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Topic: Laser guide star

	SPACE.com -- New 'Star' in Night Sky to Change View of Cosmos
		The laser light that creates the virtual star is seen emanating from a device attached to the Keck II telescope.
		The light from both the real star and the artificial "guide" star, as it is known, enters the main tube of the telescope.
		The guide star project was funded by the W. Keck Foundation, NASA and the National Science Foundation and developed with the help of the Lawrence Livermore National Laboratory.
	www.space.com /scienceastronomy/astronomy/virtual_star_020104.html (890 words)

	Laser Guide Star Encyclopedia Articles @ NaturalResearch.org (Natural Research) (Site not responding. Last check: )
		Sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics.
		Because the laser beam is deflected by astronomical seeing on the way up, the laser light moves around in the sky in a random fashion.
		As of 2006, only two laser guide star AO systems are regularly used for science observations and have produced published results in the peer-reviewed scientific literature: those at Lick Observatory and Palomar Observatory in California, and Keck Observatory in Hawaii.
	www.naturalresearch.org /encyclopedia/Laser_guide_star (542 words)

	laser in Lasers. Page 1
		A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam.
		The "first-light" for the Keck laser was a complete success with the laser guide star being propagated for the first time at 11:42 UT, December 23 2001.
		Lasers are used in CD players, dental drills, eye surgery, and even tattoo removal.
	www.aledir.com /Lasers/laser (265 words)

	Laser guide star teams with adaptive optics to shed light on massive star formation
		Many other groups are developing lasers to be used as guide stars, but Max's group has been ahead of its competitors since first demonstrating the concept in the early 1990s at Livermore.
		Since then, she and colleagues have been perfecting the laser and the software that allows the mirror - in the case of Lick's 120-inch telescope, a 3-inch secondary mirror inside the main telescope - to be flexed just right to remove the twinkle from stars.
		Max and her colleagues have tested an identical laser guide star system at the Keck Telescopes in Hawaii, but it is not yet ready for routine use, she said.
	www.eurekalert.org /pub_releases/2004-02/uoc--lgs022304.php (1602 words)

	Lick AO System Info (Site not responding. Last check: )
		In NGS mode observing, the guide star must be at least as bright as 12'th R-magnitude.
		The laser control system is being upgraded this year to minimize the number of laser operators and to provide integration to the AO system and telescope systems.
		New guide star sensitivity graphs are based on photometric measurements made during in the 2000 engineering campaigns.
	mthamilton.ucolick.org /techdocs/instruments/AO/index.html (1342 words)

	Scientists See Better, Fainter with New Keck Laser Guide Star (Site not responding. Last check: )
		The laser lets scientists explore most of the sky with adaptive optics and gives them the capability to study objects that were previously too faint to be seen with the system.
		Regularly using sodium lasers with adaptive optics is in its early stages, but laser guide stars are being developed for most major observatories, most notably the European Southern Observatory’s Very Large Telescope, the Gemini North and Gemini South telescopes and the National Astronomical Observatory of Japan’s Subaru Telescope.
		Plans are also underway to install a new laser guide star system on the Keck I telescope within the next three years, and also to improve the efficiency and reliability of the existing laser system on Keck II.
	www.keckobservatory.org /news/science/060110_lgs/index.html (1297 words)

	Laser Guide Stars (Site not responding. Last check: )
		A laser guide star is beamed out the open dome of Lick Observatory atop Mt. Hamilton, east of San Jose, Ca., in the first ever test of a laser guide star combined with adaptive optics on a large astronomical telescope.
		The laser reflects off the sodium layer in the upper atmosphere, at an altitude of 60 miles, thus creating a manmade guide star.
		The star serves as a focal point for a computer-driven membrane-thin mirror with 127 individual actuators glued to the back of it - tiny plungers that can adjust minute portions of the mirror 50-100 times per second to counteract the effects of atmospheric turbulence.
	www.coseti.org /lasrstar.htm (142 words)

	ChAOS Sodium Laser Guide Star Experiments (Site not responding. Last check: )
		The basic requirements for the artificial star are that it be bright for a better signal-to-noise ratio in the wavefront sensor and small in size for better accuracy in determining the wavefront distortions.
		During the experiments, the VTT was used to send the laser beam up to the sodium layer and to simultaneously observe the returning light from the artificial star.
		Sodium laser guide star and the star Eta UMa in the V band.
	astro.uchicago.edu /chaos/sac_peak_laser.html (394 words)

	Astrophysicists Use Laser Guide Star Adaptive Optics
		Using the laser guide star adaptive optics system created by LLNL scientists, the team was able to determine that some of the relatively young yet massive Herbig Ae/Be stars contain biconical nebulae, polarized jets and circumstellar disks.
		The laser guide star enables astronomers to study nearly the entire sky with the high resolution of adaptive optics.
		These stars are thought to be the young stage of the massive stars that later experience supernova explosions and trigger star formation in nearby clouds.
	www.spacedaily.com /news/telescopes-04a.html (572 words)

