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We present high resolution (~0.1"), very high Strehl ratio (0.97+-0.03) mid-infrared (IR) adaptive optics (AO) images of the AGB star RV Boo utilizing the MMT adaptive secondary AO system. RV Boo was observed at a number of wavelengths over two epochs (9.8 um in May 2003, 8.8, 9.8 and 11.7 um in February 2004) and appeared slightly extended at all wavelengths. While the extension is very slight at 8.8 and 11.7 um data, the extension is somewhat more pronounced at 9.8 um. With such high Strehls we can achieve super-resolutions of 0.1" by deconvolving RV Boo with a point-spread function (PSF) derived from an unresolved star. We tentatively resolve RV Boo into a 0.16" FWHM extension at a position angle of 120 degrees. At a distance of 390(+250)(-100) pc, this corresponds to a FWHM of 60(+40)(-15) AU. We measure a total flux at 9.8 um of 145+-24 Jy for the disk and star. Based on a dust thermal emission model for the observed IR spectral energy distribution and the 9.8 um AO image, we derive a disk dust mass of 1.6x10^-6 Msun and an inclination of 30 to 45 degrees from edge-on. We discuss whether the dust disk observed around RV Boo is an example of the early stages in the formation of asymmetric structure in planetary nebula.

We present the results of mid-infrared nulling interferometric observations of the main-sequence star alpha Lyr (Vega) using the 6.5 m MMT with its adaptive secondary mirror. From the observations at 10.6 microns, we find that there is no resolved emission from the circumstellar environment (at separations greater than 0.8 AU) above 2.1% (3 sigma limit) of the level of the stellar photospheric emission. Thus, we are able to place an upper limit on the density of dust in the inner system of 650 times that of our own solar system's zodiacal cloud. This limit is roughly 2.8 times better than those determined with photometric excess observations such as those by IRAS. Comparison with far-infrared observations by IRAS shows that the density of warm dust in the inner system (< 30 AU) is significantly lower than cold dust at larger separations. We consider two scenarios for grain removal, the sublimation of ice grains and the presence of a planetary mass "sweeper." We find that if sublimation of ice grains is the only removal process, a large fraction (> 80%) of the material in the outer system is ice., 11 pages, 1 figure, Accepted to The Astrophysical Journal Letters

We present the first scientific images obtained with a deformable secondary mirror adaptive optics (AO) system. We utilized the 6.5 m Multiple Mirror Telescope adaptive optics system to produce high-resolution (FWHM ¼ 0>07) near-infrared (1.6 lm) images of the young (� 1 Myr) Orion Trapezium � 1 Ori cluster members. A combination of high spatial resolution and high signal-to-noise ratio allowed the positions of these stars to be measured to within � 0>003 accuracies. We also present slightly lower resolution (FWHM � 0>085) images from Gemini with the Hokupa‘a AO system as well. Including previous speckle data from Weigelt et al., we analyze a 6 yr baseline of high-resolution observations of this cluster. Over this baseline we are sensitive to relative proper motions of only � 0>002 yr � 1 (4.2 km s � 1 at 450 pc). At such sensitivities we detect orbital motion in the very tight � 1 Ori B2-B3 (52 AU separation) and � 1 Ori A1-A2 (94 AU separation) systems. The relative velocity in the � 1 Ori B2-B3 system is 4:2 � 2: 1k m s � 1 . We observe 16:5 � 5: 7k m s � 1 of relative motion in the � 1 Ori A1-A2 system. These velocities are consistent with those independently observed by Schertl et al. with speckle interferometry, giving us confidence that these very small (� 0>002 yr � 1 ) orbital motions are real. All five members of the � 1 Ori B system appear likely gravitationally bound (B2-B3 is moving at � 1.4 km s � 1 in the plane of the sky with respect to B1, where Vesc � 6k m s � 1 for the B group). The very lowest mass member of the � 1 Ori B system (B4) has K 0 � 11:66 and an estimated mass of � 0.2 M� . Very little motion (4 � 15 km s � 1 ) of B4 was detected with respect to B1 or B2; hence, B4 is possibly part of the � 1 Ori B group. We suspect that if this very low mass member is physically associated, it most likely is in an unstable (nonhierarchical) orbital position and will soon be ejected from the group. The � 1 Ori B system appears to be a good example of a star formation ‘‘ minicluster,’’ which may eject the lowest mass members of the cluster in the near future. This ‘‘ ejection ’’ process could play a major role in the formation of low-mass stars and brown dwarfs. Subject headings: binaries: general — instrumentation: adaptive optics — stars: evolution — stars: formation — stars: low-mass, brown dwarfs On-line material: color figures

We utilized the MMT's unique deformable secondary adaptive optics system to produce high-resolution (FWHM=0.3"), very high Strehl mid-infrared (9.8, 11.7 & 18 micron) images of the post-AGB star AC Her. The very high (98+/-2%) Strehls achieved with Mid-IR AO led naturally to an ultra-stable PSF independent of airmass, seeing, or location on the sky. We find no significant difference between AC Her's morphology and our unresolved PSF calibration stars (mu UMa & alpha Her) at 9.8, 11.7, & 18 microns. Our current observations do not confirm any extended Mid-IR structure around AC Her. These observations are in conflict with previously reported Keck (seeing-limited) 11.7 and 18 micron images which suggested the presence of a resolved ~0.6" edge-on circumbinary disk. We conclude that AC Her has no extended Mid-IR structure on scales greater than 0.2" (R

Advances in computing power are improving astronomical imaging by enabling adaptive-optics technology to mitigate atmospheric and other physical variables. Present-day 3.5- to 10-meter telescopes fitted with adaptive optics see farther and with higher resolution than the Hubble Space Telescope. The continuous evolution of ground-based telescope capabilities could make them suitable for applications previously envisioned only for space-based systems.

