LBT at the Astronomical Telescopes and Instrumentation 2002 Meeting
22-28 August 2002, Waikoloa, Hawaii USA
Sponsored by the SPIE, The International Society for Optical Engineering
Abstracts and LBT-related papers:
Conference 4837: Large Ground-Based Telescopes
[4837-15] 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. The first of two 8.4-meter borosilicate honeycomb primary mirrors for LBT is being polished at the Steward Observatory Mirror Lab this year. The second of the two 8.4-meter mirror blanks waits its turn in the polishing queue. 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. These adaptive secondary mirrors with 672 voice-coil actuators are now in the early stages of fabrication. 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 for phased array imaging. 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. The telescope structure accommodates installation of a vacuum bell jar for aluminizing the primary mirrors in-situ on the telescope. The telescope structure was fabricated and pre-assembled in Italy by Ansaldo-Camozzi in Milan. The structure was disassembled, packed and shipped to Arizona. The enclosure was built on Mt. Graham and is ready for telescope installation.
gzip'd Postscript file (73634 kB)
PDF file (4565 kB)
[4837-24] Completion of the Large Binocular Telescope Enclosure
Jose Teran U., James H. Slagle, John M. Hill and Daniel H. Neff,
M3 Engineering & Technology Corp and the University of Arizona
The Large Binocular Telescope (LBT) under construction on Mount Graham, Arizona is a unique instrument, which supports two 8.4-meter primary mirrors on the same mount. The telescope mirrors will provide a collecting area equivalent to an 11.8 circular aperture plus a diffraction baseline of 22.8 meters. This unique instrument presented new enclosure challenges and configurations in order to accommodate the Owner's design, telescope operating criteria and budget.
The LBT enclosure completed in the summer of 2002 provides useful information on the planning, designing and construction of a telescope enclosure. The use of a team approach by the contractors, engineers, and the project office has been successful in maintaining quality construction at a reasonable price. This paper discusses the various systems implemented on the LBT enclosure and the lessons learned during the course of the design and construction.
MS Word file (10737 kB)
[4837-69] Fabrication of Mirrors for the Magellan telescopes and the Large Binocular Telescope
H. M. Martin, et al., The University of Arizona
We describe the fabrication and testing of the 6.5m f/1.25 primary mirrors for the Magellan telescopes and the 8.4m f/1.14 primary mirrors for the Large Binocular Telescope (LBT). These mirrors, along with the 6.5m MMT primary, are the fastest and most aspheric large mirrors ever made........
gzip'd Postscript file (7213 kB)
Conference 4838: Interferometry for Optical Astronomy II
[4838-13] The Large Binocular Telescope Interferometer
P. M. Hinz, J. R. P. Angel, D. W. McCarthy, W. F. Hoffmann, C. Y. Peng, U of A
The Large Binocular Telescope (LBT), with dual 8.4 m optics on a common mount,is unique among the large-aperture interferometers. Deformable secondaries on the telescope capable of adaptive atmospheric correction allow beam combination after only three warm reflections. The design allows the implementation of two powerful uses of interferometry: suppression of starlight (or nulling interferometry) and wide-field imaging (or Fizeau interferometry). Nulling will allow detection of extrasolar planetary systems (from either zodiacal emission or giant planets)down to solar system-equivalent levels for nearby stars. This will dramatically increase our knowledge of the prevalence and make-up of extrasolar planetary systems. Fizeau interferometry will allow imaging of even complex structure at the resolution of a 22.8 m telescope. To implement these two powerful techniques the University of Arizona and NASA are collaborating to build the Large Binocular Telescope Interferometer (LBTI) a cryogenic instrument capable of sensitive interferometric observations in the infrared.
