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Astronomie - NASA Webb Telescope bekommt seine Gestalt - Update-5

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18.12.2015

James Webb Space Telescope startete mit einer Ariane-5-Rakete von Kourou im Oktober 2018.

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Test mirror segments for the James Webb Space Telescope

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The next great space observatory took a step closer this week when ESA signed the contract with Arianespace that will see the James Webb Space Telescope launched on an Ariane 5 rocket from Europe’s Spaceport in Kourou in October 2018.

Ariane is part of the European contribution to the cooperative mission with NASA and the Canadian Space Agency, along with two of the four state-of-the-art science instruments for infrared observations of the Universe.
The telescope’s wide range of targets includes detecting the first galaxies in the Universe and following their evolution over cosmic time, witnessing the birth of new stars and their planetary systems, and studying planets in our Solar System and around other stars.
With a 6.5 m-diameter telescope, the observatory must be launched folded up inside Ariane’s fairing. The 6.6 tonne craft will begin unfolding shortly after launch, once en route to its operating position some 1.5 million km from Earth on the anti-sunward side.
The contract includes a cleaner fairing and integration facility to avoid contaminating the sensitive telescope optics.
“With this key contract now in place with our long-standing partners, we are closer than ever to seeing the scientific goals of this next-generation space observatory realised,” says Jan Woerner, ESA’s Director General.
“This agreement is a significant milestone,” says Eric Smith, NASA’s JWST programme director. “The years of hard work and excellent collaboration between the NASA, ESA and Arianespace teams that have made this possible are testimony to their dedication to the world’s next great space telescope.”
“It is a great honour for Arianespace to be entrusted with the launch of JWST, a major space observatory which will enable science to make a leap forward in its quest of understanding our Universe,” said Stéphane Israël, Chairman and CEO of Arianespace.
“It is also an immense privilege to be part of such an international endeavour gathering the best of US, European and Canadian space technology and industry.”
JWST’s science module, with all four flight instruments, is undergoing final tests at cryogenic temperatures at NASA’s Goddard Space Flight Center. Assembly of the 18 mirror segments, which will unfold after launch, is also now underway.
“With the launch service agreement formally agreed, and with NASA’s continuing solid progress of integrating and testing JWST, we keep the steady pace towards the launch in October 2018,” says Peter Jensen, ESA’s project manager.
Quelle: ESA
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Update: 28.12.2015
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James Webb Space Telescope Mirror Halfway Complete
Inside NASA's Goddard Space Flight Center's massive clean room in Greenbelt, Maryland, the ninth flight mirror was installed onto the telescope structure with a robotic arm. This marks the halfway completion point for the James Webb Space Telescope's segmented primary mirror.
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This rare overhead shot of the James Webb Space Telescope shows the nine primary flight mirrors installed on the telescope structure in a clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Credits: NASA's Goddard Space Flight Center/Chris Gunn
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The James Webb Space Telescope team has been working tirelessly to install all 18 of Webb's mirror segments onto the telescope structure.
"The years of planning and practicing is really paying dividends and the progress is really rewarding for everyone to see," said NASA's Optical Telescope Element Manager Lee Feinberg.
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Engineers worked tirelessly to install the ninth primary flight mirror onto the telescope structure.
Credits: NASA's Goddard Space Flight Center/Chris Gunn
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In these NASA images, the engineering team is seen using a robotic arm to lift and lower the hexagonal-shaped segment that measures just over 4.2 feet (1.3 meters) across and weighs approximately 88 pounds (40 kilograms). After being pieced together, the 18 primary mirror segments will work together as one large 21.3-foot (6.5-meter) mirror. The full installation is expected to be complete early in 2016.
The mirrors were built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and lightweight mirror system. The installation of the mirrors onto the telescope structure is performed by Harris Corporation of Rochester, New York. Harris Corporation leads integration and testing for the telescope.
The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, ESA (the European Space Agency) and the Canadian Space Agency.
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Nine of the James Webb Space Telescope's 18 primary flight mirrors have been installed on the telescope structure. This marks the halfway point in the James Webb Space Telescope's primary mirror installation.
Quelle: NASA
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Update: 6.01.2016
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Testing the James Webb Space Telescope with Radio Waves
The instruments that will fly aboard NASA's James Webb Space Telescope not only have to be tough enough to survive in the cold of space, but they also have to work properly in the electromagnetic environment on the spacecraft, so they're tested for both. Recently, they passed a test for the latter in a very unique room.
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A team of engineers in special clean room suits at NASA Goddard. Seen from left to right: Andy Mentges, Nathan Block, Vaughn Nelson, Rob Houle, John McCloskey, Mark Branch, Rick Jones, Greg Jamroz.
Credits: NASA/Chris Gunn
Stepping inside NASA's Electromagnetic Interference or EMI laboratory at NASA's Goddard Space Flight Center in Greenbelt, Maryland feels like stepping inside a Lady Gaga music video. Inside this white room where conical structures jut out from the walls, a team of engineers clad in "bunny suits" or white suits recently and successfully completed one of the key environmental tests for the Integrated Science Instrument Module (ISIM), the science payload of the James Webb Space Telescope. 
The ISIM can be considered the eyes and ears of Webb telescope and the purpose of the test was to verify that these eyes and ears will be compatible with the electromagnetic environment on the spacecraft.
Once inside the clean room, the team set up antennae for different tests. Their first task was to measure the electromagnetic emissions from the ISIM in order to assess the likelihood of interference to the rest of the spacecraft. They also illuminated the ISIM with electromagnetic waves in order to assess the likelihood of interference from the rest of the spacecraft.   
These tests must be performed in an anechoic (Latin for “no echo”) chamber. The conical structures jutting out from the walls absorb the electromagnetic energy in order to minimize reflections. As much as a sound booth works to minimize the reflection of sound waves, the anechoic material minimizes reflections of electromagnetic waves so that they don't bounce back and combine with the original waves, which would disturb the integrity of the test.
"The anechoic material minimizes reflections in order to give maximum control of the test," said Goddard Chief EMC Engineer John McCloskey. "A metal wall is like a mirror for electromagnetic waves. These walls are designed to absorb the radiated energy and minimize reflections so that we know what we are actually measuring.  We need to know that what we are measuring is actually coming directly from ISIM and not from multiple reflected paths in the room."
The project schedule allotted 10 days for the test. The team met all the test objectives in 8.5 days. ISIM passed with flying colors.
"Despite a few setbacks, our team finished the test ahead of schedule and beat the deadline," said John McCloskey. "This test is important because when the James Webb Space Telescope is operating in space and identifying distant galaxies and other astronomical objects, we will have confidence that these are indeed real objects and not blips caused by electromagnetic interference."
Now, the ISIM is inside the thermal vacuum chamber at NASA Goddard, undergoing its third and final cryogenic test. This test will ensure that Webb telescope's eyes and ears will work properly in the frigid temperatures of space.
The images from the Webb telescope will reveal the first galaxies forming approximately 13.5 billion years ago. The telescope will also see through interstellar dust clouds to capture stars and planets forming in our own galaxy. At the telescope's final destination in space, one million miles away from Earth, it will operate at incredibly cold temperatures of minus 387 degrees Fahrenheit, or 40 degrees Kelvin. This is 260 degrees Fahrenheit colder than any place on the Earth’s surface has ever been.
The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, the European Space Agency and the Canadian Space Agency.
Quelle: NASA
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Update: 20.01.2015
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JWST's 15th mirror segment officially installed, #16 is in the works!
Quelle: NASA
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Update: 25.01.2016
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Massive Space Telescope Is Finally Coming Together

