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LBT at the Astronomical Telescopes and Instrumentation 2000 Meeting

27-31 March 2000, Munich, Germany
Sponsored by the SPIE, The International Society for Optical Engineering

Abstracts and LBT-related papers:

Conference 4004: Telescope Structures, Enclosures, Controls,
Assembly/Integration/Validation, and Commissioning

[4004-07] The Large Binocular Telescope Project

J. M. Hill, The University of Arizona
Piero Salinari, Osservatorio Astrofisico di Arcetri

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, and Ohio. Arizona includes astronomers at The University of Arizona, Arizona State University and Northern Arizona University. Germany is represented by the LBT Beteiligungsgesellschaft which is composed of Max-Planck-Institut für Astronomie in Heidelberg, Landessterwarte Heidelberg, Max-Planck-Institut für Radioastronomie in Bonn, Max-Planck-Institut für extraterrestrische Physik in Munich and Leibniz Institute for Astrophysics Potsdam. The Italian astronomical community is represented by the Osservatorio Astrofisico di Arcetri in Florence. Partners at individual institutions include The Ohio State University in Columbus, The University of Notre Dame and Research Corporation in Tucson. The second of two 8.4m borosilicate honeycomb primary mirrors for LBT is being cast at the Steward Observatory Mirror Lab this year. The baseline optical configuration of LBT includes adaptive infrared secondaries of a Gregorian design. The F/15 secondaries are undersized to provide a low thermal background focal plane which is unvignetted over a 4 arcminute diameter field-of-view. The interferometric focus combining the light from the two 8.4 meter primaries will reimage the two folded Gregorian focal planes to three central locations. The telescope elevation structure accommodates swing arm spiders which allow rapid interchange of the various secondary and tertiary mirrors as well as prime focus cameras. Maximum stiffness and minimal thermal disturbance were important drivers for the design of the telescope in order to provide the best possible images for interferometric observations. The telescope structure accommodates installation of a vacuum bell jar for aluminizing the primary mirrors in-situ on the telescope. The telescope structure is being fabricated in Italy by Ansaldo Energia S.p.A. in Milan. After pre-erection in the factory, it will be shipped to Arizona toward the end of the year. The enclosure is being built on Mt. Graham under the auspices of Hart Construction Management Services of Safford, Arizona. The enclosure will be completed later this year and ready for telescope installation.

pp. 36-46

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[4004-16] Nearly completed Large Binocular Telescope facility yields many lessons learned

J. H. Slagle, J. M. Hill, W. B. Davison, Steward Observatory/Univ. of Arizona
W. Hart, Hart Construction Management Services, Inc.
J. U. Teran, M3 Engineering & Technology Corp.

The use of a team approach by contractors, engineers and management to build the Large Binocular Telescope (LBT) has been successful in maintaining quality construction at a reasonable price. No matter how efficient the team, the building of a 16 story building, with a totally unique design, and on just 1.2 acres of land does present formidable problems. This paper will present the current status of the LBT construction on Mt. Graham and how the team approach has continued to be successful in providing quality solutions on a timely basis while keeping the costs of construction to a minimum. The paper will discuss many issues that project managers must plan for when undertaking new and unique designs and what steps managers can take to avoid costly delays.

pp. 446-456

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[4004-19] Large Binocular Telescope M3 units design

D. Gallieni, ADS International s.r.l. (Italy)
J. M. Hill, Steward Observatory/Univ. of Arizona
P. Salinari, Osservatorio Astrofisico di Arcetri (Italy)
W. B. Davison, Steward Observatory/Univ. of Arizona

We report on the design of the two tertiary mirrors of the Large Binocular Telescope. The tertiary mirrors are flat octagonal shaped 540x640 mm Hextek honeycombs made of Schott borosilicate. Each mirror cell is mounted on three linear actuators for the active control of the mirror pointing and for the adjustment of the telescope optical path length. Each tertiary mirror unit embeds a rotator stage to point at four different instrument stations on the telescope. Particular effort is devoted to the optimization of the honeycomb mirror support system to minimize the optical surface RMS deformation at the different mirror attitudes.


