Search

Ground-layer adaptive optics (GLAO) systems offer the possibility of improving the "seeing" of large ground-based telescopes and increasing the efficiency and sensitivity of observations over a wide field-of-view. We explore the utility and feasibility of deploying a GLAO system at the W. M. Keck Observatory in order to feed existing and future multi-object spectrographs and wide-field imagers. We also briefly summarize science cases spanning exoplanets to high-redshift galaxy evolution that would benefit from a Keck GLAO system. Initial simulations indicate that a Keck GLAO system would deliver a 1.5x and 2x improvement in FWHM at optical (500 nm) and infrared (1.5 micron), respectively. The infrared instrument, MOSFIRE, is ideally suited for a Keck GLAO feed in that it has excellent image quality and is on the telescope's optical axis. However, it lacks an atmospheric dispersion compensator, which would limit the minimum usable slit size for long-exposure science cases. Similarly, while LRIS and DEIMOS may be able to accept a GLAO feed based on their internal image quality, they lack either an atmospheric dispersion compensator (DEIMOS) or flexure compensation (LRIS) to utilize narrower slits matched to the GLAO image quality. However, some science cases needing shorter exposures may still benefit from Keck GLAO and we will investigate the possibility of installing an ADC., Comment: 2018 Proceedings of the SPIE; published

Since 2013, observations of Neptune with small telescopes have resulted in several detections of long-lived bright atmospheric features that have also been observed by large telescopes such as Keck II or Hubble. The combination of both types of images allows the study of the long term evolution of major cloud systems in the planet. In 2013 and 2014 two bright features were present on the planet at southern mid latitudes. These may have merged in late 2014, possibly leading to the formation of a single bright feature observed during 2015 at the same latitude. This cloud system was first observed in January 2015 and nearly continuously from July to December 2015 in observations with telescopes in the 2 to 10 meter class and in images from amateur astronomers. These images show the bright spot as a compact feature at 40.1 deg South planetographic latitude well resolved from a nearby bright zonal band that extended from 42 deg South to 20 deg South. Tracking its motion from July to November 2015 suggests a longitudinal oscillation of 16 deg in amplitude with a 90 day period, typical of dark spots on Neptune and similar to the Great Red Spot oscillation in Jupiter. The limited time covered by high-resolution observations only covers one full oscillation and other interpretations of the changing motions could be possible. HST images in September 2015 show the presence of a dark spot at short wavelengths in the southern flank of the bright cloud observed throughout 2015., 54 pages, 23 figures, 6 tables

One important frontier for astronomical adaptive optics (AO) involves methods such as Multi-Object AO and Multi-Conjugate AO that have the potential to give a significantly larger field of view than conventional AO techniques. A second key emphasis over the next decade will be to push astronomical AO to visible wavelengths. We have conducted the first laboratory simulations of wide-field, laser guide star adaptive optics at visible wavelengths on a 10-meter-class telescope. These experiments, utilizing the UCO/Lick Observatory's Multi-Object / Laser Tomography Adaptive Optics (MOAO/LTAO) testbed, demonstrate new techniques in wavefront sensing and control that are crucial to future on-sky MOAO systems. We (1) test and confirm the feasibility of highly accurate atmospheric tomography with laser guide stars, (2) demonstrate key innovations allowing open-loop operation of Shack-Hartmann wavefront sensors (with errors of ~30 nm) as will be needed for MOAO, and (3) build a complete error budget model describing system performance. The AO system maintains a performance of 32.4% Strehl on-axis, with 24.5% and 22.6% at 10" and 15", respectively, at a science wavelength of 710 nm (R-band) over the equivalent of 0.8 seconds of simulation. The MOAO-corrected field of view is ~25 times larger in area than that limited by anisoplanatism at R-band. Our error budget is composed of terms verified through independent, empirical experiments. Error terms arising from calibration inaccuracies and optical drift are comparable in magnitude to traditional terms like fitting error and tomographic error. This makes a strong case for implementing additional calibration facilities in future AO systems, including accelerometers on powered optics, 3D turbulators, telescope and LGS simulators, and external calibration ports for deformable mirrors., Comment: 29 pages, 11 figures, submitted to PASP

During the first-light run of the Gemini Planet Imager (GPI) we obtained K-band spectra of exoplanets HR 8799 c and d. Analysis of the spectra indicates that planet d may be warmer than planet c. Comparisons to recent patchy cloud models and previously obtained observations over multiple wavelengths confirm that thick clouds combined with horizontal variation in the cloud cover generally reproduce the planets' spectral energy distributions. When combined with the 3 to 4 um photometric data points, the observations provide strong constraints on the atmospheric methane content for both planets. The data also provide further evidence that future modeling efforts must include cloud opacity, possibly including cloud holes, disequilibrium chemistry, and super-solar metallicity., Comment: Accepted for publication in ApJ