	Altair Laser Guide Star
		The Gemini Mauna Kea Laser Guide Star System is designed to extend the use of Altair for targets for which a bright natural star is unavailable for adaptive optics correction.
		A natural tip/tilt star is still needed for the low-order tip/tilt correction, but this star need not be very bright nor very close when compared to correcting all orders on a Natural Guide Star (NGS).
		Laser propagation can only be done under photometric conditions and the guide loops are only stable for decent seeing.
	www.gemini.edu /sciops/instruments/altair/altairLaserGuideStar.html (1371 words)

	Clear view of star formation
		The laser is the final piece of the laser guide star adaptive optics system that allows twinkle-free viewing of the entire nighttime sky.
		Since then, she and colleagues have been perfecting the laser and the software that allows the mirror--in the case of Lick's 120-inch telescope, a 3-inch secondary mirror inside the main telescope--to be flexed just right to remove the twinkle from stars.
		The dye laser is pumped by a green neodymium YAG laser, a bigger brother to the readily available green milliwatt laser pointers.
	currents.ucsc.edu /03-04/03-01/images.html (1588 words)

	Sodium Laser Guide Stars
		It seems particularly appropriate to have projected the first sodium laser guide star from a site where a large telescope is currently pushing forward on AO technology.
		In fact, the first laser guided AO system at Starfire Optical Range was built for a 1.5-m telescope in the years 1987 to 1990.
		When I first visited the 1.5-m laser guided telescope at Starfire Optical Range, it was like deja vu: a Rayleigh laser guided AO system with all the characteristics of the design papers Gardner and I had been publishing.
	www.astro.uiuc.edu /~thompson/aohist.html (1395 words)

	ESO MCAO
		Laser guide stars (LGS) projectors have now been deployed on a number of 4 m-class telescopes and are basically part of every 8-10 m-class project.
		Due to the bright (m~10) artificial star created near the center of the field, cumulative sky coverage, or the probability to achieve a given minimum Adaptive Optics (AO) correction on an arbitrary astronomical target, goes e.g.
		A (possibly fainter/farther from the center of the field) NGS is still needed to correct stellar agitation (tip/tilt), since it cannot be sensed from an LGS; this is why sky coverage is not 100% and goes down for better corrections.
	www.eso.org /projects/aot/laser (332 words)

	Adaptive Optics - Monochromatic and Polychromatic Laser Guide Stars (Site not responding. Last check: )
		Adaptive Optics - Monochromatic and Polychromatic Laser Guide Stars
		This can be done only with a fifth order correction on a natural star near or with a third order and three natural star (in both cases with a faint sky coverage, specialy at the visible wavelengths), or with a polychromatic laser guide star.
		PASS was setup at Lawrence Livermore National Laboratory telescope and the image shifts at the polycromatic laser guide star various wavelenghts were measured on the telescope focus.
	www-obs.univ-lyon1.fr /~airi/laser.html (494 words)

	ESO's VLT Launches Laser Guide Star
		ESO ignited a laser beam of several watts on Jan. 28 at Yepun, the fourth 8.2-meter telescope in the array.
		The artificial star, located 90 kilometers (57.6 miles) up in the atmosphere, is about 20 times fainter than the faintest star that can be seen with the unaided eye, but it is bright enough for the VLT's adaptive optics to measure and correct atmospheric blurring, thereby giving astronomical images much greater clarity.
		The guide star is the culmination of five years of collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany.
	www.spacedaily.com /reports/ESOs_VLT_Launches_Laser_Guide_Star.html (839 words)

	Center for Adaptive Optics \| Newsletter vol. 2
		Operators were very satisfied with the brightness of the laser guide star spot at the 100-km altitude of the sodium layer and the fact that the low-altitude laser beam emission (due to Rayleigh scattering) was at the low level predicted.
		Plans to further optimize the laser and to fully integrate the laser guide star with the Keck II adaptive optics system are proceeding.
		The laser creates a “virtual” star high above the Earth’s surface, which is not visible to the human eye, but is bright enough to guide high resolution adaptive optics at Keck.
	cfao.ucolick.org /pubs/newsletters/02/firstlight.shtml (328 words)

	A laser guide star video \| Laser Web
		Thanks to their dedicated efforts, they were able to create the first artificial star in the Southern Hemisphere, allowing astronomers to study the Universe in the finest detail.
		This artificial laser guide star makes it possible to apply adaptive optics systems, that counteract the blurring effect of the atmosphere, almost anywhere in the sky.
		It explains the principle of laser guide star well.
	laserweb.org /node/684 (187 words)

