UA Mirror Lab to Cast First Mirror for Giant Magellan Telescope

UA MIRROR LAB TO CAST FIRST MIRROR FOR GIANT MAGELLAN TELESCOPE
From Lori Stiles, UA News Services, 520-621-1877
December 13, 2004


The University of Arizona Steward Observatory Mirror Laboratory and
the
Carnegie Observatories of the Carnegie Institution have signed an
agreement
to produce the first mirror segment for the Giant Magellan Telescope
(GMT),
a project of the multi-institutional GMT consortium.

The Steward Observatory Mirror Lab in Tucson, Ariz., will cast the
27-foot
(8.4-meter) mirror next summer, in 2005.

The GMT will be located at the Carnegie Observatories' site at Las
Campanas, Chile.

The eight partners in the GMT project consortium are the Carnegie
Observatories, the University of Arizona, Harvard University,
Smithsonian
Astrophysical Observatory, University of Michigan, Massachusetts
Institute
of Technology, University of Texas at Austin, and Texas A & M
University.

"The National Academy of Sciences? astronomy decadal survey has
ranked
extremely large telescopes as the highest priority for ground-based
optical
astronomy," Steward Observatory Mirror Laboratory Director and
Regents?
Professor J. Roger P. Angel said. "The GMT is the first of this
next-generation, which is several times larger than the current
generation
of large telescopes, to begin construction of the primary mirror
optics."

--------------------------------------------------------
Contact Information
J. Roger P. Angel 520-621-6541
Peter A. Strittmatter 520-621-6524

Related Web site -- http://www.gmto.org/
---------------------------------------------------------

The GMT?s primary mirror will consist of seven large mirror
segments, each
27 feet (8.4 meters) in diameter. The mirror to be cast next summer
will be
the first of six identical outer segments that will be arranged in a
hexagon
around the seventh, central element. Together they will bring light to
a
focus much as a single mirror 70 feet (21.4 meter) in diameter ?
roughly as
wide as the 2004 Christmas tree in New York?s Rockefeller Center is
tall.

When corrected for atmospheric blurring with adaptive optics, the
telescope
will make infrared images ten times sharper than the Hubble Space
Telescope,
the same as a single 83-foot (25.4 meter) mirror in space.

"The GMT builds on concepts and technologies developed for the Large
Binocular Telescope (LBT), which is approaching completion on Mount
Graham,"
Steward Observatory Director and Regents' Professor Peter Strittmatter
said.

"With its seven 8.4-meter mirrors, the GMT will provide a major
advance in
light-gathering power along with superb optical properties for
high-resolution imaging of very faint objects. The GMT will be a huge
advance for astronomy worldwide, and it's great to see the project get
under
way. We at the UA are proud to be partners in this epoch-making
project."

The GMT, scheduled for completion in 2016, will be able to probe the
secrets of planets that have formed around other stars in the Milky
Way,
peer back in time toward the Big Bang with unprecedented clarity, delve
into
the nature of dark matter and dark energy, and explore the formation of
black holes. These rank among the most important questions in astronomy
today.

The GMT capitalizes on the technology base that UA Steward Observatory
and
collaborating institutions have developed for a series of
current-generation
large telescopes: the MMT in southern Arizona, twin Magellan telescopes
in
Chile, and the Large Binocular Telescope on Mount Graham, Ariz.

The GMT will use the lightweight, honeycombed borosilicate primary
mirrors
for which the Mirror Lab is famous. Six GMT primary mirror segments
will be
off axis, that is, they'll focus light at an angle so it merges with
light
focused by the on-axis central mirror.

"The net effect is that the GMT will appear to have a single 26-meter
mirror covered with a mask consisting of seven 8.4-meter apertures,"
Strittmatter said. "Fabricating the off-axis mirrors is the new element
in
the program, and this first GMT mirror will serve to demonstrate the
technology at the 8.4-meter scale."

In preparation for making the GMT mirror, a Mirror Lab team headed by
Buddy
Martin already is working on a 5.5-foot (1.7 meter) off-axis aspheric
primary mirror, a one-fifth scale GMT mirror fabrication demonstration
that
will be used for the New Solar Telescope at Big Bear Observatory.

The GMT will incorporate other advanced technologies pioneered by
Steward
Observatory and collaborating researchers in Italy. Its adaptive optics
system -- a system that compensates for light blurring in Earth's
atmosphere
? will be directly integrated into the telescope optics. The
deformable
secondary mirror will make the correction.

The nearly 10-foot (3 meter) diameter secondary mirror will be
electro-magnetically gripped by thousands of computer-controlled
'actuators'
that tweak the mirror with nanometer precision. The unique system has
been
pioneered at the MMT and also is being incorporated in the LBT.

Researchers at Steward Observatory also are developing a tomographic
system
to measure atmospheric blurring.

"The Giant Magellan Telescope will allow an unprecedented view of
extrasolar planets, as well as a window out to the largest scales and
back
to the earliest moments in the universe," Wendy Freeman, director of
the
Carnegie Observatories, said. "We plan to complete the GMT so that it
will
work in tandem with the future generation of planned ground- and
space-based
telescopes.

"The real distinction of GMT, however, is that it is building on a
heritage
of successful technology," Freeman added. The performance of the twin
Magellan telescopes at Las Campanas "has far exceeded our
expectations," she
said.

Detailed information about the design of the GMT and the science that
it
will perform is on the Web at http://www.gmto.org/