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LBT Project Overview
Project Organization
Project Status
Technical Description
Version:
31 August 2002
| LBT Project
Overview |
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The Large Binocular Telescope
(LBT) is
a collaboration between the Italian astronomical community
(represented by the Instituto Nazionale di Astrofisica (INAF)),
The University of Arizona,
Arizona State University, Northern
Arizona University, the LBT
Beteiligungsgesellschaft in Germany (Max-Planck-Institutfür
Astronomie in Heidelberg,
Landessternwarte in Heidelberg,
Astrophysikalisches Institut in Potsdam,
Max-Planck-Institut für Extraterrestrische Physik in Munich, and
Max-Planck-Institut für Radioastronomie in Bonn),
The Ohio State University,
Research Corporation in Tucson, and the
University of Notre Dame. The goal of the LBT project is to
construct a binocular telescope consisting of two 8.4-meter mirrors
on a common mount. This telescope will be equivalent in
light-gathering power to a single 11.8 meter instrument. Because of
its binocular arrangement, the telescope will have a resolving power
(ultimate image sharpness) corresponding to a 22.8-meter telescope.
The feasibility study for the project was completed in early 1989.
In 1992, the original partners (Arizona, Italy and Research
Corporation) decided to proceed to the construction phase even
though the funds available were sufficient only to complete a
"reduced first light" telescope with only one primary mirror in
place. With the addition of LBTB and Ohio State University to the
consortium in 1997, the project began to construct the full
binocular telescope. The telescope was completed in Italy and
shipped to Arizona in the summer of 2002. |
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Project Organization |
| The Large Binocular Telescope Corporation was established
in 1992 to undertake the construction and operation of the LBT.
The LBT Corporation Board of Directors oversees the project, which
currently includes two representatives from Arizona, Italy, and
LBTB, and one representative from Ohio and Research Corporation. |
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The LBT Corporation maintains one Corporate Office
and two Project Offices. The Corporate Office is located in Tucson,
Arizona. It handles the financial management of the corporation
and the communications with board members. |
| The two Project Offices are located in Tucson,
Arizona and in Arcetri, Italy. The Project Offices oversee the design
and construction activities of the telescope. |
Project Office Contact
Information
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LBT Project Office/Tucson |
LBT Project Office/Arcetri |
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Steward Observatory
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The University of Arizona
- Tucson, AZ 85721-0065
- TELEPHONE: 520 626-5231
- TELEFAX: 520 626-9333
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- Osservatorio Astrofisico di Arcetri
- Largo Enrico Fermi, 5
- 50125 Firenze, ITALY
- TELEPHONE: 011 39 055 2752291
- TELEFAX: 011 39 055 225319
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The LBT Project Office in Tucson coordinates contractual
agreements and financial functions.
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Project Status |
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Telescope
Site
Primary Mirror
Enclosure
Optics
Aluminizing Facility
Funding
First Light
Important Links |
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Telescope |
| A contract for the detailed mechanical design of
the telescope was signed in April of 1994 with a Consortium formed
by the Italian engineering firms of ADS International (Lecco) and
European Industrial Engineering (Mestre). The two companies provided
quality assurance monitoring during the manufacturing, assembling,
and testing of the various sub-systems as well as during the telescope
pre-erection in the workshop. In January 1998, a contract was awarded
to Ansaldo Energia S.p.A. (Milan) for the fabrication and factory
pre-erection of the main structure of the telescope. The telescope
was shipped to Arizona in mid-2002. The Hydrostatic Bearing System
and Gears for the telescope were manufactured by Tomelleri S.r.l.
in Verona, Italy. |
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Site |
| The Large Binocular Telescope is part of the Mt.