An adaptive optics system is being built for the 6.5 m Multiple Mirror Telescope (MMT) conversion on Mount Hopkins for diffraction-limited observations in the near-infrared. At the heart of the system is a deformable secondary mirror which introduces corrections to the optical wavefront. By compensating these errors at the telescope's secondary, the system has been optimized for low thermal emissivity and high photon throughput. The scientific productivity of the facility will thereby be enhanced in comparison with a telescope equipped with more conventional adaptive optics. The Large Binocular Telescope under construction on Mount Graham will also use adaptive secondary mirrors. This paper explores the benefit to both facilities in terms of the integration time required to achieve a given signal-to-noise ratio. The gain is found to be substantial in the photometric bands K, L, M, and N.

Laser beams directed into the sky from astronomical observatories to generate guide beacons for adaptive optics image-sharpening systems are a potential hazard to aircraft. Detection systems are needed to sense aircraft and interrupt the laser beam to prevent accidental illumination. We describe here a system designed for this task. A computer examines CCD images of the sky over a wide field of view and uses a motion detection algorithm to find tracks made by aircraft lights. The results of tests, conducted with simultaneous radar coverage from Tucson International Airport, are reported. A test with an actual laser beacon at the Multiple Mirror Telescope in which Mars was used as a simulated aircraft is also described.

Adaptive optics with a sodium resonance laser guide star was used at the Multiple Mirror Telescope (MMT) in 1996 April to image the core of the globular cluster M13 (NGC 6205). A 23'' field was recorded in the Ks band with image resolution of 051, when the uncorrected resolution was 072. Global tilt, not sensed by the laser, was measured from the image motion of a star 35'' from the center of the field. Despite this separation, the star profiles do not vary significantly across the image. Many more stars fainter than Ks = 17.5 can be identified in the corrected image. The 05 imaging capability demonstrated here, though not reaching the performance of existing faster, higher order systems with natural star wave-front sensors, is significant because it can be generally realized for very faint objects under normal observing conditions. This characteristic will carry over to higher order laser-based systems, making them very powerful. Our current 05 resolution is much larger than the diffraction limit for the present MMT array (and its upcoming 6.5 m monolithic replacement) because discontinuities prevent the measurement of phase differences between the array elements. Furthermore, small-scale wave-front aberrations caused by atmospheric and static errors across individual mirrors were not corrected. But our system, by its simultaneous correction of differential slopes derived from the laser beacon and global tilt from the natural guide star, illuminates the principles and sources of error common to all future laser systems.

ARGOS the Advanced Rayleigh guided Ground layer adaptive Optics System for the LBT (Large Binocular Telescope) is built by a German-Italian-American consortium. It will be a seeing reducer correcting the turbulence in the lower atmosphere over a field of 2' radius. In such way we expect to improve the spatial resolution over the seeing of about a factor of two and more and to increase the throughput for spectroscopy accordingly. In its initial implementation, ARGOS will feed the two near-infrared spectrograph and imager - LUCI I and LUCI II. The system consist of six Rayleigh lasers - three per eye of the LBT. The lasers are launched from the back of the adaptive secondary mirror of the LBT. ARGOS has one wavefront sensor unit per primary mirror of the LBT, each of the units with three Shack-Hartmann sensors, which are imaged on one detector. In 2010 and 2011, we already mounted parts of the instrument at the telescope to provide an environment for the main sub-systems. The commissioning of the instrument will start in 2012 in a staged approach. We will give an overview of ARGOS and its goals and report about the status and new challenges we encountered during the building phase. Finally we will give an outlook of the upcoming work, how we will operate it and further possibilities the system enables by design.

A near-infrared adaptive optics system operating at about 50 Hz has been used to control phase errors adaptively between two mirrors of the Multiple Mirror Telescope by stabilizing the position of the interference fringe in the combined unresolved far-field image. The resultant integrated images have angular resolutions of better than 0.1 arcsec and fringe contrasts of more than 0.6. Measurements of wave-front tilt have confirmed the wavelength independence of image motion. These results show that interferometric sensing of phase errors, when combined with a system for sensing the wave-front tilt of the individual telescopes, will provide a means of achieving a stable diffraction-limited focus with segmented telescopes or arrays of telescopes.

We report a multiframe blind deconvolution algorithm that we have developed for imaging through the atmosphere. The algorithm has been parallelized to a significant degree for execution on high-performance computers, with an emphasis on distributed-memory systems so that it can be hosted on commodity clusters. As a result, image restorations can be obtained in seconds to minutes. We have compared and quantified the quality of its image restorations relative to the associated Cramer-Rao lower bounds (when they can be calculated). We describe the algorithm and its parallelization in detail, demonstrate the scalability of its parallelization across distributed-memory computer nodes, discuss the results of comparing sample variances of its output to the associated Cramer-Rao lower bounds, and present image restorations obtained by using data collected with ground-based telescopes.

