OEM Report: Aerospace
Monday | 26 October, 2009 | 8:09 am

Mirror images

By Abbe Miller

October 2009 - Without fail, NASA posts a new picture on its Astronomy Picture of the Day Web site, every day of every week. The images are of celestial formations both beautiful to behold and difficult to comprehend. And visiting the visually amazing Web site is made possible thanks to the telescopes NASA has been engineering and developing for several decades. The James Webb Space Telescope, the newest addition to the NASA fleet, being constructed by Northrop Grumman Corp., Los Angeles, will be launched in 2014. Currently, the construction of its 21.3-ft.-diameter mirror is of particular interest.

The rigors of space
Space telescopes are destined to encounter extremely low temperatures, so the material they're made from must be able to endure that type of frigid environment. And part of a space telescope's job description is to encounter the unknown. Unforeseen conditions require it to be rugged, as well. The James Webb Space Telescope will don 18 mirrors to capture the magnificence of outer space. Each hexagonal segment will be made of beryllium, a material that's not only lightweight, but also strong and able to hold its composure under a wide range of temperatures. It has one of the highest melting points in the family of light metals.

But melting isn't necessarily a concern for the telescope. It's purported that it will experience temperatures as low as -240 degrees Celsius, which beryllium can withstand.

Making the mirrors
According to an article by Rob Gutro from NASA's Goddard Space Flight Center, Greenbelt, Md., "The beryllium being used to make the Webb Telescope's mirrors was mined in Utah and then purified. The particular type of beryllium used in the Webb mirrors is called O-30 and is a fine powder of high purity. The powder is then placed into a stainless steel canister and pressed into a flat shape. The steel canister is then removed, and the resulting chunk of beryllium is cut in half to make two mirror blanks about 1.3 m (4 ft.) across. Each mirror blank will be used to make one mirror segment; the full Webb mirror will be made from 18 hexagonal (six-sided) segments."

He continues to explain that once the mirror blanks are inspected, they will be molded into a final shape. From there, they will be polished and temperature tested.

And by 2014, they will undoubtedly be contributing to NASA's picture of the day, further captivating visitors young and old with pictures from places beyond their normal reach. MM

Originally posted on our sister Web site

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