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[4004-23] Large Binocular Telescope erection

L. Miglietta, Astrophysical Observatory of Arcetri (Italy)
D. Gallieni, E. Anaclerio, ADS International s.r.l. (Italy)
G. Castelli, G. Tassa Din, P. Villa, Ansaldo Energia S.p.A. (Italy)
G. Marchiori, A. Zanon, European Industrial Engineering s.r.l. (Italy)
R. Tomelleri, P. Rossettini, Tomelleri s.r.l. (Italy)

The Large Binocular Telescope is currently in pre-erection at the Ansaldo Energia workshop in Milan. Since late 1998 the manufacturing of the Azimuth and Elevation structures has been taken place in North Italy along with the main auxiliary equipment, and since September 1999, the Azimuth Ring have been assembled and aligned on the new concrete foundation poured months before in the Ansaldo area. The pre-erection activity in Italy will take some months more from now and the final acceptance tests are scheduled for July 2000; after that the whole telescope will be disassembled and shipped to Mt. Graham. In this paper, the Authors, part of some industrial companies and public institutes main character in this scientific and technical challenge, briefly describe the manufacturing and the machining processes of the telescope components, the results and the procedures adopted of the pre-assembling process as test bench for the final erection in Arizona.

pp. 115-126

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[4004-25] The Structural Design of the Co-Rotating Enclosure for the Large Binocular Telescope

D. H. Neff, J. U. Teran, E. A. Hileman, H. J. Lewsley, M3 Engineering & Technology Corp.

The Large Binocular Telescope (LBT) under construction on Mt. Graham.

pp. 135-142


[4004-32] Design and realization of ancillary control loops for the MMT adaptive optics system

G. Z. Angeli, B. C. Fitz-Patrick, M. Lloyd-Hart, Steward Observatory/Univ. of Arizona

The adaptive optics system of the Multiple Mirror Telescope is going to realize a high speed (1 kHz bandwidth) and high order (336 actuators) wavefront correction. However, to achieve the required 0.08 arcsec pointing stability the focal point of the Shack-Hartman wavefront sensor must be kept aligned to the Cassegrain focus better than 10 mm in spite of the non-common path tip/tilt error due to mechanical and thermal deformation of the telescope structure. The wave-front sensor must also be rotated with high precision to keep it aligned with the deformable secondary mirror in spite of the parallactic angle correction of the telescope. Our approach is to use a feed-forward loop to eliminate the adverse effect of deformation. A fast, deterministic field bus is applied to interconnect the actuators, sensors and computers. The bandwidth (500kbs) and latency (less than 1 ms) of the DeviceNet serial bus is adequate to support our distributed control system. The field bus architecture simplifies and standardizes the control software as well as improves the reliability of the electronics by reducing the wiring.

pp. 202-211

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Conference 4006: Interferometry in Optical Astronomy

[4006-37] Nulling interferometric beam combiner utilizing dielectric plates: experimental results in the visible broadband
R. M. Morgan, J. H. Burge, N. J. Woolf, Univ. of Arizona

The heart of TPF is the nulling beam combiner: a set of optics that combines the light from various collecting telescopes to produce a central destructive fringe rather than the natural constructive fringe.

pp. 340-348


[4006-38] BLINC: a testbed for nulling interferometry in the thermal infrared

P. M. Hinz, J. R. P. Angel, N. J. Woolf, W. F. Hoffmann, D. W. McCarthy, Jr., Steward Observatory/Univ. of Arizona

A key technology in NASA's plans for a Terrestrial Planet Finder (TPF) is nulling interferometry in the thermal infrared.

pp. 349-353


[4006-61] Tomographic methods for the restoration of LBT images
M. Bertero and P. Boccacci, Univ. di Genova (Italy) S. Correia, A. Richichi, Osservatorio Astrofisico di Arcetri (Italy)

The Large Binocular Telescope (LBT) has been designed for providing images with high sensitivity and resolution by means of optical/infrared interferometry. It will require specific methods for data reduction since the image of an astronomical object will be obtained from a set of interferometric images corresponding to different orientations of the baseline. In this paper we first stress an interesting analogy between the images of LBT and the projections in Computed tomography (CT). Next we use this analogy for extending to LBT some iterative restoration methods developed for CT, such as ML-EM (Maximum Likelihood -Expectation Maximization), its accelerated version OS-EM (Ordered Subset - Expectation Maximization) and the improved version RAMLA (Row-Action Maximum Likelihood Algorithm). These iterative methods approximate solutions of the Maximum Likelihood problem in the case of Poisson noise. We also consider iterative methods which have been proposed for solving the same problem in the case of Gaussian noise, in particular the Iterative Space Recostruction Algortithm (ISRA) and the Projected Landweber (PL) method. All these methods are implemented and tested by means of same simulated LBT images.

pp. 514-522

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[4006-79] Large Binocular Telescope image restoration using simulated adaptively corrected point-spread functions

S. Correia, M. Carbillet, A. Richichi, Osservatorio Astrofisico di Arcetri (Italy)
M. Bertero and P. Boccacci, Univ. di Genova (Italy)
In this paper we present simulations of Large Binocular Telescope (LBT) image reconstruction carried out on different types of scientific object. The set of Adaptive Optics-corrected point-spread functions (AO-corrected PSFs) used was generated by means of the Code for Adaptive Optics System (CAOS 2.0). For clarity only one restoration method was applied to the simulated data, namely the extension of the Lucy-Richardson (LR) algorithm, also called ML-EM (Maximum Likelihood - Expectation Maximization). When possible we evaluated the quality of the restorations obtained both by astrometric and photometric analysis. By comparison with results obtained using analytical PSFs, we point out the effect induced by the AO correction on the precision of the retrieved astrometric and photometric parameters or on the morphology of the reconstructed object.