	Demetrius at The Australian National University: Item 1885/41345
		The aim of this project is to develop a novel, high average power source of highly coherent radiation at the 589nm sodium D2 resonance line for use in creating a laser guide star for use with adaptive optics systems such as astronomical telescopes and satellite ranging.
		A laser guide star provides a beacon which combined with a wavefront sensor allows the effect of the atmosphere to be quantified and mechanical corrections made to the adaptive optics in the telescope to cancel those distortions.
		Whilst laser guide stars have been demonstrated as effective in a number of astronomical observatories, at present there is no laser technology that dominates this application.
	hdl.handle.net /1885/41345 (359 words)

	Adaptive Optics at Lick Observatory
		Essentially, when a celestial object is to be observed, a fairly bright star nearby is monitored, and a correction is made for the "twinkle" that is observed.
		Since a natural guide star is not always present near the object to be observed, Lick astronomers and scientists from Lawrence Livermore National Labs have engineered the world’s first laser guide star system routinely used for science.
		By shooting a laser beam into the sky near the object to be observed, astronomers create an artificial "star" of glowing atmospheric sodium ions.
	www.ucolick.org /public/ao.html (446 words)

	Laser History - Laser Guide Stars
		Like the gasdynamic laser this invention is a product of top secret military research on the 'Star Wars' laser defense program to allow high power ground based lasers to traverse the atmosphere without distortion, bounce off orbiting mirrors and shoot down intercontinental ballistic missiles.
		There are many prototype laser guide star systems currently in operation or in the testing phase such as the Lick Observatory system.
		Laser guide star systems can offer an elegant solution to this problem by actively rather than passively sensing these inhomogenieties.
	laserstars.org /history/LaserGuideStars.html (2172 words)

	First Light for Laser Guide Star at Very Large Telescope \| SpaceRef - Your Space Reference
		Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere’s blurring effect.
		An intense and exhilarating twelve days of tests followed the First Light of the Laser Guide Star (LGS), during which the LGS was used to improve the resolution of astronomical images obtained with the two adaptive optics instruments in use at Paranal: the NAOS-CONICA imager and the SINFONI spectrograph.
		The experience gained with this Laser Guide Star is also a key milestone in the design of the next generation of Extremely Large Telescope in the 30 to 60 metre range that is now being studied by ESO and its community of users.
	www.spaceref.com /news/viewpr.html?pid=19100 (1005 words)

	Palomar Observatory: Adaptive Optics at Palomar Observatory
		The adaptive optics system uses a star as a calibration source and then deforms a small mirror to correct for distortions caused by the atmosphere.
		In places where there isn’t a natural guide star near the object of interest, the technique cannot generally be used.
		The laser beam is too faint to be seen except by observers very close to the telescope, and the guide star it creates is even fainter.
	www.astro.caltech.edu /palomar/AO (469 words)

	laser in Lasers at Coderdir.com. Page 1
		fact that the low-altitude laser beam emission (due to Rayleigh scattering...
		was the first person to use the word "laser".
		There is good reason to believe that Gordon Gould made the first light laser.
	www.coderdir.com /Lasers/laser (265 words)

	Mesosphere Sodium Column Density and the Sodium Laser Guide Star Brightness - Ge (ResearchIndex)
		Abstract: The #rst time simultaneous measurements of sodium column density and the absolute #ux from a sodium laser guide star, created by a monochromatic 3 W cw laser, tuned to the peak of the sodium D 2 hyper#ne structure, were conducted at the MMT and CFA 60 inch telescope in 1997.
		The results show that linearly and circularly polarized laser returns are proportional to the simultaneous sodium column density.
		Ge et al., "Mesosphere sodium column density and the sodium laser guide star brightness," Proc.
	citeseer.ist.psu.edu /298354.html (382 words)

	ALFA Current Status
		The sodium laser guide star adaptive optics system ALFA, which is installed at the Calar Alto 3.5-m telescope, has been undergoing an intensive optimisation phase.
		Correcting tip-tilt on a star 41" away and higher orders on the laser, we achieved in increase in peak intensity of 2.5, and a reduction in FWHM from 1.07" to 0.40".
		For the second time ALFA was locked on the laser guide star while images on BD 31643 were taken.
	www.mpia-hd.mpg.de /ALFA/MENU/status.html (815 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		The rms spot motion at the higher laser powers, with active beam-pointing control, was less than 0.5 arcsec and had little effect on the observed spot size under these conditions.
		With a transmitted power of 1100 W and an atmospheric transmission of 0.6, the irradiance from the guide star at the ground was 10 (photons/cm{sup 2})/ms, corresponding to a visual magnitude of 5.1.
		The implications for the performance of wave-front sensors with a laser guide star of this magnitude and resulting closed-loop adaptive-optics performance are discussed.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=272760 (288 words)

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