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 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 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 Principles of Adaptive Optics written by Robert K. Tyson and published by CRC Press. This book was released on 2022-02-28 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Principles of Adaptive Optics describes the foundations, principles, and applications of adaptive optics (AO) and its enabling technologies. This leading textbook addresses the fundamentals of AO at the core of astronomy, high-energy lasers, biomedical imaging, and optical communications. Key Features: Numerous examples to explain and support the underlying principles Hundreds of new references to support the topics that are addressed End-of-chapter questions and exercises A complete system design example threaded through each chapter as new material is introduced
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Adaptive Optics written by Robert Tyson and published by CRC Press. This book was released on 2010-09-14 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the publication of the second edition of Principles of Adaptive Optics, the developments and applications in this area have increased tremendously. Observatories are now producing outstanding science through adaptive optics technology; components, such as micromachined deformable mirrors and very low noise detectors, are revolutionizing the f
Download or read book Adaptive Optics in Astronomy written by François Roddier and published by Cambridge University Press. This book was released on 1999-06-17 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive optics is set to revolutionise the future of astronomy; this is the first book on the subject and is set to become the standard reference.
Download or read book Adaptive Optics for Astronomy written by D.M. Alloin and published by Springer Science & Business Media. This book was released on 1994-03-31 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: The blossoming of adaptive optical techniques has brought about a revolution in the field of astronomical observation. Coupled with the new generation of large, ground-based telescopes, it allows us to achieve an unprecendented angular resolution in the analysis of faint astronomical sources at optical wavelengths. This book provides the basic concepts of adaptive optics, discusses the possible instrumental strategies and the state-of-the-art technical achievements of this development and presents the key astrophysical programs which will most benefit from it. Over fifteen well-known experts have contributed to making this volume a comprehensive one, with steady progression as well as full coverage of the various aspects of the field. Students graduating in optical sciences and astrophysics, astronomers, engineers interested in atmospheric turbulence compensation will find this book a reference text on the subject.
Download or read book Adaptive Optics written by Michael S. Tarov and published by Nova Publishers. This book was released on 2002 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive optics is a field which is coming into its own with new discoveries occurring almost daily both in astronomy and in applications of AO in applied fields. In an adaptive optics system, the output from a wavefront sensor is used to calculate corrections that actively remove distortions from an image. The applications of adaptive optics in vision science have received considerable impetus from the knowledge developed by astronomers about how to correct images using AO technology. It is expected that developments in adaptive optics will radically change the face of astronomy in the 21st century. These systems will largely overcome the main limitation of ground-based telescopes, namely the severe reduction in image quality caused by turbulence in the Earth's atmosphere. Intended for use at near infrared wavelengths, adaptive optics allow imaging and spectroscopy at the limit of resolution imposed by optical diffraction an advance in astronomer's ability to view the heavens unparalleled since the invention of the telescope. AO is now also entering clinical medicine in the field of ophthalmology and other related fields. This new book presents several hundred current abstracts in the field, each fully indexed, for ease of access and contains a CD ROM for further research.
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 Introduction to Adaptive Optics written by Robert K. Tyson and published by SPIE Press. This book was released on 2000 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive optics systems and components have achieved a level of sophistication and simplicity that goes beyond traditional applications in astronomy and the military and into developments in medicine, manufacturing, and communications. This book was written for those interested in the multidisciplinary technology and those who need a broad-brush explanation without wading through thousands of journal articles. It follows the structure of a one-day tutorial taught by the author, including humor and sidebars of historical material.
Download or read book Adaptive Optical Systems and Applications written by Robert K. Tyson and published by . This book was released on 1995 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Modeling of Laser Guide Star Wavefront Sensing for Extremely Large Telescopes written by Kathryn J. Jackson and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a simulation of the control system for Laser Guide Star (LGS)wavefront sensing of the Narrow Field Infrared Adaptive Optics System (NFIRAOS)which will be the Adaptive Optics (AO) system on the Thirty Meter Telescope. Thecontrol system is multirate and combines data from multiple sources, both naturaland artificial, to provide wavefront correction. Artificial guide stars are generated byexciting atoms in the mesospheric sodium (Na) layer. The characteristics of the Na layer have been examined; its variability, altitudeand thickness will lead to false atmospheric turbulence measurements by AO systemsintegrated with Extremely Large Telescopes. A periodically updated constrainedmatched filter algorithm has been implemented in the control system simulation inorder to gauge its ability to mitigate these effects. The control system has also been implemented on the University of Victoria LGSTest Bench which reproduces wavefront measurements as they will be made by severalof the wavefront sensors of NFIRAOS. The simulation has provided insight into thestability of the proposed control system and allowed necessary improvements to bemade. It has been shown to meet the requirements of stability over long term withfast convergence. The matched filter algorithm has been shown to effectively rejectthe Na layer fluctuations both in simulation and on the test bench.
Download or read book Modeling of Laser Guide Star Wavefront Sensing for Extremely Large Telescopes written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a simulation of the control system for Laser Guide Star (LGS) wavefront sensing of the Narrow Field Infrared Adaptive Optics System (NFIRAOS) which will be the Adaptive Optics (AO) system on the Thirty Meter Telescope. The control system is multirate and combines data from multiple sources, both natural and artificial, to provide wavefront correction. Artificial guide stars are generated by exciting atoms in the mesospheric sodium (Na) layer. The characteristics of the Na layer have been examined; its variability, altitude and thickness will lead to false atmospheric turbulence measurements by AO systems integrated with Extremely Large Telescopes. A periodically updated constrained matched filter algorithm has been implemented in the control system simulation in order to gauge its ability to mitigate these effects. The control system has also been implemented on the University of Victoria LGS Test Bench which reproduces wavefront measurements as they will be made by several of the wavefront sensors of NFIRAOS. The simulation has provided insight into the stability of the proposed control system and allowed necessary improvements to be made. It has been shown to meet the requirements of stability over long term with fast convergence. The matched filter algorithm has been shown to effectively reject the Na layer fluctuations both in simulation and on the test bench.
Download or read book Tip tilt Compensation written by and published by . This book was released on 1992 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The angular resolution of long-exposure images from ground-based telescopes equipped with laser guide star adaptive optics systems is fundamentally limited by the the accuracy with which the tip-tilt aberrations introduced by the atmosphere can be corrected. Assuming that a natural star is used as the tilt reference, the residual error due to tilt anisoplanatism can significantly degrade the long-exposure resolution even if the tilt reference star is separated from the object being imaged by a small angle. Given the observed distribution of stars in the sky, the need to find a tilt reference star quite close to the object restricts the fraction of the sky over which long-exposure images with diffraction limited resolution can be obtained. In this paper, the authors present a comprehensive performance analysis of tip-tilt compensation systems that use a natural star as a tilt reference, taking into account properties of the atmosphere and of the Galactic stellar populations, and optimizing over the system operating parameters to determine the fundamental limits to the long-exposure resolution. Their results show that for a ten meter telescope on Mauna Kea, if the image of the tilt reference star is uncorrected, about half the sky can be imaged in the V band with long-exposure resolution less than 60 milli-arc-seconds (mas), while if the image of the tilt reference star is fully corrected, about half the sky can be imaged in the V band with long-exposure resolution less than 16 mas. Furthermore, V band images long-exposure resolution of less than 16 mas may be obtained with a ten meter telescope on Mauna Kea for unresolved objects brighter than magnitude 22 that are fully corrected by a laser guide star adaptive optics system. This level of resolution represents about 70% of the diffraction limit of a ten meter telescope in the V band and is more than a factor of 45 better than the median seeing in the V band on Mauna Kea.