pp. 650-658

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[4006-80] Cryogenic Beamcombiner for Very Low Background, 2-20 Micron Interferometry on the 22.8m Large Binocular Telescope

D. W. McCarthy, E. M. Sabatke, R. J. Sarlot, P. M. Hinz, and J. H. Burge, The University of Arizona

Interferometry with the 22.8m Large Binocular Telescope (LBT) will be a uniquely powerful tool in the thermal infrared (2-20 microns) because of the unusual combination of low thermal emissivity, high spatial resolution, broad (u,v)-plane coverage, and high photometric sensitivity. Equipped with a central cooled beamcombiner, the LBT is capable of both spatial interferometry and nulling interferometry. Adaptive secondaries, as well as a common mount for the two 8.4m primary mirrors, permit beam combination after only three warm reflections. We present an all-reflective optical design for the beamcombiner which satisfies the requirement of large interferometric fields for Fizeau- style imaging as well as the low thermal background and achromaticity required for nulling. The beamcombiner operates over a wavelength range of 2-20 microns to feed a variety of interchangeable cameras and spectrographs. Integrated tip-tilt and pathlength (phase) sensors permit accurate control of these errors caused both by atmospheric turbulence and telescope flexure. With nulling interferometry the LBT will be unsurpassed in its sensitivity to circumstellar environments. At 11 microns the instrument will be sensitive to zodiacal dust down to solar level around nearby stars. At 4 microns planets as small as Jupiter and younger than one billion years will be detectable.

pp. 659-672

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[4006-82] LINC: a near-infrared beam combiner for the Large Binocular Telescope

T. M. Herbst, H. W. Rix, P. Bizenberger, and M. Ollivier, Max-Planck-Institut für Astronomie (Germany)

The Large Binocular Telescope (LBT), currently under construction on Mount Graham in Arizona, will be the world's largest single telescope when it is completed in 2003. With its dual, 8.4 meter diameter primary mirrors and a maximum baseline of 23 meters, LBT will provide interferometrists an unprecedented combination of large collecting area, wide field of view, and high spatial resolution.

To take advantage of this, several concepts for beam-combiners and associated instrumentation are under development. We review the current concepts for a beam-combiner to operate in the near-infrared, specifically those proposed by the MPIA in Heidelberg and the Arcetri Observatory in Florence, and emphasize the need for a wide collaboration in the design and realization of this project.

Because the two mirrors of the telescope have a common mount, the entrance pupil geometry of the interferometer does not vary for different pointing directions. This makes it relatively easy to construct an instrument that preserves this geometry, allowing image-plane or "Fizeau" interferometry. Our simulations suggest that we will be able to achieve true imagery with ~10 mas resolution over a field of several tens of arcseconds in diameter with excellent sensitivity (for example, S/N of 10 on a 20 nJy point source in 3 hours at K').

Such performance enables a variety of fundamental, new science programs. For example, we anticipate pushing the supernova cosmology studies to beyond redshift 3, studying the time evolution of stellar jets, and detecting Jupiter-mass planets around stars within 100 pc due to their reflex, astrometric wobble. Building this instrument represents a significant challenge, however. The prototype instrument will likely be uncooled, but we are examining options for eventually having a fully cryogenic beam combiner. Ultimately, an additional, internal adaptive corrector may increase the Strehl ratio over a larger field of view and allow operation at wavelengths shorter than 1 micron.

pp. 673-680

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[4006-128] Second-order phase theory in multiple aperture systems

E. M. Sabatke and J. M. Sasian, University of Arizona

We establish the groundwork for a phase theory applicable to multiple-aperture systems. We examine the phase behaviour of a reference system

pp. 1083-1089


[4006-132] Considerations about the differential piston for adaptive optics interferometry

B. Femenia, M. Carbillet, S. Esposito, A. Riccardi, Osservatorio Astrofisico di Arcetri (Italy)

The contribution extends a previous work where the concept of piston angular anisoplanatism was introduced and the issue of sky coverage for large ground-based optical interferometers was raised. We obtain expressions ......

pp. 1116-1127


Conference 4007: Adaptive Optical Systems Technology

[4007-01] The adaptive secondary mirror for the 6.5m conversion of the Multiple Mirror Telescope: latest laboratory results from the P36 prototype
A. Riccardi, G. Brusa, V. Biliotti, C. Del Vecchio, P. Salinari, P. Stefanini, Osservatorio Astrofisico di Arcetri (Italy)
P. Mantegazza, Politecnico di Milano (Italy)
R. Biasi, M. Andrighettoni, MicroGate S.r.L. (Italy)
C. Franchini, Media Lario S.r.L. (Italy)
D. Gallieni, ADS International S.r.L. (Italy)
M. Lloyd-Hart, P. C. McGuire, S. M. Miller, H. M. Martin, Steward Observatory/Univ. of Arizona

The 336-actuator adaptive secondary unit (MMT336) for the new MMT is being assembled in Italy and will be delivered in June 2000 for the acceptance test at Steward Observatory (Tucson, AZ). The latest results obtained on a reduced-size (36 actuators) prototype called P36 are reported, confirming a settling time less than 1 ms measured in previous tests. .....