Graham International Observatory near Safford, Arizona. The
construction of the observatory with three telescopes was approved
by Congress in November 1988. During the 1996
construction season, the site for the LBT telescope on Emerald Peak
was cleared of trees and rocks and a retaining wall was erected
along the northeast side. Geological surveys were performed to identify
the best location for the telescope pier, and the foundation was
poured just before the arrival of inclement weather. During the
1997
season, the telescope pier and ring wall that supports the rail
of the rotating upper part of the enclosure were constructed. Steel
for the lower portion of the enclosure was erected, and the 200-meter
utility trench was begun. The 1998
season included the erection of the rail and bogies, the rotating
building structure, and cladding of the lower enclosure. The 1999
season included completion and cladding of the rotating building
structure, installation of the pier cap and the completion of the
utility trench. Contracts for enclosure completion packages (architectural
finishing, HVAC and plumbing mechanisms, and electrical systems
and controls) were signed and work began in 1999. The enclosure
was completed by the end of 2002. |
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Primary Mirror |
| Contracts for the fabrication and polishing of
the two 8.4- meter primary mirrors are in place with The University
of Arizona Steward Observatory Mirror
Lab. The Lab has already successfully cast and polished three
6.5-meter honeycomb mirrors in its program of casting large mirrors.
Casting of the first 8.4 meter honeycomb mirror took place in mid-January
1997. The mirror underwent a slow annealing and cooling process
and was inspected in early April confirming that the leakage of
glass noted during the casting resulted in some thinning of the
mirror's faceplate. An area consisting of approximately 10% of the
total surface of the mirror was at a less than optimum thickness.
Two tons of glass were added to the mold in late April and a slow
heating process was started. The faceplate was remelted in June,
and the mirror was annealed and cooled during the summer. In September
1997, the furnace was opened to reveal a 100% successful casting.
The mirror was lifted in February 1998, and the mold material has
been washed out. Finishing of the back side of this mirror was completed
in June 1999. Casting of the second primary mirror took place in
May 2000. With additional tension on the Inconel bands, no glass
leaks occurred during this casting. As of August 2002, the first
mirror is being polished and the second mirror is being cleaned
out.
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Enclosure |
| The detailed architectural design of the enclosure
was done by a Consortium of companies headed by M3
Engineering & Technology Corp (M3). M3 has already designed
many telescope enclosures including others on Mt.
Graham, and has been able to provide the necessary knowledge
on the local building codes and regulations. ADS (also part of the
Consortium) provided continuity in the enclosure design evolution
since it has been working on the project since 1985. ADS and EIE
were charged with assuring the correct interface between the enclosure
and the telescope design contract. Hart Construction Management
Services of Safford, Arizona is the General Contractor. |
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Optics |
| Substantial progress has been made at the Steward
Observatory Mirror Lab on a facility to both polish and test secondary
mirrors. Polishing of the Sloan Digital Sky Survey convex secondary
was completed in October 1996. The MMT F/9 secondary was aspherized
in the fall of 1996 and the MMT F/5 was aspherized in 1997. The
MMT F/9 secondary completed final polishing with the stressed lap
in 1998. The MMT F/15 adaptive shell completed final polishing in
1999. The 2.5-meter illuminator mirror to be used for testing the
LBT F/4 and MMT F/5 secondaries has been purchased and was polished
by Rayleigh Optical. |
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Aluminizing Facility |
| ADS International finished the final design for
the bell jar to be used during the aluminizing process of the primary
mirrors. A contract for the fabrication of the bell jar along with
the mirror cells was awarded to Ansaldo Energia S.p.A. in January
1998. Integration of the bell jar will be carried out at The Ohio
State University. |
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Funding |
| The partners: The University of Arizona, INAF,
the LBT Beteiligungsgesellschaft, The Ohio State University and
Research Corporation have committed sufficient funds, $87,800,000
($1998), to permit construction of the complete telescope and enclosure
with two sets of optics and instrumentation. The project is proceeding
with construction on that basis. |
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First Light |
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Current schedules for the telescope, mirror and enclosure
suggest that first light will occur in the spring of 2005.