The Gemini Planet Imager instrument's adaptive optics (AO) subsystem was designed specifically to facilitate high-contrast imaging. It features several new technologies, including computationally efficient wavefront reconstruction with the Fourier transform, modal gain optimization every 8 seconds, and the spatially filtered wavefront sensor. It also uses a Linear-Quadratic-Gaussian (LQG) controller (aka Kalman filter) for both pointing and focus. We present on-sky performance results from verification and commissioning runs from December 2013 through May 2014. The efficient reconstruction and modal gain optimization are working as designed. The LQG controllers effectively notch out vibrations. The spatial filter can remove aliases, but we typically use it oversized by about 60% due to stability problems., Adaptive Optics Systems IV, June 22-27, 2014, Series: Proceedings of SPIE; no. 9148

We provide one of the first constraints on the combined infrared single-scattering albedo and opacity of Neptune's upper tropospheric cloud layer. For the observations, we used the adaptive optics system on the Lick Observatory's 3 m Shane Telescope (Mount Hamilton, California). The cloud layer is thought to be composed of H2S and extend up to 3.5–4.5 bars. Previously, the single-scattering albedo was measured in the range 0.2–0.94 μm and found to be extremely high (>0.8), but decreasing with increasing wavelength. Assuming an optically thick cloud, we find the best-fit single-scattering albedo of a 3.5 bar layer to be 0.23 at 1.27 μm and 0.18 at 1.56 μm. Uncertainties in the column density of haze above the cloud layer, and from deconvolution to remove contaminating light scattered by the point-spread function from infrared-bright features, indicate that the cloud could be even darker, but it is unlikely to be brighter than we report. The cloud particles could be brighter than we report if the total near-infrared opacity of the cloud is very low or the cloud's scattering phase function is significantly more forward-scattering at 1.2–1.6 μm than at 0.75 μm.

The ability to simulate atmospheric turbulence in the laboratory is a crucial part of testing and developing astronomical adaptive optics (AO) technology. We report on the development of a technique for creating phase plates that involves the strategic application of clear acrylic paint onto a transparent substrate. Results of interferometric characterization of these plates are described and compared to Kolmogorov statistics. The range of r(0) (Fried's parameter) achieved thus far is 0.2-1.2 mm, with a Kolmogorov power law. These phase plates have been successfully used by the Laboratory for Adaptive Optics at University of California, Santa Cruz in the Multi-Conjugate Adaptive Optics testbed as part of the Visible Light Laser Guidestar Experiments (Villages) calibration system and during integration and testing of the Gemini Planet Imager. Measurements of the turbulence from the plate in Villages are compared to the sky, which shows the plate produces good representative atmospheric aberrations. We are now distributing the plates to other members of the AO community.

Micro-electro-mechanical systems (MEMS) technology can provide for deformable mirrors (DMs) with excellent performance within a favorable economy of scale. Large MEMS-based astronomical adaptive optics (AO) systems such as the Gemini Planet Imager are coming on-line soon. As MEMS DM end-users, we discuss our decade of practice with the micromirrors, from inspecting and characterizing devices to evaluating their performance in the lab. We also show MEMS wavefront correction on-sky with the "Villages" AO system on a 1-m telescope, including open-loop control and visible-light imaging. Our work demonstrates the maturity of MEMS technology for astronomical adaptive optics., 14 pages, 15 figures, Invited Paper, SPIE Photonics West 2012

W. M. Keck Observatory (WMKO) is currently engaged in the design of a powerful new Adaptive Optics (AO) science capability providing precision correction in the near-IR, good correction in the visible, and faint object multiplexed integral field spectroscopy. Improved sensitivity will result from significantly higher Strehl ratios over narrow fields (< 30" diameter) and from lower backgrounds. Quantitative astronomy will benefit from improved PSF stability and knowledge. Strehl ratios of 15 to 25% are expected at wavelengths as short as 750 nm. A multi-object AO approach will be taken for the correction of multiple science targets over modest fields of regard (< 2' diameter) and to achieve high sky coverage using AO compensated near-IR tip/tilt sensing. In this paper we present the conceptual design for this system including discussion of the requirements, system architecture, key design features, performance predictions and implementation plans.

