (1485 words)

	The Giant Segmented Mirror Telescope (GSMT)
		The mirror is roughly the same size as a baseball diamond.
		With this approach, and with a much larger mirror, the GSMT can obtain deep images in the short-wavelength portion of the infrared domain that are even crisper and deeper than those obtained by the NGST.
		The pioneering development of the Keck Telescopes' 10--meter mirrors, each of which consists of 36 individual segments, has led to the construction of other segmented-mirror instruments within a now highly developed technological framework.
	www.nas.edu /bpa2/nstier3html/gsmt.htm (394 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		Design issues for a 30-m highly segmented mirror are explored, with emphasis on parametric models of simple, inexpensive segments.
		For a 30-m f/1.5 paraboloidal mirror made of spherical, hexagonal glass segments, with simple warping harnesses and three-point supports, the maximum segment diameter is{approx}100 mm, and the minimum segment thickness is{approx}5 mm.
		Because gravitational deformations in the plate are small, the segment actuators require a stroke of only a few tens of micrometers, and the segment positions can be measured by a wave-front sensor.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20482689 (269 words)

	MEMS, Segmented, Deformable Mirror for Adaptive Optics (Site not responding. Last check: 2007-10-29)
		This project will demonstrate piston and tip/tilt actuation of an array of 500-750 µm-radius hexagonal mirrors with fill factors exceeding 98%.
		The mirrors will actuate above the substrate in a piston motion over a range of greater than 5 µm for astronomy applications and over 20 µm for vision science applications.
		Finally, a scalable interconnect must be investigated that will connect from hundreds to thousands of mirrors.
	www.eecs.berkeley.edu /IPRO/Summary/03abstracts/jhuggins.29.html (91 words)

	AURA NIO: Home
		The Mission of the AURA New Initiatives Office (NIO) is to ensure broad Astronomy Community access to a 30-meter-class telescope contemporary in time with ALMA and NGST, by playing a key role in scientific and technical studies leading to the creation of the Giant Segmented Mirror Telescope.
		In May 2000 the Astronomy and Astrophysics Survey Committee (AASC) recommended, as its highest priority large ground-based initiative for this decade, the construction of a 30-meter aperture Giant Segmented Mirror Telescope (GSMT).
		The AURA New Initiatives Office was formally established in January 2001 to work towards the goal of being able to start construction of GSMT by the end of this decade in order to complement NGST and ALMA.
	www.aura-nio.noao.edu (385 words)

	NOAO - Developing the Future: Giant Segmented Mirror Telescope
		Fabrication options for the manufacture of mirror segments and the polishing thereof; sensors, actuators, etc.
		Site characteristics, based not only on traditional indicators (seeing, transparency vs. wavelength, long-term meteorological observations), but also on the detailed atmospheric structure above the site (critical to the design of AO systems) and wind spectra (critical to evaluating the effects of wind buffeting on both structure and their control systems).
		NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation.
	www.noao.edu /future/gsmt.html (851 words)

	[No title]
		http://gallica.bnf.fr/document?O=N094789 Aitken, R.G. The Mirror of the Crossley Reflector Surfaced with Aluminum.
		The Magic Mirror of Japan, Part I. Proceedings of the Royal Society 28 (1878) 127-148.
		Chanan, G. A., Troy, M. and Ohara, C. Phasing the Primary Mirror Segments of the Keck Telescopes: A Comparison of Different Techniques Design Issues for the Active Control System of the California Extremely Large Telescope (CELT).
	www.europa.com /~telscope/jrnlbibl.txt (13382 words)

	Boston Micromachines—A world leader in deformable mirror systems - Segmented Deformable Mirror
		A segmented membrane allows for decoupled deformation of the actuator array.
		A deflected actuator deforms one mirror pixel only and has no influence on its neighbors.
		1 An array of electrostatic parallel-plate actuators is directly coupled with square mirror pixels by mechanical posts.
	www.bostonmicromachines.com /sdm.html (100 words)

	Modern Rectangular Mirror: Read Reviews, Compare & Prices at NexTag.com
		Boasting a modern, segmented frame, this rectangular mirror will add space and light to any room.
		Segmented with unique channels, the frame is comprised of two ridges that surround the mirror.
		Points between these two ridges are positioned perpendicular ridges, created an illusion of squares being set along the frame.
	nextag.com /Modern-Rectangular-Mirror-Segmented-61223752/prices-html (296 words)

	Boston Micromachines—A world leader in deformable mirror systems - Tutorial
		deformable mirrors are advanced wavefront control devices consisting of a mirror membrane supported by an underlying actuator array.
		Each actuator in the array can be individually deflected by electrostatic actuation to achieve the desired pattern of deformation.
		Unlike piezoelectric mirrors, electrostatic actuation ensures mirror deformation without hysteresis.
	www.bostonmicromachines.com /tutorial.html (80 words)