High-contrast adaptive optics (AO) observations near stars have to contend with the telescope's diffraction halo, a rapidly-changing cloud of residual atmospheric speckles, and a host of faint but persistent quasi-static speckles caused by various imperfections and aberrations. It is these quasi-static speckles that typically limit the detection sensitivity near stars as they are easily confused with faint stellar companions. Since they are coherent with the starlight, it is possible to suppress the quasi-static speckles and other residual diffraction halo over a search region by applying small offsets to the AO system's deformable mirror (DM). Computing the required offsets requires knowledge of the location, brightness, and phase of the speckle relative to the star's PSF core. We present a new wavefront sensing technique for measuring the static halo that uses the randomly-changing residual AO speckles as interferometric probes. Doing this requires simultaneous short-exposure frames from a mid-IR science camera and measurements of the residual closed-loop wavefront using the AO system's wavefront sensor (WFS). These data streams are combined to construct a map of the quasi-static halo's complex amplitude near the bright core of a star's PSF, permitting adaptive halo suppression. Implementing this new WFS and halo-suppression servo requires no new hardware, just new processing applied to the existing AO system. By suppressing the quasi-static speckles, we are left with only the fast speckle noise, which should average to a smooth background.

A multi-laser adaptive optics system, at the 6.5 m MMT telescope, has been undergoing commissioning in preparation for wide-field, partially corrected as well as narrow-field, diffraction limited science observations in the thermal and near infrared. After several delays due to bad weather, we have successfully closed the full high order ground-layer adaptive optics (GLAO) control loop for the first time in February 2008 using five Rayleigh laser guide stars and a single tilt star. Characterization and automated correction of static aberrations such as non-common path errors were addressed in May 2008. Calibration measurements in preparation for laser tomography adaptive optics (LTAO) operation are planned for the fall of 2008 along with the start of shared-risk GLAO science observations. We present the results of GLAO observations with the PISCES imager, a 1 - 2.5 µm camera with a field of view of 110 arc seconds. The status of the remaining GLAO commissioning work is also reviewed. Finally, we present plans for commissioning work to implement the LTAO operating mode of the system.

IMAGES formed by ground-based telescopes are marred by atmospheric 'seeing9. The plane wavefront from an unresolved star is distorted by continually changing turbulent fluctuations in the air's refractive index. Diffraction-limited performance can in principle be recovered through the methods of adaptive optics, in which the instantaneous wavefront shape is sensed and corrected in real-time by deformable optics that cancel the distortion1,2. The highest resolution will be achieved when this technique is applied to multiple-telescope arrays. For such arrays, the biggest errors caused by seeing at infrared wavelengths are the variations in pathlength and wavefront tilt between array elements. We show here that these errors can be derived by an artificial neural network, given only a pair of simultaneous in-focus and out-of-focus images of a reference star formed at the combined focus of all the array elements. We have optimized a neural network appropriate for 2.2-μm wavelength imaging at the Multiple Mirror Telescope in Arizona. Corrections made by moving the beam-combining mirrors will largely recover the diffraction-limited profile, with a resolution of 0.06 arcsec.

In the context of a general wave-mechanical formalism, we derive explicit forms for the Hamiltonian, kinetic energy, and momentum operators for a massive fermion in curved space-time. In the two-spinor representation, the scalar products of state vectors are conserved under the Dirac equation, but the time-development Hamiltonian is in general not Hermitian for a nonstatic metric. A geodesic normal coordinate system provides an economical framework in which to interpret the results. We apply the formalism to a closed Robertson-Walker metric, for which we find the eigenvalues and eigenfunctions of the kinetic energy density. The angular momentum parts turn out to be simpler than in the usual four-spinor representation, and the radial parts involve Jacobi polynomials.

We present a new way to sense atmospheric wave-front phase distortion. Short collimated pulses of laser light at ∼350 nm are projected from a small auxilliary telescope. Rayleigh scattering from each pulse is recorded over a wide range of height through the main telescope aperture in a continuous sequence of fast video frames by a detector conjugate to mid-height. Phase diversity is thus naturally introduced as the pulses approach and pass through focus. We show that an iterative algorithm can extract the phase structure from the recorded images and do so with a much higher signal-to-noise ratio than is possible with existing techniques. If the requirements for real-time data recording and reduction can be met, the new method will address the need for tomographic wave-front sensing at planned 30-m-class telescopes.

A simple scheme is proposed to increase the corrected field of view of a telescope equipped with adaptive optics. The optical system's entrance pupil is projected forward into the atmosphere and is slightly reduced in size. The field in any given direction is then imaged through just a portion of the main aperture, while the full aperture is used to collect light from the reference beacons, which may be either natural stars or laser beacons. The enlargement of the field of view is proportional to the reduction in pupil size and therefore comes at some cost in flux and resolution. A numerical simulation shows that the trade-off is modest and may in many cases be advantageous.

