NASA's next huge space telescope passed a major mirror milestone this week on its path to become the world's most powerful space observatory when it launches in 2018.
Engineers completed coating 21 mirrors that will make up NASA's flagship James Webb Space Telescope with the thin — but vital — layer of gold that will reflect the faint infrared light collected by the observatory from the most distant reaches of the universe.
John Mather, the telescope's senior project scientist, told SPACE.com.
"It represents not just the coating event but the completion of a huge engineering project. The mirrors are spectacularly new technology."
Each of the 21 hexagonal mirror segments is almost the height of a person (4.9-feet, or 1.5 meters tall) and is made of beryllium, a material chosen for its light weight, stiffness and ability to withstand huge changes in temperature without warping.
Eighteen of the segments will be combined into one giant 21.3-foot (6.5-meter) tall primary mirror. The remaining three mirrors will be used elsewhere in the telescope, NASA officials said.
In June 2010, engineers began the process of coating each mirror with about 0.12 ounces of gold, applied in layers only 120 nanometers thick — about a millionth of an inch, or 200 times thinner than a human hair.
Ian Stevenson, director of coating at Quantum Coating, Inc., the subcontractor responsible for the mirror coating process, said in a statement.
"We faced many technical challenges on the Webb mirror coating program. One of the most daunting was that all flight hardware runs had to be executed without a single failure."
To coat the mirrors, gold was heated to more than 2,500 degrees Fahrenheit (1,371 degrees Celsius), at which point it melted from solid to liquid. Then, engineers allowed it to evaporate onto the beryllium panels to build up the smooth, microscopically thin layer of coating.
Completing this process is a triumph for the beleaguered Webb telescope project, which has been delayed repeatedly and seen its costs rise significantly. The observatory, a joint venture of NASA, the European Space Agency and the Canadian Space Agency, is named after former NASA administrator James Webb, who ushered the agency through most of the Apollo era.
The cost for the telescope is now estimated at $8.7 billion. Because of the project's budget overruns and delays, a House Appropriations Committee spending bill in July proposed to cancel the mission. A Senate subcommittee measure approved Sept. 14, however, would provide enough money to continue the project.
Lee Feinberg, NASA Optical Telescope Element manager for the Webb telescope at the agency’s Goddard Space Flight Center in Greenbelt, Md., said in a statement.
"Finishing all mirror coatings on schedule is another major success story for the Webb telescope mirrors. These coatings easily meet their specifications, ensuring even more scientific discovery potential for the Webb telescope."
COMMENTARY: In spite of its incredible cost, the James Webb Space Telescope is going to be quite an incredible telescope once it is completed and is launched into outer space. The dimensions of the mirrors, the gold coating and challenges to manufacturer each mirror is incredible. I can hardly wait to see what wonderous things and space mysteries it unlocks once this huge new space telescope discovers.
Here are a few videos of the James Webb Space Telescope:
To give you an idea of the scale of the James Webb Space Telescope, here is a comparison with the Hubble Space Telescope:
We are all familiar with the Hubble Space Telescope, but if you are not, here's an excellent video so that you can learn about the differences between both telescopes:
Courtesy of an article dated September 16, 2011 appearing in Space.com and NASA The James Webb Space Telescope
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