We used laser guide star adaptive optics at the Lick and Keck Observatories to study active galactic nuclei and galaxies, with emphasis on those in the early Universe. The goals were to observe large galaxies like our own Milky Way in the process of their initial assembly from sub-components, to identify central active galactic nuclei due to accreting black holes in galaxy cores, and to measure rates of star formation and evolution in galaxies. In the distant universe our focus was on the GOODS and GEMS fields (regions in the Northern and Southern sky that include the Hubble Deep Fields) as well as the Extended Groth Strip and COSMOS fields. Each of these parts of the sky has been intensively studied at multiple wavelengths by the Hubble Space Telescope, the Chandra X-Ray Observatory, the XMM Space Telescope, the Spitzer Space Telescope, and several ground-based telescopes including the Very Large Array radio interferometer, in order to gain an unbiased view of a significant statistical sample of galaxies in the early universe.

Most current astronomical adaptive optics (AO) systems rely on the availability of a bright star to measure the distortion of the incoming wavefront. Replacing the guide star with an artificial laser beacon alleviates this dependency on bright stars and therefore increases sky coverage, but it does not eliminate another serious problem for AO observations. This is the issue of PSF variation with time and field position near the guide star. In fact, because a natural guide star is still necessary for correction of the low-order phase error, characterization of laser guide star (LGS) AO PSF spatial variation is more complicated than for a natural guide star alone. We discuss six methods for characterizing LGS AO PSF variation that can potentially improve the determination of the PSF away from the laser spot, that is, off-axis. Calibration images of dense star fields are used to determine the change in PSF variation with field position. This is augmented by AO system telemetry and simple computer simulations to determine a more accurate off-axis PSF. We report on tests of the methods using the laser AO system on the Lick Observatory Shane Telescope. [Abstract truncated.], 31 pages, 5 figures, accepted by PASP

Measurements of anisoplanatism from data obtained with natural guide star adaptive optics on the Lick Observatory 3m are presented. These were obtained from short exposures of binary stars with the IRCAL camera whose field of view (~20”) is generally considered isoplanatic in the K-band. However, measurable amounts of high-order anisoplanatism were present at separations of ~7” and ~12” with an isoplanatic patch size estimated to be ~26”. Within this field, there was measureable differential image motion between the binary star components. This image motion was small compared to the size of the diffraction-spot and therefore had negligible effect.

The Lick Observatory laser guide star adaptive optics system has undergone continual improvement and testing as it is being integrated as a facility science instrument on the Shane 3 meter telescope. Both Natural Guide Star (NGS) and Laser Guide Star (LGS) modes are now used in science observing programs. We report on system performance results as derived from data taken on both science and engineering nights and also describe the newly developed on-line techniques for seeing and system performance characterization. We also describe the future enhancements to the Lick system that will enable additional science goals such as long-exposure spectroscopy.

An automated robotic workcell to classify hazardous waste stream items with previously unknown characteristics is designed, tested and demonstrated. The object attributes being quantified are radiation signature, metal content, and object orientation and volume. Multi-sensor information is used to make segregation decisions and to perform automatic grasping of objects. The workcell control program uses an off-line programming system as a server to perform both simulation control as well as actual hardware control of the workcell. The overall workcell layout, sensor specifications, workcell supervisory control, 2-D vision-based automated grasp planning, and object classification algorithms are discussed. >

Even though the technology of adaptive optics (AO) is rapidly maturing, calibration of the resulting images remains a major challenge. The AO point-spread function (PSF) changes quickly both in time and position on the sky. In a typical observation the star used for guiding will be separated from the scientific target by 10" to 30". This is sufficient separation to render images of the guide star by themselves nearly useless in characterizing the PSF at the off-axis target position. A semi-empirical technique is described that improves the determination of the AO off-axis PSF. The method uses calibration images of dense star fields to determine the change in PSF with field position. It then uses this information to correct contemporaneous images of the guide star to produce a PSF that is more accurate for both the target position and the time of a scientific observation. We report on tests of the method using natural-guide-star AO systems on the Canada-France-Hawaii Telescope and Lick Observatory Shane Telescope, augmented by simple atmospheric computer simulations. At 25" off-axis, predicting the PSF full width at half maximum using only information about the guide star results in an error of 60%. Using an image of a dense star field lowers this error to 33%, and our method, which also folds in information about the on-axis PSF, further decreases the error to 19%., 29 pages, 9 figures, accepted for publication in the PASP

Adaptive optics performance using a sodium laser guide star at the Lick Observatory 3.0 m telescope is presented. In order to accomplish this the residual effects of natural guide star tip-tilt motion is removed. This is measured from 500 short exposure images (texp = 57ms). The data show instantaneous Strehl ratios ranging from ~ 0.10 to ~ 0.45 with a mean value of ~ 0.26. Centroid tracking of these data yield residual tip-tilt errors of ~ 21 mas, within specifications for the system. This resdual tip-tilt motion reduces the Strehl ratio of long exposure imaging by only ~ 7%.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In 1999, we presented our plan to upgrade the adaptive optics (AO) system on the Lick Observatory Shane telescope (3m) from a prototype instrument pressed into field service to a facility instrument. This paper updates the progress of that plan and details several important improvements in the alignment and calibration of the AO bench. The paper also includes a discussion of the problems seen in the original design of the tip/tilt (t/t) sensor used in laser guide star mode, and how these problems were corrected with excellent results.