Over the past several years, experiments in adaptive optics involving multiple natural and Rayleigh laser guide stars have been carried out by our group at the 1.5 m Kuiper telescope and the 6.5 m MMT telescope. From open-loop data we have calculated the performance gains anticipated from ground-layer adaptive optics (GLAO) and laser tomography adaptive optics corrections. In July 2007, the GLAO control loop was closed around the focus signal from all five laser guide stars at the MMT, leading to a reduction in the measured focus mode on the laser wavefront sensor by 60%. For the first time, we expect to close the full high order GLAO control loop around the five laser beacons and a tilt star at the MMT in October 2007, where we predict image quality of < 0.2 arc seconds FWHM in K band (λ = 2.2 μm) over a 2 arc minute field. We intend to explore the image quality, stability and sensitivity of GLAO correction as a function of waveband with the science instrument PISCES. PISCES is a 1-2.5 µm imager with a field of view of 110 arc seconds, at a scale of 0.11 arc seconds per pixel. This is well matched to the expected FWHM performance of the GLAO corrected field and will be able to examine PSF non-uniformity and temporal stability across a wide field. FGD.

We present the design of a new high-resolution near-infrared survey camera that will take advantage of the wide corrected field afforded by the 6.5 m MMT's new multi-laser ground-layer adaptive optics (GLAO) system. GLAO technology will correct for turbulence close to the telescope aperture where typically 1/2 to 2/3 of the total atmospheric turbulence lies and is expected to deliver image widths of 0.1-0.2 arc seconds in the near-infrared across a wide range of seeing conditions. The new camera will use a 2 by 2 mosaic of JWST NIRCam detectors, 2048 x 2048 arrays sensitive from 0.6 - 2.5 μm based on Teledyne's HgCdTe HAWAII-2RG detector technology. The camera has a 4 arc minute square field, giving a plate scale of approximately 0.06 arc seconds/pixel, critically sampling the GLAO PSF. In addition, high resolution (0.25 arc seconds or better) multi-object spectroscopy can be supported with cold slit masks inside the dewar; allowing potentially hundreds of spectra to be obtained at once with resolutions of up to 10,000.

The laser guidestar system at the MMT Observatory has produced its first closed loop results and should be producing ground-layer corrected closed loop images within a few months. The LGS system at the MMT is one of few in the world that uses atmospheric Rayleigh scattering from reliable, low-cost lasers, and is unique in its use of a dynamic refocus technique to increase the telescope depth of field for increased return flux. The resulting 10 km depth of field introduces additional constraints on the minimum spot size for the beam projector design. The short exposure spot size as measured at the telescope cassegrain focus is 0.65 arcseconds in 0.59 arcsecond seeing in the visible. Additionally, a method to correct for image motion due to telescope vibrations using accelerometer data has been successfully implemented.

We describe the conceptual design of an advanced laser guide star facility (LGSF) for the Large Binocular Telescope (LBT), to be built in collaboration with the LBT's international partners. The highest priority goal for the facility is the correction of ground-layer turbulence, providing partial seeing compensation in the near IR bands over a 4' field. In the H band, GLAO is projected to improve the median seeing from 0.55" to 0.2". The new facility will build on the LBT's natural guide star AO system, integrated into the telescope with correction by adaptive secondary mirrors, and will draw on Arizona's experience in the construction of the first multi-laser adaptive optics (AO) system at the 6.5 m MMT. The LGSF will use four Rayleigh beacons at 532 nm, projected to an altitude of 25 km, on each of the two 8.4 m component telescopes. Initial use of the system for ground layer correction will deliver image quality well matched to the LBT's two LUCIFER near IR instruments. They will be used for direct imaging over a 4'×4' field and will offer a unique capability in high resolution multi-object spectroscopy. The LGSF is designed to include long-term upgrade paths. Coherent imaging at the combined focus of the two apertures will be exploited by the LBT Interferometer in the thermal IR. Using the same launch optics, an axial sodium or Rayleigh beacon can be added to each constellation, for tomographic wavefront reconstruction and diffraction limited imaging over the usual isoplanatic patch. In the longer term, a second DM conjugated to high altitude is foreseen for the LBT's LINC-NIRVANA instrument, which would extend the coherent diffraction-limited field to an arcminute in diameter with multi-conjugate AO.

Laser beams for guide star generation are a potential hazard for aircraft. At the MMT telescope located on Mt. Hopkins in Southern Arizona, a constellation of five Rayleigh guide stars is created with a total of 25 W of projected power at 532 nm wavelength. We report operational results from an automatic system deployed at the MMT that is designed to detect aircraft and shut down the lasers if a collision with the beams appears likely. The system, building on a previous prototype, uses a wide-angle CCD camera mounted with a minimally unobstructed view to the optical support structure at the top of the telescope. A computer program reads the camera once every two seconds and calculates the difference between adjacent image pairs. The anti-collision beacons required on all aircraft by the Federal Aviation Administration appear as streaks in the field. If an airplane is detected, it is located in the field relative to the laser beam and its path is projected. If aircraft are detected near or appear that they will approach the beam, the laser's safety shutter is closed and warning messages are sent to the laser operator. Failsafe operation is assured by a "heart beat" signal continuously sent from the detection system to the laser controller, and by the fact that the safety shutter must be energized to open. In the event of a power failure, the system must be manually reset by the Laser Safety Officer before the laser beam can again be propagated.

