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Hubble’s replacement put to the test

THE MANY COMPONENTS of the James Webb Space Telescope undergo testing at their place of construction, as well as at the locations where the individual pieces are assembled into larger parts.

But closer to launch, engineers need to put the fully assembled telescope through environmental testing.

NASA will be using its largest thermal vacuum chamber to accomplish this task. The chamber at Houston’s Johnson Space Centre was used to test Apollo vehicles back in the ’60s and ’70s, and has been used sporadically throughout the following years for other space vehicles.

Changes are being made to the chamber so the James Webb Space Telescope can be tested even more rigorously than the Apollo spacecraft.

Adapted from information issued by Space Telescope Science Institute.

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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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Space umbrella to protect new telescope

LIKE A BEACH UMBRELLA protects people from the Sun’s heat and ultraviolet radiation, the James Webb Space Telescope’s sunshield will protect the telescope and the sensitive infrared instruments from the Sun’s heat and light.

“Each of the five layers of the shield is less than half the thickness of a piece of paper. The five work together to create an effective SPF (or Sun Protection Factor) of 1,000,000,” said John Durning, Deputy Project Manager for the James Webb Space Telescope Project, at NASA’s Goddard Space Flight Centre.

The large sunshield is 20 metres by 12 metres and made of a material called Kapton that can be folded like a blanket. Kapton is a film developed by DuPont which can remain stable and strong over the wide range of temperatures, from 36K to 650 Kelvin (K) (-237 to 377°C), the sunshield will experience during its launch and deployment.

Once on orbit, the sunshield creates a 330 K (117°C to -212°C) temperature differential between the hottest and coldest layers. Using multiple separated layers allows most of a layer’s heat to radiate to space before it reaches the next one, forming a substantial temperature drop from one layer to the next.

Artist's concept of JWST

Artist's concept of the James Webb Space Telescope, showing the five-layer sunshield.

The James Webb Space Telescope will observe primarily the infrared light from faint and very distant objects. But all objects, including telescopes, also emit infrared light in the form of heat energy. To avoid swamping the very faint astronomical signals with radiation from the telescope and the telescope from seeing its own thermal signature, the telescope and its instruments must be very cold, at an operating temperature of under -223°C.

The observatory will be pointed so that the Sun, Earth and Moon are always on one side, and the sunshield will act like a beach umbrella, keeping the Optical Telescope Element and the Integrated Science Instrument Module on the telescope’s topside cool by keeping them in the shade and protecting them from the heat of the Sun and warm spacecraft electronics.

The Webb telescope will orbit 1,513,000 km from Earth at the L2 Lagrange point and will be the first deployable optical telescope in space. It will undergo a complex post-launch sequence of deployments including the sunshield, before it becomes fully operational.

For more information on the sunshield, visit http://www.jwst.nasa.gov/sunshield.html

For more information on the James Webb Space Telescope, visit http://jwst.nasa.gov/

Adapted from information issued by Rob Gutro, NASA’s Goddard Space Flight Centre.

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Model brings telescope to life

It takes many years to build a space telescope or a satellite and years to put one together. However, when it comes to assembling and disassembling the life-sized model of NASA’s James Webb Space Telescope, it takes a handful of days. That’s how long it took to assemble the Webb model in New York City recently.

The full-scale model of the James Webb Space Telescope was built by the prime contractor, Northrop Grumman, to provide a better understanding of the size, scale and complexity of the satellite. It was set up in New York City’s Battery Park for the 2010 World Science Festival, which ran from June 1 to 6.

The life-sized model is made mainly of aluminium and steel, weighs 5.4 tonnes, and is approximately 24 metres long, 12 metres wide and 12 metres tall. It was specifically designed for an environment subject to gravity and weather. It takes two trucks to ship the model over land, and assembly takes a crew of 12 approximately four days.

The following video gives an overview of the mission of the James Webb Space Telescope:

More information:

NASA’s James Webb Space Telescope

Photos of the full-scale model

Adapted from information issued by NASA / Rob Gutro / Mike McClare.

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Coming soon: Hubble’s successor

The Webb Telescope 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.

Comparison of Hubble and Webb primary mirrors

The Webb Telescope's segmented mirror system will be almost three times as big as Hubble's mirror.

Originally known as the “Next Generation Space Telescope” (NGST) and considered the successor to the Hubble Space Telescope, the telescope was renamed in September 2002 after former NASA administrator, James Webb.

More information about the Webb Telescope

Adapted from information issued by NASA.

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