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Hubble’s successor passes milestone

NASA engineer looks at first six flight ready James Webb Space Telescope's primary mirror segments

NASA engineer Ernie Wright looks on as the first six flight-ready James Webb Space Telescope's primary mirror segments are prepped to begin final freeze testing at NASA's Marshall Space Flight Centre.

MIRRORS ARE THE MOST CRITICAL PART of a telescope. Quality is crucial, so completion of mirror polishing represents a major milestone. All of the mirrors that will fly aboard NASA’s James Webb Space Telescope have now been polished so the observatory can see objects as far away as the first galaxies in the universe.

The Webb telescope has four types of mirrors. The primary one has an area of approximately 25 square metres, made up of 18 separate mirrors, which will enable scientists to capture light from faint, distant objects in the universe faster than any previous space observatory.

The mirrors are made of the light metal Beryllium and will work together to relay images of the sky to the telescope’s science cameras.

“Webb’s mirror polishing always was considered the most challenging and important technological milestone in the manufacture of the telescope, so this is a hugely significant accomplishment,” said Lee Feinberg, Webb Optical Telescope manager at NASA’s Goddard Space Flight Centre.

The mirrors were polished at the L3 Integrated Optical Systems–Tinsley in Richmond, California to accuracies of less than one millionth of an inch. That accuracy is important for forming the sharpest images when the mirrors cool to minus 240°C in the cold of space.

Artist's impression of the James Webb Space Telescope

Artist's impression of the James Webb Space Telescope, due for launch later this decade.

New technology invented

“The completion of the mirror polishing shows that the strategy of doing the hardest things first has really paid off,” said Nobel Prize Winner John C. Mather, Webb’s senior project scientist at Goddard. “Some astronomers doubted we could make these mirrors.”

After polishing, the mirrors are being coated with a microscopically thin layer of gold to enable them to efficiently reflect infrared light. NASA has completed coating 13 of 18 primary mirror segments and will complete the rest by early next year. The 18 segments fit together to make one large mirror 6.5 metres across.

“This milestone is the culmination of a decade-long process,” said Scott Willoughby, vice president and Webb Telescope Program manager for Northrop Grumman Aerospace Systems. “We had to invent an entire new mirror technology to give Webb the ability to see back in time.”

As the successor to the Hubble Space Telescope, the Webb telescope is the world’s next-generation space observatory. It is the most powerful space telescope ever built.

More than 75 percent of its hardware is either in production or undergoing testing—the observatory will be launched later this decade.

The telescope will observe the most distant objects in the universe, provide images of the first galaxies ever formed and study planets around distant stars. NASA, the European Space Agency and the Canadian Space Agency are collaborating on this project.

The following video shows what it takes to get the Webb Telescope’s mirrors ready for flight:

Adapted from information issued by Rob Gutro, NASA Goddard Space Flight Centre. Images courtesy NASA / Ball Aerospace / Tinsley; NASA / MSFC / David Higginbotham; STScI / Mary Estacion.

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Chilly test for new space telescope

THE FIRST OF 18 SEGMENTS that will form NASA’s James Webb Space Telescope’s primary mirror for space observations, have completed final cryogenic testing.

The ten-week test series included two tests cycles where the mirrors were chilled down to -228 degrees Celsius, then back to ambient temperature to ensure the mirrors respond as expected to the extreme temperatures of space.

A second set of six mirror assemblies will arrive at Marshall in late July to begin testing, and the final set of six will arrive in the later in 2011.

The X-ray and Cryogenic Facility at NASA’s Marshall Space Flight Centre in Huntsville, Alabama, provides the space-like environment to help engineers measure how well the telescope will image infrared sources once in orbit.

Engineers and technicians with some of the JWST's mirror segments

Engineers and technicians guide check some of the James Webb Space Telescope’s mirror segments following cryogenic testing.

Each mirror segment measures approximately 1.3 metres in diameter to form the 6.5 metres, hexagonal telescope mirror assembly critical for infrared observations. Each of the 18 hexagonal-shaped mirror assemblies weighs approximately 40 kilograms.

The mirrors are made of a light and strong metal called beryllium, and covered with a microscopically thin coating of gold to enabling the mirror to efficiently collect infrared light.

The NASA’s James Webb Space Telescope is expected to be launched in 2017 or 2018. Placed over 1 million kilometres from Earth, it will observe primarily the infrared light from faint and very distant objects.

It will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of planetary systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

The telescope is a combined project of NASA, the European Space Agency and the Canadian Space Agency. Northrop Grumman is the prime contractor under NASA’s Goddard Space Flight Centre. Ball Aerospace & Technologies Corp. in Boulder, Colorado, is responsible for mirror development. L-3- Tinsley Laboratories Inc. in Richmond, California is responsible for mirror grinding and polishing.

Adapted from information issued by NASA / Emmett Given.

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Amazing telescope video

The European Southern Observatory has telescopes located at several sites in Chile, South America. Prime among them is the Very Large Telescope, or VLT.

The VLT is actually a number of telescopes that can work individually or in concert.

There are the four huge, main telescopes—each with main, or primary, mirrors that are 8.2 metres in diameter—plus several auxiliary telescopes with mirrors 1.8 metres in diameter.

The main mirrors are huge, round pieces of very special glass, carefully formed into shape with a gentle parabolic curve on their surface. Light coming in from space reflects off this curved surface and is brought to a focus.

But the light doesn’t reflect from the glass—it bounces off an extremely thin layer of aluminium that has been deposited on the glass, to give it a shiny, reflective surface.

Over time, this layer becomes tarnished and needs to be removed and replaced. The video above shows what’s involved in this process—and it’s a very involved process indeed!

A longer, utterly fascinating and highly-recommended video (but with no narration) can be found on the ESO web site.

Story by Jonathan Nally, editor SpaceInfo.com.au

Images and video courtesy ESO.

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