Download or read book An Experimental Rayleigh Laser Guide Star Ground Layer Adaptive Optics System for the William Herschel Telescope written by and published by . This book was released on 2005 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Guide Star Adaptive Optics for Astronomy written by N. Ageorges and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive optics allows the theoretical limit of angular resolution to be achieved from a large telescope, despite the presence of turbulence. Thus an eight meter class telescope, such as one of the four in the Very Large Telescope operated by ESO in Chile, will in future be routinely capable of an angular resolution of almost 0.01 arcsec, compared tot he present resolution of about 0.5 arcsec for conventional imaging in good condition. All the world's major telescopes either have adaptive optics or are in the process of building AO systems. It turns out that a reasonable fraction of the sky can be observed using adaptive optics, with moderately good imaging quality, provided imaging in done in the near IR. To move out of the near IR, with its relatively poor angular resolution, astronomers need a laser guide star. There is a layer of Na atoms at approximately 90 km altitude that can be excited by a laser to produce such a source, or Rayleigh scattering can be employed lower in the atmosphere. But the production and use of laser guide stars is not trivial, and the key issues determining their successful implementation are discussed here, including the physics of the Na atom, the cone effect, tilt determination, sky coverage, and numerous potential astronomical applications.
Download or read book Astronomical Adaptive Optics Using Multiple Laser Guide Stars written by Christoph James Baranec and published by . This book was released on with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past several years, experiments in adaptive optics involving multiple natural and laser guide stars have been carried out at the 1.55 m Kuiper telescope and the 6.5 m MMT telescope. The astronomical imaging improvement anticipated from both ground-layer and tomographic adaptive optics has been calculated. Ground-layer adaptive optics will reduce the effects of atmospheric seeing, increasing the resolution and sensitivity of astronomical observations over wide fields. Tomographic adaptive optics will provide diffraction-limited imaging along a single line of sight, increasing the amount of sky coverage available to adaptive optics correction. A new facility class wavefront sensor has been deployed at the MMT which will support closed-loop adaptive optics correction using a constellation of five Rayleigh laser guide stars and the deformable F/15 secondary mirror. The adaptive optics control loop was closed for the first time around the focus signal from all five laser signals in July of 2007, demonstrating that the system is working properly. It is anticipated that the full high-order ground-layer adaptive optics loop, controlled by the laser signals in conjunction with a tip/tilt natural guide star, will be closed in September 2007, with the imaging performance delivered by the system optimized and evaluated. The work here is intended to be both its own productive scientific endeavor for the MMT, but also as a proof of concept for the advanced adaptive optics systems designed to support observing at the Large Binocular Telescope and future extremely large telescopes such as the Giant Magellan Telescope.
Download or read book Advances in Adaptive Optics II written by and published by . This book was released on 2006 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design and Early Results of the Sodium layer Laser Guide Star Adaptive Optics Experiment at the Lawrence Livermore National Laboratory written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive optic systems promise to give diffraction limited performance to ground based telescopes operating at visible and near infrared wavelengths. However, because of the short spatial scale of atmospheric turbulence, the corrected field of view is limited to only a few arc seconds in the visible, to perhaps 10 arc seconds at L band (3.5 [mu]). A bright point source must be in this field of view as a wavefront reference, but the number density of natural stars is too small for full sky coverage at imaging wavelengths less than 3[mu]. A sufficiently bright point source can be artificially generated by a laser however, and investigations into the use of laser beacons has been proceeding for some time now. Our experiments at Livermore have concentrated on the formation of guide stars in the sodium mesospheric layer at 90 km altitude. We have also designed and built adaptive optics systems that use both artificial and natural guide stars. Experimental results to date have shown great promise for the practicality of this technique in astronomy.
Download or read book Performance of Laser Guide Star Adaptive Optics at Lick Observatory written by and published by . This book was released on 1995 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: A sodium-layer laser guide star adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use on the 3-meter Shane telescope at Lick Observatory. The system is based on a 127-actuator continuous-surface deformable mirror, a Hartmann wavefront sensor equipped with a fast-framing low-noise CCD camera, and a pulsed solid-state-pumped dye laser tuned to the atomic sodium resonance line at 589 nm. The adaptive optics system has been tested on the Shane telescope using natural reference stars yielding up to a factor of 12 increase in image peak intensity and a factor of 6.5 reduction in image full width at half maximum (FWHM). The results are consistent with theoretical expectations. The laser guide star system has been installed and operated on the Shane telescope yielding a beam with 22 W average power at 589 nm. Based on experimental data, this laser should generate an 8th magnitude guide star at this site, and the integrated laser guide star adaptive optics system should produce images with Strehl ratios of 0.4 at 2.2 [mu]m in median seeing and 0.7 at 2.2 [mu]m in good seeing.