An accurate and timely model of the atmospheric turbulence profile is an important input into the construction of tomographic reconstructors for laser tomography adaptive optics (LTAO) and multi-conjugate adaptive optics (MCAO) using multiple guide stars. We report on a technique for estimating the turbulence profile using the correlations between the modal reconstructions of open-loop wavefront sensor (WFS) measurements from natural or laser guide stars. Laser guide stars can provide an estimate of the turbulence profile along the line of sight to any suitable science target. Open-loop WFS measurements, acquired at the MMT telescope, have been analyzed to recover an estimate of the C2n profile. This open-loop WFS data can be used to yield turbulence estimates in near real-time, which can be used to update the tomographic reconstructor prior to closed-loop operation. This method can also be applied in closed-loop, using telemetry data already captured by multi-guide star adaptive optics (AO) systems, by computing estimates of the wavefront modal covariances from the closed-loop WFS residual error signals and the deformable mirror (DM) actuator positions. This will be of particular value when implemented with accurate position feedback from the AO system's DMs, rather than the input actuator commands, as is possible with an adaptive secondary mirror. We plan the first tests of the technique with the MMT's adaptive secondary and five Rayleigh laser guide stars.

We introduce adaptive optics as a technique to improve images taken by ground-based telescopes through a turbulent blurring atmosphere. Adaptive optics rapidly senses the wavefront distortion referenced to either a natural or laser guidestar, and then applies an equal but opposite profile to an adaptive mirror. In this paper, we summarize the application of neural networks in adaptive optics. First, we report previous work on employing multi-layer perceptron neural networks and back-propagation to learn how to sense and reconstruct the wavefront. Second, we show how neural networks can be used to predict the wavefront, and compare the neural networks’ predictive power in the presence of noise to that of linear networks also trained with back-propagation. In our simulations, we find that the linear network predictors train faster, they have lower residual phase variance, and they are much more tolerant to noise than the non-linear neural network predictors, though both offer improvement over no prediction. We conclude with comments on how neural networks may evolve over the next few years as adaptive optics becomes a more routine tool on the new large astronomical telescopes.

Observational tests of ground layer wavefront recovery have been made in open loop using a constellation of four natural guide stars at the 1.55 m Kuiper telescope in Arizona. Such tests explore the effectiveness of wide-field seeing improvement by correction of low-lying atmospheric turbulence with ground-layer adaptive optics (GLAO). The wavefronts from the four stars were measured simultaneously on a Shack-Hartmann wavefront sensor (WFS). The WFS placed a 5 x 5 array of square subapertures across the pupil of the telescope, allowing for wavefront reconstruction up to the fifth radial Zernike order. We find that the wavefront aberration in each star can be roughly halved by subtracting the average of the wavefronts from the other three stars. Wavefront correction on this basis leads to a reduction in width of the seeing-limited stellar image by up to a factor of 3, with image sharpening effective from the visible to near infrared wavelengths over a field of at least 2 arc minutes. We conclude that GLAO correction will be a valuable tool that can increase resolution and spectrographic throughput across a broad range of seeing-limited observations., 25 pages, 8 figures, to be published in Astrophys. J

Abundances of material components in objects are usually computed using techniques such as linear spectral unmixing on individual pixels captured on hyperspectral imaging devices. The effectiveness of these algorithms usually depends on how distinct the spectral signatures in the libraries used in them are. This can be measured by SVD or Least Squares based figures of merit such as the condition number of the matrix consisting of the library signatures. However, it must be noted that each library signature usually is the mean of a number of signatures representing that material, or class of objects. This aspect of how individual library spectral signatures vary in real-world situations needs to be addressed in order to more accurately assess linear unmixing techniques. These same considerations also goes for signature libraries transformed into new ones by wavelet or other transforms. Figures of merit incorporating variations within each library signature (which more accurately reflects real measurements) will be implemented and compared with other figures of merit not taking these variations into account.

We describe a simple and cost-effective concept for implementing a Ground Layer Adaptive Optics (GLAO) system on Gemini that will feed all instruments mounted at the Cassegrain focus. The design concept can provide a GLAO correction to any of the current or future seeing-limited optical or near-infrared Gemini instruments. The GLAO design uses an adaptive secondary mirror and provides a significant upgrade to the current telescope acquisition-and-guide system while reusing and building upon the existing telescope facilities and infrastructure. This paper discusses the overall design of the GLAO system including optics, opto-mechanics, laser guide star facilities, natural and laser guide stars wavefront sensors. Such a GLAO system will improve the efficiency of essentially all observations with Gemini and also will help with scheduling since it virtually eliminates poor seeing., Ground-based and Airborne Instrumentation for Astronomy, May 24, 2006, Orlando, Florida, United States, Series: Proceedings of SPIE; no. 6269

