[ASA] News from GMTO

John O'Byrne john.obyrne at sydney.edu.au
Thu Nov 14 16:37:16 AEDT 2013

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Third GMT Primary Mirror Segment Cast

Edward "Rocky" Kolb delivers his keynote speech

In late August, the third GMT primary mirror segment was successfully cast in the rotating furnace beneath Wildcat Stadium at the University of Arizona. Nearly 20 tons of low-expansion glass was heated to the melting point, some 2100 F˚. While the furnace and honeycomb mold spun at 4.5 rpm, the molten glass flowed into the complex ceramic mold and settled into the approximate shape of the final mirror.

GMTO and the University of Arizona hosted three days of events around the mirror casting, culminating in a gala dinner at the La Paloma resort in the Tucson foothills. At the reception GMTO Board Member Edward "Rocky" W. Kolb described the construction of the world's first nuclear reactor under University of Chicago's original football stadium - Stagg Field. 

Dae Wook Kim explains the polishing process to Steward Observatory Mirror Lab visitors

Kolb, the University of Chicago's Dean of Physical Sciences, compared the 1942 technological advancement to the impressive work being done in the Steward Observatory Mirror Lab, which resides under the east wing of the University of Arizona football stadium.

Kolb's message: Important scientific breakthroughs take place under, rather than on, football fields. 

More ...
A Distinguished Scientist Returns to the GMT Project

Rebecca Bernstein, GMT Project Scientist
GMTO recently announced the appointment of Rebecca A. Bernstein as GMT Project Scientist. She joined the organization on November 1st to provide technical and scientific leadership for the design and construction of the Giant Magellan Telescope. 

For someone who only recently moved into her office, Bernstein already knows a lot about the Giant Magellan project. While at the University of Michigan she was a member of the core design team that developed the original concept for the GMT. Indeed, Bernstein's appointment as Project Scientist
 - and her move to Pasadena - is more of a homecoming than a new arrival.

After earning a B.S. in physics from Princeton University and a Ph.D. in astrophysics from the California Institute of Technology, Bernstein took a prestigious NASA Hubble Postdoctoral Fellowship to the Carnegie Institution for Science.  "I lived in Pasadena longer than I've lived anywhere since I graduated from high school.  It definitely still feels like home."
More ...
GMT's Adaptive Optics System Passes Major Milestone 

Rendering of the Adaptive Secondary Mirror mounted on thetop end frame of the telescope. Three segments are shown in cross-section, revealing some of the 4,704 electromagnetic actuators and the thin glass face sheets they support.
Giant Magellan's Adaptive Optics system is one of the telescope's most complex components. The system passed its Preliminary Design Review in July when an external panel of international experts gave the team a strong endorsement. Keith Raybould, GMT Project Manager, reports that the panel pronounced the AO system ready to proceed to the next level of development, and that they felt that all major technical risks have been addressed.
The effect of the Earth's atmosphere on ground-based observation of distant objects is witnessed in the twinkling of stars. Light rays traveling to the Earth's surface from a distant object are distorted by the temperature and density inhomogeneities in the atmosphere. It's comparable to a large crowd of people (the incoming light rays) all trying to cross a busy street (the atmosphere). Even if they all start crossing at the same time, they won't all reach the other side together, as some slow down and others speed up to avoid the passing traffic.
As a consequence, images taken through the atmosphere are typically blurred by about 1 arcsecond, the size of a quarter seen from 3 miles (5 km) away. Finer details in astronomical objects cannot be distinguished without correcting for these atmospheric effects.

To overcome this obstacle, the Giant Magellan Telescope will make use of a technology known as Adaptive Optics. 

More ...

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