Download or read book Improved Performance of the Laser Guide Star Adaptive Optics System at Lick Observatory written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 [mu]m were corrected to over 40% of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to ≈10% of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics system using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.
Download or read book Design and Performance Analysis of Adaptive Optical Telescopes Using Laser Guide Stars written by Byron MacMaster Welsh and published by . This book was released on 1989 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric turbulence severely limits the resolution of ground-based astronomical telescopes. In good seeing conditions at the best observatory sites, resolution at visible wavelengths is typically limited to $sim$1 sec of arc. During the past 15 years adaptive optical systems using electrically deformable mirrors have been developed to compensate for turbulence effects. Unfortunately, these systems require bright reference sources adjacent to the object of interest and can be used to observe only the brightest stars. Artificial guide stars suitable for controlling an adaptive imaging system can be created in the upper atmosphere by using a laser to excite either Rayleigh backscattering in the stratosphere or resonance backscattering in the mesospheric Na layer. The design requirements of a laser-guided adaptive telescope, as well as the expected imaging performance, are discussed in detail in this thesis. Analytical expressions giving the performance of a class of adaptive optics systems using slope sensors are derived. The unique analysis takes into account the nonideal characteristics of the wavefront sensor and wavefront correction device, as well as the effects of anisoplanatism. Performance measures include the mean-square residual phase error across the aperture of the optical system and the optical transfer function. We show that a two-meter, ground-based, laser-guided telescope can achieve imaging performance levels at visible wavelengths nearly matching those of the Hubble Space Telescope (HST). The laser power requirement for Rayleigh and Na guide stars is on the order of 33 W and 6 W, respectively, for zenith viewing and r$sp{rm o}$ = 20 cm. Both systems will achieve near diffraction limited imaging with a Strehl ratio of $sim$ 0.73 and an angular resolution of approximately 0.07 arcsec for an observation wavelength of 0.5 $mu$m. In the case of guide stars created in the mesospheric Na layer, saturation effects may significantly reduce the backscattered signal expected for resonance fluorescence lidar systems. The level of saturation is determined by the laser's pulse length, pulse energy, beamwidth and linewidth. Design examples, including lidar systems for atmospheric research and laser-guided telescopes, are studied in detail.
Download or read book Image Improvement from a Sodium layer Laser Guide Star Adaptive Optics System written by and published by . This book was released on 1997 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. Image full widths at half maximum were identical for laser and natural guide stars (0.3 arc seconds). The Strehl ratio with the laser guide star was 65% of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions.
Download or read book Simulation and Analysis of Laser Guide Star Adaptive Optics Systems for the Eight to Ten Meter Class Telescopes written by and published by . This book was released on 1994 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper discusses the design and analysis of laser-guided adaptive optic systems for the large, 8--10 meter class telescopes. We describe a technique for calculating the expected modulation transfer function and the point spread function for a closed loop adaptive optics system, parameterized by the degree of correction and the seeing conditions. The results agree closely with simulations and experimental data, and validate well known scaling law models even at low order correction. Scaling law.model analysis of a proposed adaptive optics system at the Keck telescope leads to the conclusion that a single laser guide star beacon will be adequate for diffraction limited imaging at wavelengths between 1 and 3 am with reasonable coverage of the sky. Cone anisoplanatism will dominate wavefront correction error at the visible wavelengths unless multiple laser guide stars are used.
Download or read book Adaptive Optics for Large Telescopes written by and published by . This book was released on 1992 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optics Letters written by and published by . This book was released on 2007 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Initial Results from the Lick Observatory Laser Guide Star Adaptive Optics System written by and published by . This book was released on 1995 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present initial results from the sodium-layer laser guide star adaptive optics system developed for the 3-m Shane telescope at Lick Observatory.
Download or read book Laser Guide Star Adaptive Optics written by and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Feasibility demonstrations using one to two meter telescopes have confirmed the utility of laser beacons as wavefront references for adaptive optics systems. Laser beacon architectures suitable for the new generation of eight and ten meter telescopes are presently under study. This paper reviews the concept of laser guide star adaptive optics and the progress that has been made by groups around the world implementing such systems. A description of the laser guide star program at LLNL and some experimental results is also presented.
Download or read book The Sodium Laser Guide Star Experiment for Adaptive Optics and the Development of a High Bandwidth Tracking System for the University of Chicago Adaptive Optics System written by Fang Shi and published by . This book was released on 1999 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Guide Stars and Adaptive Optics for Astronomy written by and published by . This book was released on 1992 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: Five papers are included: feasibility experiment for sodium-alyer laser guide stars at LLNL; system design for a high power sodium beacon laser; sodium guide star adaptive optics system for astronomical imaging in the visible and near-infrared; high frame-rate, large field wavefront sensor; and resolution limits for ground-based astronomical imaging. Figs, tabs, refs.
Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 2007 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