The MMT's five Rayleigh laser guide star system has successfully demonstrated open loop wavefront sensing for both ground-layer and laser tomography adaptive optics (AO). Closed loop correction is expected for the first time in the autumn of 2006. The program is moving into its second phase: construction of a permanent facility to feed AO instruments now used with the telescope's existing natural star AO system. The new facility will preserve the thermal cleanliness afforded by the system's adaptive secondary mirror. With the present laser power of 4 W in each of the Rayleigh beacons, we will first offer ground-layer correction over a 2 arcmin field in J, H, and K bands, with expected image quality routinely 0.2 arcsec or better. Later, we will also offer imaging and spectroscopy from 1.5 to 4.8 μm with a tomographically corrected diffraction limited beam. The development of these techniques will lead to a facility all-sky capability at the MMT for both ground-layer and diffraction-limited imaging, and will be a critical advance in the tools necessary for extremely large telescopes of the future, particularly the Giant Magellan Telescope. We describe the present state of system development, planned progress to completion, and highlight the early scientific applications.

SPIE Astronomical Telescopes + Instrumentation, 2006, Orlando, Florida , United States, Series: Proceedings of SPIE; no. 6272

The Giant Magellan Telescope, with seven 8.4 meter primary mirrors, is taking shape as one of the most powerful telescopes of the next generation. We describe a conceptual design for a powerful 0.85 to 2.50 μm imaging spectrograph that addresses a 7' by 7' field of view for imaging and a 5' by 7' field of view for spectroscopy at the GMT's f/8 Gregorian focus. The all-refractive optical design presses the limits of available lens blank diameters, but delivers excellent images (~0.15" 80% encircled energy) with just four collimator elements and five camera elements. The collimated beam diameter is 300 mm, and the detector is a 6K by 10K array. The spectrograph will use interchangeable slit masks, and an assortment of VPH and conventional surface relief gratings. Each of the entire J, H, or K bands can be observed with a resolution of 3000. The scientific potential of ground layer adaptive optics (GLAO) using a constellation of sodium laser guide stars appears to be very high in the near infrared. Simulations suggest that 0.2" FWHM images may be achieved across the entire 7' by 7' field of view of the spectrograph. We describe the design of the GLAO system with a versatile opto-mechanical design that allows rapid changeover between GLAO and seeing-limited observations.

The Giant Magellan Telescope (GMT) includes adaptive optics (AO) as an integral component of its design. Planned scientific applications of AO span an enormous parameter space: wavelengths from 1 to 25 μm, fields of view from 1 arcsec to 8 arcmin, and contrast ratio as high as 10 9 . The integrated systems are designed about common core elements. The telescope's Gregorian adaptive secondary mirror, with seven segments matched to the primary mirror segments, will be used for wavefront correction in all AO modes, providing for high throughput and very low background in the thermal infrared. First light with AO will use wavefront reconstruction from a constellation of six continuous-wave sodium laser guide stars to provide ground-layer correction over 8 arcmin and diffraction-limited correction of small fields. Natural guide stars will be used for classical AO and high contrast imaging. The AO system is configured to feed both the initial instrument suite and ports for future expansion.

Abundances of material components in objects are usually computed using techniques such as linear spectral unmixing on individual pixels captured on hyperspectral imaging devices. However, algorithms such as unmixing have many flaws, some due to implementation, and others due to improper choices of the spectral library used in the unmixing (as well as classification). There may exist other methods for extraction of this hyperspectral abundance information. We propose the development of spatial ground truth data from which various unmixing algorithm analyses can be evaluated. This may be done by implementing a three-dimensional hyperpspectral discrete wavelet transform (HSDWT) with a low-complexity lifting method using the Haar basis. Spectral unmixing, or similar algorithms can then be evaluated, and their effectiveness can be measured by how well or poorly the spatial and spectral characteristics of the target are reproduced at full resolution (which becomes single object classification by pixel).

Using five independent analytic and Monte Carlo simulation codes, we have studied the performance of wide field ground layer adaptive optics (GLAO), which can use a single, relatively low order deformable mirror to correct the wavefront errors from the lowest altitude turbulence. GLAO concentrates more light from a point source in a smaller area on the science detector, but unlike traditional adaptive optics, images do not become diffraction-limited. Rather the GLAO point spread function (PSF) has the same functional form as a seeing-limited PSF, and can be characterized by familiar performance metrics such as Full-Width Half-Max (FWHM). The FWHM of a GLAO PSF is reduced by 0.1" or more for optical and near-infrared wavelengths over different atmospheric conditions. For the Cerro Pachon atmospheric model this correction is even greater when the image quality is worst, which effectively eliminates "bad-seeing" nights; the best seeing-limited image quality, available only 20% of the time, can be achieved 60 to 80% of the time with GLAO. This concentration of energy in the PSF will reduce required exposure times and improve the efficiency of an observatory up to 30 to 40%. These performance gains are relatively insensitive to a number of trades including the exact field of view of a wide field GLAO system, the conjugate altitude and actuator density of the deformable mirror, and the number and configuration of the guide stars., Comment: 16 pages, 19 figures, accepted for publication in PASP

The world’s first adaptive secondary has been commissioned at the 6.5m MMT. Early science results suggests that it is unique and highly productive. Nearly diffraction-limited 0.07” H band images have been obtained of the Trapezium core [Close et al. 2003b]. Moreover, an adaptive secondary makes low emissivity Mid-IR (8-20 micron) AO science possible for the first time. We have obtained the first Mid-IR AO results with Strehls of ∼100% from 8-20 microns. The very high PSF stability at such Strehls has allowed us to rule out any extended (> 0.2 ) structure around the post-AGB stars AC Her and Alpha Her [Close et al. 2003c]. In addition, Biller et al. (2003) has used this PSF stability to obtain super-resolutions through deconvolution. The resulting 0.1” images of the AGB star RV Boo detects a dust disk for the first time [Biller et al. 2003].