[4838-109] Performance of the restoration of interferometric images from the Large Binocular Telescope -- the effects of
angular coverage and partial adaptive optics correction
M. Carbillet, Osservatorio Astrofisico di Arcetri
with S. Correia, P. Boccacci and M. Bertero
This presentation reports the status of our study concerning the imaging properties of the Large Binocular Telescope (LBT) interferometer, and namely the effects of limited angular coverage and partial adaptive optics (AO) correction. The limitation in angular coverage, together with the correlated problem of angular smearing due to time-averaging of the interferometric images, is investigated for relevant cases depending on the declination of the observed object. Results are encouraging even in case of incomplete coverage. Partial AO-correction can result in a wide range of image quality, but can also create significant differences within a same field-of-view, especially between a suitable reference star to be used for post-observation multiple deconvolution and the observed object. Our study deals with both the problem of space-variance of the AO-corrected point-spread function, and that of global quality oftheAO-correction. Uniformity, rather than global quality, is found to be the key-problem. After considering the single-conjugate AO case, we reach to some conclusions for the more interesting, and actually wide-field, case implying multi-conjugate AO. The whole study is performed on different types of object, from binary stars to diffuse objects, and a combined one with a high-dynamic range.
[4838-110] LINC-NIRVANA a Fizeau beam combiner for the Large Binocular Telescope
T. M. Herbst, MPIA Heidelberg, R. Ragazzoni, Osservatorio Astrofisico di Arcetri and many others
Fizeau interferometry at the Large Binocular Telescope (LBT) offers significant advantages over other facilities in terms of spatial resolution, field of view, and sensitivity. We provide an update of the LINC-NIRVANA project, which aims to bring a near-infrared and visible wavelength Fizeau beam combiner to the LBT by late 2005. As with any complex instrument, a number of detailed requirements drive the final design adopted.
Conference 4839: Adaptive Optical System Technologies II
[4839-20] First Light Adaptive Optics System for Large Binocular Telescope
Simone Esposito, Osservatorio Astrofisico di Arcetri and a cast of thousands
The paper describes the design of the single conjugate Adaptive Optics system to be installed on the LBT telescope. This system will be located in the Acquisition, Guiding and Wavefront sensor unit (AGW) mounted at the front bent Gregorian focus of LBT. Two innovative key features of this system are the Adaptive Secondary Mirror and the Pyramid Wavefront Sensor. The secondary provides 672 actuators wavefront correction available at the various foci of LBT. Due to the adaptive secondary mirror there is no need to optically conjugate the pupil on the deformable mirror. This allows having a very short sensor optical path made up using small dimension refractive optics. The overall AO system has a transmission of 70 % and fits in a rectangle of about 400x320mm. The pyramid sensor allows having different pupil sampling using on-chip binning of the detector. Main pupil samplings for the LBT system are 30x30, 15x15 and 10x10. Reference star acquisition is obtained moving the wavefront sensor unit in a field of view of 3x2 arcmin. Computer simulations of the overall system performance show the good correction achievable in J, H, and K. In particular, in our configuration, the limiting magnitude of pyramid sensor results more than one magnitude fainter with respect to Shack- Hartmann sensor. This feature directly translates in an increased sky coverage that is, in K band, about doubled with respect to the same AO system using a Shack-Hartmann sensor.
PDF file (1268 kB)