The second primary should follow approximately 1 year later. |
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Important Links |
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Technical Description |
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Optics
Telescope Structure
Telescope Enclosure
Instruments |
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1 - Optics |
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The telescope will use two 8.408 meter, F/1.142
primaries to provide a collecting area equivalent to an 11.8 meter
circular aperture. Included in the $88.8 million budget are the
costs for two adaptive F/15 secondaries. Other focal stations and
features considered scientifically important for future expansions
will be included in the optical and mechanical design of the telescope
but not initially implemented. |
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Primary Mirrors |
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The two parabolic primary mirrors have been fabricated
at the Mirror Laboratory located in the campus of The University
of Arizona in Tucson, Arizona. Each of the F/1.142 honeycomb borosilicate
mirrors weighs approximately 16 metric tons and was made utilizing
E6 glass manufactured by Ohara
in Japan. The finished mirror diameter is 8.417 meters.
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Focal Stations |
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2 - Telescope
Structure |
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The telescope is an elevation over an azimuth mounting.
The optical support structure moves on two large C-shaped rings
and the compact azimuth frame transmits the loads directly down
to the pier. The two 8.4 meter (331 inch) diameter primary mirrors
are mounted with a 14.4-meter center-center separation. By using
swing arms to rotate the secondary and tertiary mirrors and their
supports, it is possible to switch the telescope from one mode of
observation to another very quickly. The short focal length of the
primary mirrors (F/1.14) permits a compact, and therefore quite
stiff telescope structure.
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3 - Telescope Enclosure |
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design has been driven by the following requirements.
Various combinations on these requirements resulted in
convergence on the concept described below: |
- Protect the telescope from the elements
- M
inimize
the degradation of the site
- Allow for efficient operation and service
- Minimize the cost of the enclosure
- Avoid disruption of the environment
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Following are some of the major design features
of the LBT project enclosure design. |
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Corotating Box |
| The basic design of the building is a corotating
box around the telescope that sits on a circular pier. The structural
steel was fabricated and erected by Schuff Steel in Phoenix, AZ.
Siding for the rotating building was installed by EMCO of Sacramento,
CA. |
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Building Pier |
| The rotating building rides on a 23-meter diameter
circular rail held above the ground by a reinforced concrete wall.
The rail was manufactured by Fravit S.r.l. in Lecco, Italy, and
was installed in spring, 1998. The four bogies that ride on this
rail were manufactured by Costameccanica S.p.A. in Lecco, Italy. |
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Shutters |
| Each aperture of the binocular telescope has a
10.4-meter wide aperture for viewing. These two apertures are covered
by sliding shutters which move apart laterally to open the slits.
Additional openings on the back and sides allow wind ventilation
to flush the building. When the wind is strong, a windscreen can
be raised to protect the telescope from buffeting. |
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55 ton crane |
| A 55-ton crane will allow handling of large equipment
through a 4x10 meter hatch in the telescope floor. Both the aluminizing
bell jar and the mirror cleaning system will be transferred from
the floor of the auxiliary building to the telescope floor through
the hatch. A second crane is available to handle equipment at ground
level. These cranes were manufactured by Lario Impianti S.r.l. in
Osnago, Italy. |
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Fixed building |
| The main telescope building will house all the
machinery and equipment needed to operate the telescope, the control
rooms for the astronomers and some living quarters. |
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Auxiliary building |
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An auxiliary building will surround the telescope
from the northwest to the northeast side. It will provide space
for the optical, electrical and mechanical laboratories where astronomical
instrumentation can be readied and repaired if necessary. The bell
jar and the aluminizing equipment will also be stored there.
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Elevators |
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elevator, located inside the telescope pier, provides access
to the various fixed levels and the transfer floor to the
rotating building. A second elevator in the rotating building
will provide access to the various levels of the telescope.
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4 - Instruments |
| The LBT Scientific Advisory Committee (SAC) has
developed the following list of observational priorities (in no
particular order) to guide the telescope design. |
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Interferometric Imaging |
0.4 to 400 microns |
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Infrared Imaging / Photometry |
2.0 to 30 microns |
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Wide Field Multi-object Spectroscopy |
0.3 to 1.6 microns |
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Faint Object / Long Slit Spectroscopy |
0.3 to 30 microns |
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High Resolution Spectroscopy |
0.3 to 30 microns |
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The SAC envisions the following list of facility
instruments, which will be implemented on the baseline telescope.
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Interferometric imager
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Faint object optical spectrograph
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Near infrared camera and spectrograph
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