	California Alumni Association at UC Berkeley (Site not responding. Last check: 2007-10-29)
		Its segmented mirror corrects for atmospheric distortion—the twinkling of stars.
		The target’s shimmering is monitored and the 10-meter mirror continuously recontoured to counteract distortion.
		Long-term observation from Earth has enabled de Pater and her colleagues to study weather on Uranus, as well as features of the rings that only become clear when Earth, Uranus, and the sun are in the right configuration.
	www.alumni.berkeley.edu /Alumni/Cal_Monthly/March_2005/Picture_this.asp (3125 words)

	segmented mirror concept from the Astronomy knowledge base (Site not responding. Last check: 2007-10-29)
		segmented mirror concept from the Astronomy knowledge base
		Next mirror: tertiary mirror Up: mirror Previous mirror: secondary mirror
		has definition A large mirror construction technique in which many smaller elements are built and then actively controlled to conform to the shape of the required large mirror.
	www.site.uottawa.ca:4321 /astronomy/segmentedmirror.html (75 words)

	Strehl Ratio and Modulation Transfer Function for Segmented Mirror Telescopes as a Function of Segment Phase Error (Site not responding. Last check: 2007-10-29)
		We derive the Strehl ratio for a segmented mirror telescope as a function of the rms segment phase error and the observing wavelength, with and without the effects of the atmosphere.
		Although our specific results are in the context of the Keck Telescope, they are presented in a way which should be readily adaptable to other segmented geometries.
		These results are useful in determining how accurately a segmented mirror telescope needs to be phased for a variety of observing applications.
	sirius.ps.uci.edu /~esirko/papers/strehl/gc_strehl.html (153 words)

	Resolving Piston Ambiguities when Phasing a Segmented Mirror - Lofdahl, Eriksson (ResearchIndex) (Site not responding. Last check: 2007-10-29)
		If your firewall is blocking outgoing connections to port 3125, you can use these links to download local copies.
		Abstract: Wavefront sensing in monochromatic light is insensitive to segment piston errors that are a whole number of waves.
		Lofdahl and H. Eriksson, "Resolving piston ambiguities when phasing a segmented mirror," in UV, Optical, and IR Space Telescopes and Instruments VI, J. Breckinridge and P. Jacobsen, eds., vol.
	citeseer.ist.psu.edu /291543.html (393 words)

	Reports and Notes
		TMT R- The Tertiary Mirror Equations of Motion of an "off-altitude-axis
		TMT R- Segmentation Effects on the PSF and exit pupil optical path difference map of a 30-meter ELT
		Cabak, J. A differential, tilt-independent displacement sensor for the CELT mirror
	tmt.ucolick.org /reports_and_notes/index.htm (921 words)

	optical telescope
		The telescope will have a segmented primary mirror and a monolithic secondary...
		An optical telescope is a telescope which is used to gather, and focus, light, for directly viewing...
		In Hawaii, the Keck II telescope has a 33-foot mirror four times the size of Hubble's.
	www.telescopes-guide.com /optical-telescope (706 words)

	Enabling a Giant Segmented Mirror Telescope for the Astronomical Community
		4.5.C. Conceptual Design of Primary Mirror Segment Support System of the GSMT Point Design (PDF)
		4.5.D. Design Study For Testing primary Mirror Segments From A 30-M GSMT Using A Test Plate With Computer Generated Hologram CGH (PDF)
		The Gemini Observatory is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina).
	www.aura-nio.noao.edu /book/index.html (337 words)

	AURA - Update on Thirty Meter Telescope activities
		The following links contain an in-depth explanation of the status of the Giant Segmented Mirror Telescope, AURA’s involvement in a Thirty Meter Telescope, a brief description of the restructured proposal, Questions and Answers, and finally a forum to receive your comments and input.
		AURA is vitally interested in active feedback from the community on this issue.
		+ 07/2005 - A Giant Segmented Mirror Telescope: Its Science and Synergy with JWST: The Power of Two
	www.aura-astronomy.org /nv/nuresult.asp?nuid=67 (367 words)

	[24.04] Toward a Giant Segmented Mirror Telescope: A Progress Report from AURA's New Initiatives Office (Site not responding. Last check: 2007-10-29)
		We present a status report summarizing the efforts of AURA's New Initiatives Office (NIO) and NOAO to advance the first priority ground-based iniltiative of the McKee-Taylor Decadal Survey: completing a 30-m Giant Segmented Mirror Telescope early in the JWST era via a partnership between public and private observatories.
		We summarize (a) the status of GSMT design efforts; (b) the role of the GSMT Science Working Group; (c) the status of the partnership among AURA, ACURA, Caltech and the University of California to design a Thirty Meter Telescope; and (d) NIO and NOAO's efforts to advance other ELT programs.
		The author(s) of this abstract have provided an email address for comments about the abstract: sstrom@noao.edu
	www.aas.org /publications/baas/v35n5/aas203/505.htm (220 words)

	curiousLee - Mike Lee's web log about life and sometimes the design of information, web architectures and technology
		I imagined other people have thought to do this too and hit Google.
		Sure enough, among other random examples, I found an artist in Fairbanks, Alaska named John Reeves who has created two ice sculptures using a segmented vertical water pipe rig and a specially-designed array of spray nozzles.
		The current ice wall, a more ambitious iteration of last year's, is, as of January 22, 2005, 97-feet tall and still growing in temperatures that go as low as 50 below.
	curiouslee.typepad.com (3176 words)

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