[4839-85] Adaptive Secondary Mirrors for the Large Binocular Telescope
A. Riccardi, Osservatorio Astrofisico di Arcetri et al.
The two adaptive secondary (AS) mirrors for LBT (LBT672) represent the new generation of the AS technology. Their design is based on the experience earned during the extensive tests of the previous generation unit (the MMT AS mirror). Both the mechanics and the electronics have been revised, improving the stability, reliability, maintenance and computational power of the system. The deformable mirror of each unit consists of a 1.6mm-thick Zerodur shell having a diameter of 911mm. The front surface is concave to match the Gregorian design of the telescope. Its figure is controlled by 672 electro-magnetic force actuators that are supported and cooled by an aluminum plate. The actuator forces are controlled using a combination of feed-forward and de-centralized closed loop compensation, thanks to the feedback signals from the 672 co-located capacitive position sensors. The surface reference for the capacitive sensors is a 50mm-thick Zerodur shell faced to the back surface of the thin mirror and rigidly connected to the support plate of the actuators. Digital real-time control and unit monitoring is obtained using new custom-made on-board electronics based on new generation 32bit oating-point DSPs. The total computational power (121 G op/s) of the LBT672 units allows using the control electronics as wave-front computer without any reduction of the actuator control capability. We report the details of the new features introduced in the LBT672 design and the preliminary laboratory results obtained on a prototype used to test them. Finally the facility in Arcetri to test the final LBT672 units is presented
Powerpoint presentation (5385 kB)
[4839-90] LBT adaptive secondary units final design and construction
D. Gallieni, ADS International
E.Anaclerio, P.G.Lazzarini, A.Ripamonti, R.Spairani, C.DelVecchio, P.Salinari, A.Riccardi, P.Stefanini, R.Biasi
The Large Binocular Telescope will perform its first level AO correction at visual wavelengths by the two Gregorian secondary mirrors. Each unit is made by a 911 mm diameter and 1.6 mm thick Zerodur shell which shape is controlled by 672 electromagnetic actuators at 1 kHz rate. The shape of each mirror is referred to a Zerodur 50 mm thick backplate through a set of capacitive sensors co-located with the actuators. Each adaptive secondary unit embeds its real time computer for actuator control and communication. Each unit is aligned into the secondary hub by a 6 d.o.f. hexapod system. The construction of the AO units started this year, while the hexapods have been completed in 2001. We present in this paper the final design of the adaptive secondary systems with particular emphasis on the modifications that we made based on the MMT adaptive secondary experience. We will also report the first results of the subsystems development tests.
PDF file (1948 kB)
Powerpoint poster for 4839-90 and 4839-91 (3752 kB)
[4839-91] LBT adaptive secondary electronics
Roberto Biasi, Microgate S.r.l.
Mario Andrighettoni, Daniele Veronese, Valdemaro Biliotti, Luca Fini, Armando Riccardi, P.Mantegazza, D.Gallieni
The adaptive secondary mirror is a fundamental part in the LBT adaptive optics architecture. The thin, continuous mirror is controlled by 672 electromagnetic actuators (voice coil motors) with local position feedback (capacitive sensor) and allows to perform from tip-tilt to high order wavefront correction, but also chopping. The adaptive secondary is controlled by a DSP-based dedicated electronics. The control electronics does not only implement the mirror position control tasks, but does also realize the Real Time Reconstructor (RTR). The control system, while maintaining a similar architecture to the MMT adaptive secondary one, shows a substantial enhancement in terms of computational power, rising in the range of hundreds of Gigaflops. This allows to minimize the computational time required to apply the wavefront correction pattern from the wavefront sensor acquisition, even in case of high order reconstructor dynamics. The electronics is housed in compact cooled crates placed in the adaptive secondary hub. Apart from the power supply lines, it is connected to the other components of the adaptive control system just through a very high speed fiber optic link, capable of 2.9 Gigabit/s of actual data throughput. The control system has been designed according to modular concept, so that the number of channels can be easily increased or reduced for adapting the electronics to different correctors. A substantial effort has been dedicated to the flexibility and on-field configurability of system. In this frame, the same electronics (or part of it) can be easily adapted to become the building block for the data processing unit required for Multi-Conjugated Adaptive Optics.
PDF file (184 kB)
Powerpoint poster for 4839-90 and 4839-91 (3752 kB)
[4839-101] Large Binocular Telescope Facility SCIDAR: First Results
D. L. McKenna, Steward Observatory
R. Avila, UNAM
J. M. Hill, The University of Arizona
S. Hippler, MPIA
Piero Salinari, Osservatorio Astrofisico di Arcetri
P. C. Stanton, Alacron Inc.
R. Weiss, MPIA
We present the design and recent results from the Large Binocular Telescope (LBT) facility SCIDAR. To our knowledge, this work is the first SCIDAR designed as a user instrument for routine seeing measurements in support of telescope operations. Using a commercial off-the-shelf approach, we have minimized the resources required for system construction.