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[4007-06] Optical fabrication of the MMT adaptive secondary mirror

H. M. Martin, J. H. Burge, Steward Observatory/Univ. of Arizona
C. Del Vecchio, Astrophysical Observatory of Arcetri (Italy);
L. R. Dettmann, S. M. Miller, B. K. Smith, F. P. Wildi, Steward Observatory/Univ. of Arizona

We describe the optical fabrication of the adaptive secondary mirror for the MMT. The 640 mm f/15 secondary consists of a flexible glass shell, 1.8 mm thick, whose shape is controlled by 336 electromagnetic actuators. It is designed to give diffraction-limited images at a wavelength of 1 micron. For generating and polishing, the shell was supported by attaching it to a rigid glass blocking body with a thin layer of pitch. It could then be figured and measured using techniques developed for rigid secondaries. The highly aspheric surface was polished with a 30 cm stressed lap and small passive tools, and measured using a swing-arm profilometer and a holographic test plate. The goal for fabrication was to produce diffraction-limited images in the visible, after simulated adaptive correction using only a small fraction of the typical actuator forces. This translates into a surface accuracy of less than 19 nm rms with correction forces of less than 0.05 N rms. We achieved a surface accuracy of 8 nm rms after simulated correction The adaptive optics system for the 6.5 m MMT is based on an adaptive secondary mirror designed to give diffraction-limited images in the near-infrared, between 1 and 5 microns.


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[4007-08] LBT adaptive secondary preliminary design

D. Gallieni, ADS International s.r.l. (Italy)
C. Del Vecchio, Astrophysical Observatory of Arcetri (Italy)
E. Anaclerio, ADS International s.r.l. (Italy)
P. G. Lazzarini, ADS International s.r.l. (Italy)

We report on the design of the two Gregorian adaptive secondary mirrors of the Large Binocular Telescope. Each adaptive secondary is a 911 m wide and 1.5 mm thick Zerodur shell controlled by a pattern of 918 electromagnetic actuators. The shape of the mirror is referred to a stable ULE backplate by means of capacitive sensors co-located to the actuators pattern. The preliminary design of the system is addressed with particular attention to the reference plate optimization.


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[4007-09] Numerical simulations of the LBT adaptive secondary mirror

C. Del Vecchio, Astrophysical Observatory of Arcetri (Italy)
D. Gallieni, ADS International s.r.l. (Italy)

In this paper we describe the design of the deformable mirror of the Large Binocular Telescope adaptive secondary unit. Starting from the optical design, a numerical model of the ultra-thin, aspherical glass shell, accommodating the 918 magnets on the selected actuator geometry, has been run. Using this model, we can evaluate the response of this crucial component of the telescope optics with great accuracy. The DM is analyzed from the mechanical standpoint -- gravity deformations, wavefront residue, corrections of magnetic interactions, dynamics -- in order to compute the optical performances in the most demanding operational circumstances.


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[4007-27] Atmospheric tomography with Rayleigh laser beacons for correction of wide fields and 30 m class telescopes

J. R. P. Angel and M. Lloyd-Hart, Steward Observatory, The University of Arizona

Single sodium beacons will likely be the most convenient for adaptive systems to correct 6-10 m class telescopes over a small field of view (the isoplanatic angle), provided reliable, powerful 589 nm lasers become available and affordable. However, when adaptive optics are applied to extended fields of view and correction of telescopes as large as 32 m diameter, it seems likely that laser beacons produced by Rayleigh scattering will be preferred. For these more demanding applications which require atmospheric tomography, Rayleigh beacons come into their own for two reasons. First, the cone effect, which causes the high turbulence to be sampled at a different scale, is no longer problematic when multiple lasers are used and height dependence is solved for explicitly. Second, the tomographic solution can make use of the beacon created by a laser pulse during all of its journey through the upper atmosphere, not just scattering from a thin layer selected by range gating. In this way a laser that costs an order of magnitude less to buy and maintain than a sodium laser of the same power can yield a brighter beacon and more information about the atmospheric turbulence. This is important because both the number and brightness of beacons or stars must increase with the number of layers included in the tomographic solution. For the same reason, tomography with natural stars is unlikely to be valuable for very large telescopes because in general the number and required brightness of each star increase with corrected field angle, while current narrow-field adaptive optics systems relying on natural stars are already very limited in sky coverage. Our method for tomography to take advantage of Rayleigh scattering over a wide range of heights uses short pulses from near diffraction-limited, ultraviolet lasers, projected from a small aperture above the telescope s secondary mirror. Each pulse subtends less than 1 arcsec at any instant as it travels up through many kilometers. An imaging detector at the main telescope focus conjugate to mid-height is used to record fast movies of the rising pulses as they come into and out of focus. Phase diversity analysis of the movies taken together then yields the three-dimensional turbulence of the atmosphere.