Experiments have been carried out at the MMT telescope to validate ground layer wavefront reconstruction using five dynamically refocused Rayleigh laser beacons. Here we quantify the wavefront improvement expected from ground layer adaptive optics correction.

We outline ongoing work at the MMT telescope to develop altitude-conjugated adaptive optics using a constellation of laser guide stars. We describe how the new techniques will be applied to the planned Giant Magellan Telescope.

Adaptive optics to correct current telescopes over wide fields, or future very large telescopes over even narrow fields, will require real-time wavefront measurements made with a constellation of laser beacons. Here we report the first such measurements, made at the 6.5 m MMT with five Rayleigh beacons in a 2 arcmin pentagon. Each beacon is made with a pulsed beam at 532 nm, of 4 W at the exit pupil of the projector. The return is range-gated from 20-29 km and recorded at 53 Hz by a 36-element Shack-Hartmann sensor. Wavefronts derived from the beacons are compared with simultaneous wavefronts obtained for individual natural stars within or near the constellation. Observations were made in seeing averaging 1.0 arcsec with 2/3 of the aberration measured to be from a ground layer of mean height 380 m. Under these conditions, subtraction of the simple instantaneous average of the five beacon wavefronts from the stellar wavefronts yielded a 40% rms reduction in the measured modes of the distortion over a 2 arcmin field. We discuss the use of multiple Rayleigh beacons as an alternative to single sodium beacons on 8 m telescopes, and the impact of the new work on the design of a multi-sodium beacon system for the 25 m Giant Magellan Telescope., Comment: 25 pages, 7 figures, uses aastex.cls, to be published in the Astrophys. J

We investigate the disk harmonic basis functions as an alternative to the Zernike basis functions and their application to fast, analytic adaptive optics simulations which require a large number of degrees of freedom.

Simultaneous wavefront measurements are planned at the 6.5 m MMT telescope of five dynamically refocused Rayleigh laser beacons (RLGS) and a bright natural star to demonstrate tomographic wavefront reconstruction. In this paper, we summarize preliminary data recorded from the five laser beacons during the first telescope run at the MMT in June 2004. Beam projection is from behind the secondary of the MMT to form a regular pentagon of beacons on the sky with a radius of 60 arcseconds around the natural star. Beacon images are recorded over a range gate from 20 to 30 km, with dynamic refocus optics in the focal plane to remove perspective elongation (Stalcup, et. al., these proceedings). Separate externally synchronized Shack-Hartmann sensors record wavefront measurements of the beacons and the star, which will yield the first 33 Zernike modes from each wavefront measurement. A linear tomographic reconstructor, implemented as a matrix multiplication of the combined Zernike modal amplitudes from all five RLGS, has been computed to estimate contributions to the atmospheric aberration in two layers at 0 and 6 km. To validate the tomographic approach, the wavefront of the natural star will be predicted by computing the sum of the aberration in the direction of the star, and the prediction compared to simultaneous measurements recorded from the star directly.

A demonstration of tomographic wavefront sensing has been designed, fabricated, and tested. The last of the initial testing of the dynamic refocus system at the 61" telescope on Mt. Bigelow, Arizona is presented, along with the first results from the system after its transfer to the 6.5 m MMT on Mt. Hopkins, Arizona. This system consists of a laser beam projector, and a wavefront sensor at the telescope's Cassegrain focus. The projector transmits 5 pulsed 532 nm beams in a regular pentagon of 2 arcminutes diameter from behind the telescope's secondary mirror that in good seeing can yield sub-arcsecond beacons over a 20-30 km altitude range. The wavefront sensor incorporates a dynamic refocus unit to track each returning laser pulse, and a multiple laser beacon Shack-Hartmann wavefront sensor using a novel substitute for the traditional lenslet array. A natural guide star wavefront sensor was also fielded to collect ground-truth data to compare with wavefronts reconstructed from the laser wavefront sensor measurements. All of the subsystems were shown to work, but bad weather ended the testing before the final data could be collected.