PDF file (1222 kB)
[4839-149] Performance of the First-Light Adaptive Optics System of LBT by Means of CAOS Simulations
Marcel Carbillet, Osservatorio Astrofisico di Arcetri and others
This presentation reports the numerical simulations we have done in order to evaluate the performance of the rst-light AO system of LBT. The simulation tool used for this purpose is the Software Package CAOS, applicable for a wide range of AO systems and for which a brief recall of the main features is made. The whole process of atmospheric propagation of light, wavefront sensing (using a complete model of the pyramid wavefront sensor), wavefront reconstruction (using the LBT672 adaptive secondary mirror modes), and closing of the loop, is simulated. The results are given in terms of obtained Strehl ratios in J-, H-, and K-band. Estimation of the resulting sky-coverage in K-band for di erent regions of the sky are also expressed. A comparison with the performance that would be obtained by using a Shack-Hartmann sensor is presented, con rming the gain achievable with the pyramid sensor. Keywords: Large Binocular Telescope, rst-light adaptive optics system, pyramid wavefront sensor, numerical simulations 1.
PDF file (833 kB)
Conference 4841: Instrument Design and Performance for Optical/Infrared Ground-Based Telescopes
[4841-05] Overview of Instrumentation for the Large Binocular Telescope
R. M. Wagner, LBTO, The University of Arizona
An overview of the 3 facility instruments and 2 strategic interferometric instruments under construction for the Large Binocular Telescope is presented. Planned optical instrumentation includes the Large Binocular Camera (LBC), a pair of wide-field (25 x 25 arcmin) UB/VRI optimized mosaic CCD imagers at the prime focus, and the MultiObject Double Spectrograph (MODS), a pair of dual-beam blue-red optimized longslit spectro- graphs mounted at the straight-through F/15 Gregorian focus incorporating multiple slit masks for multi-object spectroscopy over a 5 arcmin field and spectral resolutions of 2000-8000. Infrared instrumentation includes the LBT Near-IR Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER), a modular near-infrared (0.9-2.5 micron) imager and spectrograph pair mounted at a bent interior focal station and designed for seeing limited (FOV: 4 x 4 arcmin) and diffraction limited (FOV: 0.5 x 0.5 arcmin) imaging and longslit spectroscopy, seeing limited multiobject spectroscopy utilizing cooled slit masks, and optional diffraction limited integral field spectroscopy. Strategic instruments under development include an interferometric cryogenic beam combiner with NIR and thermal IR instruments for Fizeau imaging and nulling interferometry, and an optical bench beam combiner with visible and NIR imagers utilizing in the future multi-conjugate adaptive optics for angular resolutions as high as 5 mas at a wavelength of 0.5 micron. The availability of all these instruments mounted simultaneously on the LBT permits flexible scheduling and improved operational support.
gzip'd Postscript file (3162 kB)
PDF file (1449 kB)
[4841-44] Adjustable Truss for Support, Optical Alignment, and
Athermalization of a Schmidt Camera
T.P. O’Brien, B. Atwood, Ohio State University
The MODS optical spectrograph uses a de-centered Maksutov-Schmidt camera with a clear aperture of ~300mm. This large camera has two widely spaced elements, the corrector and the camera mirror, and a field flattener near the focal plane. This paper describes the truss system that supports the optical elements very rigidly, uses adjustable length links to provide a deterministic method for alignment of the optical elements, and uses material combinations which result in a camera with nearly zero focus shift due to changes in temperature. A novel joint design for terminating the truss links is described that has excellent stiffness and enhances ease of assembly and alignment.
