June 9, 2010

TMT OBSERVATORY CORP.

A rendering of the Thirty Meter Telescope.

Dynamic Structures sees steel in a different light

PETER KENTER

correspondent

Most successful steel fabricators have a vision that extends to the future. As the foremost designer and builder of observatory telescopes, Coquitlam, British Columbia-based Dynamic Structures Ltd. has a vision that extends light years.

Known also for building traditional steel structures, such as bridges, and amusement park rides, the company’s latest astronomy project is the Thirty Meter Telescope (TMT), the largest optical telescope ever built, with sensitivity almost 100 times greater than existing telescopes.

The designation describes the size of the telescope’s circular mirror reflector, which will measure 30 metres across.

In turn, the large reflector is made up of many smaller mirrors.

When completed, the $990-million project will stand in an observatory 22 storeys tall, located on the Big Island of Hawaii atop inactive volcano Mauna Kea.

TMT OBSERVATORY CORP.

Another rendering of the Thirty Meter Telescope.

The TMT is a joint Canada-U.S. venture headed up by the Associated Canadian Universities for Research in Astronomy, the University of California, and the California Institute of Technology.

The project started in 2004 and is expected to see first light by 2018.

Smaller projects generally operate on a three-year cycle: a year to design, a year to fabricate and a year to build, said David Halliday, president and director of special projects with Dynamic Structures.

“The challenge with developing this sort of project is knowing when to stop designing it,” he said.

“When you’re pushing the frontiers of technology, you can reconfigure the whole design of the telescope three or four times to satisfy the newest technology. We’ve now finalized the design so we can fabricate it.”

The telescope will employ an advanced application of adaptive optics, which uses lasers to create an artificial star to map optical aberrations caused by Earth’s atmosphere.

The reflectors will be connected to 3,000 actuators that will alter the shape of the mirror hundreds of times per second, reshaping light waves as they enter the telescope to compensate for optical turbulence.

“The system is trying to make the telescope believe that the atmosphere isn’t there,” said Halliday.

“Using this system, ground-based astronomy will achieve image quality better than the Hubble Space Telescope.

“However, as the need for precision increases, so does the requirement for the components to remain stiff because you can’t correct for frequencies below a certain level. But, making very stiff structures also means making them heavier.”

The TMT also features a new design for the telescope enclosure, which protects the telescope both from temperature variations and winds.

Traditional telescope enclosures use a slot design in an irregular dome.

Unfortunately, as telescopes grow larger, the cost of building can rise exponentially.

The TMT is designed with a spherical enclosure and a circular aperture that matches the reflector’s field of view, minimizing the exposure of the reflector to outside elements, limiting the number of moving parts and reducing the weight of the enclosure.

“We’ve demonstrated it will work and got everyone to buy into the risk,” said Halliday. “With this system, we have the enclosure size down by between 2,000 and 4,000 tonnes to only 1,500 tonnes.”

Once the metal components—including 4,000 insulated roof panels—are fabricated in Canada, they’ll be shipped to Hawaii and construction will begin.

Assembly will take place over a three-year period using a crew of up to 100.

Technical and management staff will primarily be drawn from Dynamic Structures with much of the construction labour hired from Hawaii and the mainland.

“One of the construction challenges is working in the hostile environment at 14,000 feet,” said Halliday.

“The health of the workers is extremely important and all of the individuals who work on the project are medically tested beforehand.”

Dynamic Structures designed and built its first high-altitude enclosure, for the Canada-France-Hawaii Telescope, on Mauna Kea in 1979.

The company also assumed the contract for the telescope assembly, which had begun in France.

Since then they have built two Gemini enclosures, Mauna Kea and in Chile, the Sir William Herschel and the Sir Isaac Newton Telescope Enclosures in the Canary Islands, and the W. M. Keck Telescope Enclosure and the W.M. Keck II Telescope on Mauna Kea, among others.

Halliday noted the unglamorous moniker of Thirty Meter Telescope is temporary.

“When they dedicate it, they’ll name it after an astronomer like William Herschel—or someone else they can honour,” he said.

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