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[4007-30] New Approach to Rayleigh Guide Beacons

M. Lloyd-Hart, S. M. Jeffries, E. K. Hege and J. R. P. Angel, Steward Observatory/Univ. of Arizona

We present analysis and numerical simulations of a new method to sense atmospheric wavefront distortion in real time with Rayleigh beacons. Multiple range-gated images of a single pulse from the laser are used to determine each phase map, provid-ing an advantage over other methods in that photon noise is substantially reduced for a given brightness of the beacon. A laser at about 350 nm projects collimated pulses of light adjacent to the telescope. Rayleigh-scattered light from each pulse is recorded through the full telescope aperture in a sequence of video frames, each a few ms long. Images are captured as the pulse approaches and passes through the height at which the camera is focused. Phase diversity is thus naturally introduced between the frames. An iterative algorithm is used to extract the pupil-plane phases from the recorded intensity distributions. We anticipate that such beacons are likely to be valuable in future advanced systems for adaptive optics on very large tele-scopes with multiple laser beacons and deformable mirrors that aim to provide a large corrected field of view by tomography of the atmospheric turbulence.


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[4007-51] Wavefront sensing and guiding units for the Large Binocular Telescope

Jesper Storm, Astrophysikalishes Institut Potsdam (AIP), Germany
Walter Seifert, Landessternwarte Heidelberg, Germany
Svend Marian Bauer, AIP, Germany
Frank Dionies, AIP, Germany
Ulfert Hanschur, AIP, Germany
John Hill, Steward Observatory, Tucson, USA
Guenther Moestl, AIP, Germany
Piero Salinari, Arcetri Observatory, Firenze, Italy
Waldemar Varava, AIP, Germany
Hans Zinnecker, AIP, Germany

The Large Binocular Telescope (LBT) will be equipped with fully adaptive secondary mirrors from first light which is currently planned for mid-2002. To allow the science instruments to benefit from this feature, we ar ecurrently designing a set of wavefront sensing systems for the base-line telescope. One of the design goals is to take full advantage of the fact that the adaptive correction is performed with the secondary mirror which means that we do not have to introduce an additional warm surface in the IR beam. Consequently we will follow the upgraded-MMT concept of using the light reflected off a tilted instrument entrance window for the tip-tilt guiding as well as for the wavefront sensing. Another design goal is to have an upgrade path ready for the first few years of operation which will allow us to migrate from the use of natural stars to the use of either sodium laser stars or Rayleigh beacons as the light source for the adaptive optics sensing. The three techniques operate in quite different ways which introduces significantly different constraints on the design. In particular the Rayleigh beacons are complicated as a minimum of four simultaneous beams has to be observed and it is necessary to be able to focus down to altitudes of the order 20km. We will present the current status of our design including the proposed upgrade path. The expected performance will also be outlined.


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[4007-56] Adaptive optics simulation tests for imaging with the Large Binocular Telescope

M. Carbillet, S. Correia, B. Femenia, A. Riccardi, Osservatorio Astrofisico di Arcetri

In this contribution we present a first application of the ongoing numerical simulations that are carried out in order to study the adaptive optics (AO) correction and the subsequent imaging post-processing when observing with the Large Binocular Telescope (LBT) interferometer. The simulation tool used as a starting point for this study is the software package CAOS 2.0 (Code for Adaptive Optics Systems, version 2.0), for its AO-simulation capabilities and its modular structure. It is used here in order to generate the turbulence-corrupted and subsequently adaptive-optics- corrected interferometric point-spread functions corresponding to the simultaneous observation of both a scientific object and a reference star, for three parallactic angles corresponding to three observation runs during the night. The obtained data are therefore used as the inputs of a multiple deconvolution method planned for imaging with the LBT interferometer. As an example, we have simulated the observation, in the R-band, of a Betelgeuse-like stellar object of 15th magnitude, 30 mas diameter, and with a 3 mas bright spot, under two different conditions of turbulence and AO-correction (leading to Strehl ratios of ~0.15 and ~0.45, respectively). Final results are found to be very encouraging.


