Project Overview | Project Organization | Project Status | Technical Description
LBT Project Overview
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, Leibniz Institute for Astrophysics inPotsdam,
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.
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.
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
LBT Project Office/Tucson
Steward Observatory, The University of Arizona
Tucson, AZ 85721-0065
TELEPHONE: 520 626-5231
FAX: 520 626-9333
LBT Project Office/Arcetri
Osservatorio Astrofisico di Arcetri
Largo Enrico Fermi, 5
50125 Firenze, Italy
TELEPHONE: +39 055 2752291
FAX: 011 39 055 225319
The LBT Project Office in Tucson coordinates contractual agreements and financial functions.
Project Status
Site | Primary Mirror | Enclosure | Optics | Aluminizing | Funding | First Light
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.
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.
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.
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.
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.
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.
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.
First Light
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.
Technical Description
Optics | Telescope Structure | Telescope Enclosure | Instruments
1. Optics
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.
Primary Mirrors
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.
Focal Station
The principal focal stations of the telescope will be:
a. infrared, dual F/15, Gregorian
b. phased combined, re-imaged F/15, center
2. Telescope Structure
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.
3. Telescope Enclosure
The enclosure 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
* Minimize the degradation of the site
* Allow for efficient operation and service
* Minimize the cost of the enclosure
* Avoid disruption of the environment
Following are some of the major design features of the LBT project enclosure
design:
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.
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.
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.
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.
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.
Auxiliary building
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.
Elevators
An 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.
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:
* Interferometric Imaging: 0.4 to 400 microns
* Infrared Imaging / Photometry: 2.0 to 30 microns
* Wide Field Multi-object Spectroscopy: 0.3 to 1.6 microns
* Faint Object / Long Slit Spectroscopy: 0.3 to 30 microns
* High Resolution Spectroscopy: 0.3 to 30 microns
The SAC envisions the following list of facility instruments, which will be
implemented on the baseline telescope:
* Interferometric imager
* Faint object optical spectrograph
* Near infrared camera and spectrograph