We plan to take advantage of the unprecedented combination of low thermal background and high resolution provided by the 6.5m MMT's adaptive secondary mirror, to target the 3-5 micron atmospheric window where giant exoplanets are expected to be anomalously bright. We are in the process of building a 3-5 micron camera that we will use to carry out a survey to characterize the prevalence and distribution of giant planets around nearby, Sun-like stars. Sensitivity estimates show that for a 1 Gyr old G0V primary at 10 pc, we expect to detect 5 MJupiter and 15 MJupiter exoplanets at angular separations greater than 0.45-2.1" and 0.2-1.2" respectively. Monte Carlo simulations based on these sensitivity estimates and a sample of 80 young (

Observations have been made at the Steward Observatory 1.55 m telescope of a four-star asterism in the constellation Serpens Cauda, using a Shack-Hartmann wavefront sensor. The stars are all within a 2 arcminute field, and range in apparent brightness from m v of 9.4 to 10.6. The instrument placed a 5 × 5 array of square subapertures across the pupil of the telescope, and had sufficient field of view to allow wavefront data to be recorded from all four stars simultaneously. Snapshots at 1/30 s exposure time were recorded, with no temporal coherence between exposures. We have reconstructed the first 20 Zernike modes from the slope data for each star. In a preliminary analysis, we show that the wavefront aberration in each star can be roughly halved by subtracting the average of the wavefronts from the other three stars. The averages represent estimates of the aberration introduced by the lowest few hundred meters of the atmosphere, so the result provides an early indication of the potential for image sharpening by compensation of boundary layer turbulence. Keywords: Wavefront sensors, adaptive optics, ground layer adaptive optics

Adaptive optics will play a crucial role in achieving the full potential of the next generation of large diameter telescopes. In this paper, we present an optical design for a multi-conjugate adaptive optics system for the Giant Magellan Telescope, a 25.7 m telescope with a primary mirror consisting of seven 8.4 m segments. The tri-conjugate MCAO optics is based on adaptive secondary technology developed for the MMT telescope and incorporates dynamic refocus optics for the laser guide star wavefront sensors. We use the results of analytic (non-Monte-Carlo) numerical simulations to determine the optimal configuration of deformable mirrors as well as laser and natural guide stars. The simulation results are extended to include and quantify the effects of wavefront sensor and control loop delay noise as well as dynamic refocus and fitting error on the expected system performance and sky coverage.

The adaptive secondary for the MMT is the first mirror of its kind. It was designed to allow the application of wavefront corrections (including tip-tilt) directly at the secondary mirror location. Among the advantages of such a choice for adaptive optics operation are higher throughput, lower emissivity, and simpler optical setup. Furthermore, this specific implementation provides capabilities that are not found in most correctors including internal position feedback, large stroke (to allow chopping) and provision for absolute position calibration. The mirror has now been used at the MMT during several runs where it has performed reliably. In this paper we discuss the mirror operation and AO performance achieved during these runs in which the adaptive secondary has been operating in conjunction with a Shack-Hartmann wavefront sensor as part of the MMT adaptive optics system. In particular we mention a residual mirror position error due to wind buffeting and other errors of ≈ 15 nm rms surface and a stable closed loop operation with a 0dB point of the error transfer function in the range 20-30 Hz limited mainly by the wavefront sensor maximum frame rate. Because of the location of the adaptive secondary with respect to the wavefront sensor camera, reimaging optics are required in order to perform the optical interaction matrix measurements needed to run the AO loop. This optical setup has been used in the lab but not replicated at the telescope so far. We will discuss the effects of the lack of such an internal calibration on the AO loop performances and a possible alternative to the lab calibration technique that uses directly light from sky objects.

Radial velocity studies represent the most successful method to date for the detection of extrasolar planets. Although radial velocity (v r ) measurement precision of 3 m s -1 is routinely achieved in some programs, it is important to understand and minimize sources of experimental error. Furthermore, velocity variations resulting from astrophysical processes contribute to velocity errors, and must be removed if precision is to be further improved. The use of spectrographs with telescopes having high order adaptive optics (AO) systems offers the possibility of achieving near diffraction-limited very high spectral resolution at visible wavelengths on ground-based telescopes. The small stellar image diameters obtained with adaptively corrected systems allow high resolution without a large loss of light at the spectrograph entrance aperture. The Adaptively Corrected Echelle Spectrograph (ACES), designed at Steward Observatory for a spectral resolution R ~ 200,000, couples the telescope image to the instrument with an 8-10μm diameter near single-mode optical fiber. The shorter effective slit permits the placement of more echelle orders on the detector after cross dispersion, with a correspondingly greater wavelength coverage per exposure. This simultaneous high resolution and large wavelength coverage can be used to improve the precision of radial velocity studies by improving wavelength calibration, reducing dataset internal errors, and permitting better characterization and removal of effects intrinsic to the stars themselves.

The use of spectrographs with telescopes having high order adaptive optics (AO) systems offers the possibility of achieving near diffraction-limited spectral resolution on ground-based telescopes, as well as important advantages for instrument design. The small stellar image diameters obtained with adaptively corrected systems allow high resolution without a large loss of light at the spectrograph entrance slit, as well as greater spectral coverage per exposure. The adaptively corrected echelle spectrograph (ACES), designed at Steward Observatory for a spectral resolution R ≈ 200,000, couples the telescope pupil to the instrument with a 10 mm diameter near single-mode optical fiber. Initial observations at the 2.5m telescope on Mt. Wilson validated the concept of achieving high spectral resolution with an adaptively corrected telescope and fiber coupled spectrograph. However the transmission of multiple modes in the fiber lead to a wavelength-dependent variation in illumination that made flat fielding impossible. In this paper we describe instrument design improvements, the installation and testing of a new CCD detector, and testing aimed at understanding and eliminating the fiber-related transmission problems to permit science quality imaging.