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[4007-121] Adaptive optics for the 6.5m MMT

M. Lloyd-Hart, F. P. Wildi, G. Z. Angeli, W. B. Davison, B. C. Fitz-Patrick, R. L. Johnson, M. A. Kenworthy, P. C. McGuire, B. Martin, S. M. Miller, and J. R. P. Angel, Steward Observatory/Univ. of Arizona

The adaptive optics system for the 6.5m MMT conversion telescope will be the first to compensate the aberrated wavefront at the telescope's secondary mirror. This approach has unique advantages in terms of optical simplicity, high throughput and low emissivity. We report here the present state of construction, and the results of static and dynamic performance tests of the Cassegrain optical package.


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Conference 4008: Optical and IR Telescope Instrumentation and Detectors

[4008-49] A Double Prime Focus Camera for the F/1.14 Large Binocular Telescope.
R. Ragazzoni[1], E. Giallongo[2], F. Pasian[3], F. Pedichini[2], M. Turatto[1], and D. Gallieni[4]

1: Astronomical Observatory of Padova (Italy)
2: Astronomical Observatory of Roma (Italy)
3: Astronomical Observatory of Trieste (Italy)
4: ADS International srl (Italy)

The Large Binocular Telescope is currently in the pre-erection phase. The prime focus instrument will be used at the first light and its final design have been carried out during last months. Given the peculiarity of the telescope optics (a double 8.4m mirrors on the same mounting) we designed two prime focus camera with a five-lens refractive correctors, optimized in the blue-side (namely U and B Johnson bands) and red-side (V, R and I Johnson bands) of the visible spectrum. This independent optimization is effective both in the optical design, whose achromaticity requirements are relaxed, and both from the coating side. Detectors also reflects this choice, being optimized separately We present the most relevant features of the instrument and the optical design as well as the structural and mechanical layout. Each of the two Prime Focus camera gather light from a very fast, F/1.14 parabolic primary mirror. The field is corrected over roughly half a degree in size, allowing optical performances in terms of 80% of Encircled Enedrgy in better than ~0.3arcsec. Focal length is slightly augmented in order to provide a better pixel sampling using 13.5um EEV chips. The CCD array is made up with 4 EEV 42-90 chips, on both channels, to obtain an equivalent 6000 x 6000 pixels optimzing the AR coating to the U-B-V and V-R-I bands respectively. The array will be readed out in 10 seconds using a 1 Megapixel/second controller with four video channels. The cryostat will use a state of the art dewar to reach an holding time of several days using a limited amount of liquid nitrogen to avoid misbalancing of the telescope during evaporation. The whole mechanical design has been modelled using Finite Elements analysis in order to check for mechanical flexures of the mount tube and of the optical components by themseleves. A brief overview of the informatic facilities to be provided with the instrument and of a few science case studies that can be attacked from this instrument are also givne. Current the instruemtn has been partially funded for its realization whose first-light is expected shortly after the one of the LBT.

pp. 439-446


[4008-05] Multiobject double spectrograph for the Large Binocular Telescope

P. S. Osmer, B. Atwood, P. L. Byard, D. L. DePoy, T. P. O'Brien, R. W. Pogge, D. Weinberg, Department of Astronomy, The Ohio State University.

We are designing and will build a Multi-Object Double Spectrograph (MODS) for the Large Binocular Telescope (LBT). The main themes of our planned research for the LBT with MODS will be the formation of and evolution of galaxies and their nuclei, and the evolution of large-scale structures in the universe (although MODS will be used for many areas of modern astrophysics). The combination of the light gathering power of the LBT with the multi-object capability of MODS will allow study of the chemical, dynamical, and assembly history of galaxies, the history of cosmic star formation, and the evolution of three-dimensional structure in the distributions of high-redshift galaxies, Lyman-limit systems, and Ly-a forest absorbers, all in unprecedented detail. The high efficiency of MODS over the full optical band will enable observations of key spectral features in galaxies and quasars from z=0 to z=7.

The MODS instrument will have a range of intermediate spectral resolutions (1000-10000 for a 0.6 arcsec wide slit) and will deliver high throughput from 320 to 1000 nm through the use of two separate optical channels optimized individually for blue and red wavelengths. It will have multi-object capability over a 4’ field as well as a cross-dispersed mode. The design will allow for future upgrades of additional cameras, integral field capability (to take advantage of projected adaptive optics for LBT), and other gratings. MODS will use an open architecture, modular design approach, and a minimum number of optical elements. This will result in a flexible and powerful instrument while keeping the project costs down.

The construction of MODS will be the main instrumentation project for the OSU Astronomy Department for the next several years.