PDF File (362 kB)
[4841-60]Blue and red channels of LBC:
a status report on the optics and the mechanics
Emiliano Diolaiti, Università di Padova
Roberto Ragazzonib, Osservatorio Astrofisico di Arcetri, Max Planck Institut für Astronomie
Fernando Pedichinid, Osservatorio Astronomico di Roma
Roberto Speziali, Osservatorio Astronomico di Roma
Jacopo Farinato, Osservatorio Astrofisico di Arcetri
Daniele Gallieni, ADS International
Enzo Anaclerio, ADS International
Paolo Lazzarini, ADS International
Raffaele Tomelleri, Studio Tecnico Tomelleri
Pierfrancesco Rossettinif, Studio Tecnico Tomelleri
Emanuele Giallongo, Osservatorio Astronomico di Roma
The Large Binocular Camera (LBC) is a double prime focus station to be mounted on the Large Binocular Telescope (LBT). The two channels, called Blue and Red, are optimized for the UB and VRIZ bands respectively and are characterized by two optical correctors with very fast focal ratio (F/1.45) and challenging optical and mechanical specifications. We present here a review of the optical and mechanical design of both the optical correctors and report on the current status of the manufacturing and integration.
[4841-87] LBC: the prime focus optical imagers at the LBT telescope
F. Pedichini, INAF Oss. Astr. Roma
E. Giallongo, INAF Oss. Astr. Roma
R. Ragazzoni, INAF Oss. Astr. Arcetri
A. Di Paola, INAF Oss. Astr. Roma
A. Fontana, INAF Oss. Astr. Roma
R. Speziali, INAF Oss. Astr. Roma
J. Farinato, INAF Oss. Astr. Arcetri
A. Baruffolo, INAF Oss. Astr. Padova
C. Magagna, INAF Oss. Astr. Padova
E. Diolaiti, Astronomical dep. Padua University
F. Pasian, INAF Oss. Astr. Trieste
R. Smareglia, INAF Oss. Astr. Trieste
E. Anaclerio, ADS International
D. Gallieni, ADS International
P. G. Lazzarinif, ADS International
The Large Binocular Camera (LBC) is the double optical imager that will be installed at the prime foci of the Large Binocular Telescope (2x8.4 m) . Four italian observatories are cooperating in this project: Rome (CCD Camera), Arcetri-Padua (Optical Corrector) and Trieste (Software). LBC is composed by two separated large field (27 arcmin FOV) cameras, one optimized for the UBV bands and the second for the VRIZ bands. An optical corrector balances the aberrations induced by the fast (F#=1.14) parabolic primary mirror of LBT, assuring that the 80% of the PSF encircled energy falls inside one pixel for more of the 90% of the field. Each corrector uses six lenses with the first having a diameter of 80cm and the third with an aspherical surface. Two filter wheels allow the use of 8 filters. The two channels have similar optical designs satisfying the same requirements, but differ in the lens glasses: fused silica for the "blue" arm and BK7 for the "red" one. The two focal plane cameras use an array of four 4290 chips (4.5x2 K) provided by Marconi optimized for the maximum quantum efficiency (85%) in each channel. The sampling is 0.23 arcseconds/pixel. The arrays are cooled by LN2 cryostats assuring 24 hours of operation. Here we present a description of the project and its current status including a report about the Blue camera and its laboratory tests. This instrument is planned to be the first light instrument of LBT.
Conference 4848: Advanced Telescope and Instrumentation Control Software II
[4848-43] LUCIFER control software: an OO approach using CORBA technology
Jütte, Marcus; Polsterer, Kai; Lehmitz, Michael; Dettmar, Ralf-Jürgen, Astronomisches Institut der Ruhr-Universität Bochum
n this paper we present the design of the control software for the LBT NIR spectroscopic Utility with Camera and Integral-Field unit for Extragalactic Research (LUCIFER) which is one of the first-light instruments for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona. The LBT will be equipped with two identical LUCIFER instruments for both mirrors. Furthermore we give an overview of the intended hardware structure of the instrument. Since the project requires a detailed and exact modeling of the software we present UML diagrams starting with an overall model down to use case, activity and class diagrams including an example for one special instrument unit.