The Lick Observatory laser guide star adaptive optics system has been significantly upgraded over the past two years in order to establish it as a facility science instrument on the Shane 3 meter telescope. Natural Guide Star (NGS) mode has been in use in regular science observing programs for over a year. The Laser Guide Star (LGS) mode has been tested in engineering runs and is now starting to do science observing. In good seeing conditions, the system produces K-band Strehl ratios >0.7 (NGS) and >0.6 (LGS). In LGS mode tip/tilt guiding is achieved with a V~16 natural star anywhere inside a 1 arcminute radius field, which provides about 50% sky coverage. This enables diffraction-limited imaging of regions where few bright guidestars suitable for NGS mode are available. NGS mode requires at least a V~13 guidestar and has a sky coverage of

A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10-m or Lick 3-m, and direct images or AO images are sensitive to a wider field, extending to 10" or 38", depending upon the camera. One of the binary systems -- HD 114762 -- was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system -- Tau Boo -- was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target -- 16 Cyg B -- was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the Tau Boo binary contains an extremely close planet in a tidally-circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU., Comment: 5 Tables, 16 Figures. ApJ, accepted

Progress and results of observations with the Lick Observatory Laser Guide Star Adaptive Optics System are presented. This system is optimized for diffraction-limited imaging in the near infrared, 1-2 micron wavelength bands. We describe our development efforts in a number of component areas including, a redesign of the optical bench layout, the commissioning of a new infrared science camera, and improvements to the software and user interface. There is also an ongoing effort to characterize the system performance with both natural and laser guide stars and to fold this data into a refined system model. Such a model can be used to help plan future observations, for example, predicting the point-spread function as a function of seeing and guide star magnitude.

The resolution of ground-based telescopes is typically limited to {approx}1 second of arc because of the blurring effects of atmospheric turbulence. Adaptive optics (AO) technology senses and corrects for the optical distortions due to turbulence hundreds of times per second using high-speed sensors, computers, deformable mirror, and laser technology. The goal of this project is to make AO systems widely useful astronomical tools providing resolutions up to an order of magnitude better than current, ground-based telescopes. Astronomers at the University of California Lick Observatory at Mt. Hamilton now routinely use the LLNL developed AO system for high resolution imaging of astrophysical objects. We report here on the instrument development progress and on the science observations made with this system during this 3-year ERI project.

During the week of the impacts of Comet Shoemaker-Levy 9 into Jupiter, we used a speckle imaging camera mounted on the Lick Observatory 3 meter Telescope to record a continuous stream of images of the planet. Because the speckle imaging technique compensates for atmospheric blurring, the resulting images were most likely the highest resolution of any taken from the ground. These images compliment the Hubble Space Telescope data by covering time periods when Hubble was not observing Jupiter. We collected full planet 1024 by 1024 pixel CCD images taken 20 per minute for 4 hours per night over 6 nights July 15 to 22. Only a portion of this raw data has been reduced to high resolution images to date.

Adaptive optics on the Keck 10 meter telescope will provide an unprecedented level of capability in highresolution ground-based astronomical imaging [1,2]. The system is designed to provide near diffraction limited imaging performance with Strehl > 0.3 n median Keck seeing of r0 = 25 cm, t0 = 10 msec at 500 nm wavelength. The system will be equipped with a 20 watt sodium laser guide star to provide nearly full sky coverage.

The W.M. Keck Observatory, in collaboration with Lawrence Livermore National Laboratory (LLNL), is currently in the critical design phase of a natural guide star (NGS) and single laser guide star (LGS) adaptive optics (AO) user facility for the Nasmyth platform of the Keck II 10-m telescope.1 Two science instruments will accompany the AO facility: a near infrared camera (NIRC-2) being built at Caltech, and a near infrared spectrometer (NIRSPEC) being built at UCLA. NASA is planning to fund an interferometer between the Keck telescopes which will require a second NGS AO facility on Keck I.