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pp. 40-49


[4008-16] Design study for an Adaptive Optics Visual Echelle Spectrograph (AVES) for the VLT

R. Pallavicini, P. Caldara, Osservatorio Astronomico di Palermo, Italy
L. Pasquini, B. Delabre, N. Hubin, European Southern Observatory, Garching bei Muenchen, Germany
P. Molaro, P. Bonifacio, P. Santin, P. Dimarcantonio, M. Comari, Osservatorio Astronomico di Trieste, Italy
L. Mantegazza, R. Mazzoleni, E. Molinari, F. Zerbi, Osservatorio Astronomico di Brera, Milano
G. Bonanno, S. Catalano, M. Rodono, Osservatorio Astrofisico di Catania. Italy

A design study is currently underway by a consortium of Italian Institutes and collaborating scientists at ESO for the development of an Adaptive Optics Visual Echelle Spectrograph (AVES) for the VLT. A preliminary concept for the instrument was presented at the SPIE conference in Kona in 1998. The instrument is intended for medium-resolution (R ~ 20,000) spectroscopy of faint sky-limited or detector limited observations of galactic and extragalactic objects, down to a magnitude limit of R=22. In its current design, it is conceived for a possible use as parallel instrument of the Nasmyth Adaptics Optics System (NAOS) at the ESO VLT, but it could also be used, with some modifications, at other large telescopes with adaptive optics capabilities (e.g. the LBT). The opto-mechanical design will be presented, together with the specifications for Instrument Control Software, electronics and detector system. The possibility of adding an imaging mode will also be discussed. The advantages of adaptive optics for medium and high-resolution spectroscopy will be highlightened.

pp. 167-174


[4008-83] LUCIFER - a NIR spectrograph and imager for the LBT

Holger Mandel, Immo Appenzeller, Ralf Mohr, Walter Seifert, Wenli Xu, Landessternwarte Konigstuhl 12 D-69117 Heidelberg, Germany
Tom Herbst and Rainer Lenzen, Max Planck Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany
Niranjan Thatte and Frank Eisenhauer, Max Planck Institut fur Extraterrestrische Physik, P.O. Box 1603, D-85740 Garching, Germany
Roland Lemke, Dominik Bomans, Thomas Luks, Astronomisches Institut der Ruhr-Universitat Bochum, Universitatsstr. 150, D-44780 Bochum, Germany
Peter Weiser, Fachhochschule fur Technik und Gestaltung, Windeckstr. 110, D-68163 Mannheim

LUCIFER (LBT NIR-Spectroscopic Utility with Camera and Integral-Field Unit for Extragalactic Research) is a full cryogenic NIR spectrograph and imager to be build by a consortium of five institutes (Landessternwarte Heidelberg, Max Planck Institut fur Astronomie in Heidelberg, Max Planck Institut fur Extraterrestrische Physik in Garching, Astronomisches Institut der Ruhr-Universitat Bochum and of the Fachhochschule fur Technik und Gestaltung in Mannheim). The instrument has been chosen as one of three first-light instruments for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona which becomes available to the community in autumn 2002. A second instrument follows 18 month later.

Both LUCIFER-instruments will be mounted at the bent Gregorian focii of the two individual LBT-mirrors and includes six observing-modes:
- Seeing limited imaging over a 4 arcmin FOV
- Seeing limited longslit spectroscopy
- Seeing limited multi-object spectroscopy (MOS)
- Diffraction limited imaging over a 0.7 arcmin FOV
- Diffraction limited longslit spectroscopy
- Integral field spectroscopy (IFU)

According to the present schedule the Preliminary Design Review (PDR) for the project will be hold in February 2000, the Critical Design Review (CDR) follows in June/July 2000. At this meeting first results of our optical and cryo-mechanical design studies are presented.

pp. 767-777


[4008-111] MODS: Optical Design for a Multi-Object Dual Spectrograph

P. L. Byard, T. P. O'Brien, Department of Astronomy, The Ohio State University

The paper describes the optical design for the Multi Object Dual Spectrograph (MODS) for the Large Binocular Telescope (LBT). MODS is designed to cover the entire spectrum accessible to silicon CCDs from a ground-based telescopes with the highest possible throughput. Multi-object capability is available using 0.6 arc-second slit masks covering a high quality field of 4 arc-minutes in diameter with an extended field of up to 6 arc-minutes in diameter with reduced image quality. Under the very best seeing conditions and with the LBT adaptive optics in operation, slit widths of 0.3 arc seconds can be used to enhance the resolving power and/or reduce the background.

The optical path is divided into blue and red channels by a dichroic beam splitter following the slit or slit masks. The blue channel covers a wavelength range from the atmospheric cut-off at ~300 nm to ~ 650 nm while the red channel covers the range from ~650 nm to the limit of useful sensitivity of silicon CCDs (~1000 nm). This approach allows the optimization of transmissive and reflective coatings to provide the very highest throughput for each channel.

The design is conventional in the use of reflective parabolic collimators. However, the cameras are designed as decentered Schmidt/Maksutovs with large aspheric coefficients for the inner surface of the corrector and mirror. This approach enables the field flattener and detector to be positioned outside the beam entering the camera where it will not add to the loss of light within the system. Figures are presented showing image quality for imaging and spectrographic modes.

pp. 934-941


[4008-126] LUCIFER-MOS: A cryogenic multi-object infrared spectrograph for the LBT

R. Hofmann, N. Thatte, M. Tecza, F. Eisenhauer, M. Lehnert, Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany

We present the MOS unit for LUCIFER, the cryogenic near-infrared spectrograph for the Large Binocular Telescope (LBT). The MOS unit consists of 15 deployable integral field units (d-IFUs), each sampling 30 object points covering a small field of view of 2 arc seconds. The individual IFUs consist of a bundle of monolithic lenslet-fiber units made from silica-silica fibers, so as to achieve high fill factors in the focal plane. A cryogenic robotic fiber positioner will reposition the d-IFUs within a field of 4 x 4 arc minutes. The output of the fibers will be fed to the LUCIFER spectrograph, which will provide high resolution spectroscopy (R ~ 5000) covering one of the J, H or K atmospheric windows. The entire MOS unit operates at 77 K, ensuring low thermal background and high sensitivity. The large apertures of the LBT, and the use of OH avoidance techniques will enable infrared multi-object spectroscopy of faint high redshift galaxies with the LUCIFER MOS unit.

pp. 1094-1102


[4008-58] PMAS Fiber Spectrograph: Design, Manufacture and Performance

M. M. Roth, Leibniz Institute for Astrophysics Potsdam
U. Laux, Weimar, Germany
W. Heilemann, Carl Zeiss Jena, Germany

PMAS, the Potsdam Multi-Aperture Spectrophotometer is currently being developed as a travelling instrument of AIP. It is prototyped for first light at the Calar Alto 3.5m telescope with an option to go to other telescopes with little modification. PMAS is a high efficiency integral field spectrograph with low/medium spectral resolution, covering the whole optical wavelength range from 350 to 900nm without refocus. With the requirements of spectral and photometric stability it is therefore an ideal instrument for spectrophotometry with full 2-dimensional spatial resolution. The layout consists of a lens array, coupled to a fiber bundle, which is fed to the fiber spectrograph. The spectrograph is a fully dioptric 150/450mm collimator and 180/270mm camera system for reflective gratings. It is corrected over the whole nominal wavelength range with average/maximum 80% design spot concentrations of 12/20um for the camera, and 14/24um for the whole system, respectively. The lenses which are made from Schott glasses and CaF2 blanks have been fabricated and integrated into complete systems by Carl Zeiss Jena, Germany. We will describe the optical design and report on the measured performance.

pp. 485-496


[4008-28] PMAS Design and Integration

M. M. Roth, S-M. Bauer, F. Dionies, T. Fechner, T. Hahn, A. Kelz, J. Paschke, E. Popow, J. Schmoll, D. Wolter, Leibniz Institute for Astrophysics Potsdam
W. Altmann, Tiefenbach
U. Laux, Weimar, Germany

PMAS, the Potsdam Multi-Aperture Spectrophotometer has been designed and is currently being integrated as a traveling instrument of the Leibniz Institute for Astrophysics Potsdam. It is a UV-Visual integral field spectrograph, with optimized efficiency and stability for use as a 3D spectrophotometer. PMAS is prototyped for first light at the Calar Alto 3.5m telescope with an option to go to other telescopes (e.g. LBT). We present the final design layout, details of the mechanics including results from FE studies, the optics, detector systems, and instrument control. We will report on the current status of the integration.

pp. 277-288


Conference 4015: Radio Telescopes

[4015-30] Submillimeter-wave receiver system for the Large Binocular Telescope

C. Y. Drouet d'Aubigny, C. K. Walker, C. E. Groppi, J. M. Hill and J. H. Bieging, Steward Observatory/Univ. of Arizona
S. M. Pompea, Pompea & Associates

The Large Binocular Telescope (LBT) now under construction by the LBT Corporation partners on Mt. Graham, Arizona will offer unique opportunities for observing at submillimeter wavelengths. The LBT will be composed of two 8.4m optical quality mirrors mounted on a common support structure. When used as an interferometer, the telescope will be able to achieve the diffraction limited resolution of a 22.8m aperture. At 350 microns, the LBT primaries will be essentially perfect (20 nm rms) and have a total light gathering power equivalent to a state-of-the-art (main beam efficiency ~0.35), ~19 meter diameter submillimeter telescope. In our presentation we will describe a coherent beam combiner and focal plane receiver system which will permit phase-switched, interferometric observations to be performed with LBT at 350 microns. First light observations with a single LBT mirror are expected in 2002, with interferometric observations beginning after the installation of the second mirror about 1.5 years later.


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Astronomical Telescopes and Instrumentation 2000
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