A NASA team has attached nearly all of the hexagonal segments that will together make the primary mirror for the James Webb Space Telescope (pictured are practice segments).
Chris Gunn/NASA
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This week, NASA is set to reach a milestone on one of its most ambitious projects. If all goes to plan, workers will finish assembling the huge mirror of the James Webb Space Telescope — an $8 billion successor to the famous Hubble telescope.
"So far, everything — knock on wood — is going quite well," says Bill Ochs, the telescope's project manager at Goddard Space Flight Center in Maryland.
The massive mirror is being built in a facility that's essentially a giant, ultra-clean gymnasium. NPR can't go inside for risk of contamination, but I meet crew chief Dave Sime at an observation deck where we can see the mirror below. Sime works for the contractor Harris Corp., and he's normally in there assembling it. When he is, he has to wear a white suit that covers every inch of his body.
"The only thing exposed is your eyes," he says. (Spacecraft assembly pro tip, he adds: To use your cellphone in the clean area, try a Bluetooth headset under your protective clothing.)
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The telescope will consist of 18 mirror segments when it's completed. Each segment can be independently adjusted to bring the starlight into focus.
David Higginbotham/Emmett Given/MSFC/NASA
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For months now, he's been working 10-hour shifts. His job is to take 18 hexagonal mirror segments, each about the size of a coffee table, and attach them to the telescope's cobweb frame using glue and screws.
When everything is done, the mirror will look like a giant, golden satellite dish, two stories high.
The assembly process is precise, and more difficult than even an Ikea wardrobe. Sime points to a table covered in books filled with instructions: "Each one of those notebooks is for one mirror," he says.
Everything has to be by the book. The Webb telescope will be one of the most expensive things NASA has ever built. Its segmented mirror is so big that, once it's in space, it will have to unfold like an elaborate piece of origami. And to make observations, it will need to be a million miles from Earth, so far that no astronauts could fix it if it breaks.
But the Webb will be able to do things no other telescope can. It is designed to capture light from the first stars and galaxies, which has been traveling billions of years across the universe to reach our solar system. It will probe the atmospheres of potentially habitable planets outside the solar system. Astronomer John Mather is the telescope's project scientist at NASA, and he is pretty sure it's going to do other things too:
"Every time we build bigger or better pieces of equipment, we find something astonishing," he says.
The Webb is currently scheduled for launch in 2018.
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The ambitious telescope is the largest ever launched into space. It is set to launch in 2018.
Chris Gunn/NASA
Quelle: npr
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Update: 30.01.2016
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NASA Webb Telescope mirrors installed with robotic arm precision
Inside a massive clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland the James Webb Space Telescope team is steadily installing the largest space telescope mirror ever. Unlike other space telescope mirrors, this one must be pieced together from segments using a high-precision robotic arm.
The team uses a robotic arm called the Primary Mirror Alignment and Integration Fixture to lift and lower each of Webb's 18 primary flight mirror segments to their locations on the telescope structure. Each of the mirrors is made with beryllium, chosen for its properties to withstand the super cold temperatures of space. Each segment also has a thin gold coating to reflect infrared light. These mirror segments will function as one when the telescope is in orbit.
"In order for the combination of mirror segments to function as a single mirror they must be placed within a few millimeters of one another, to fraction-of-a-millimeter accuracy. A human operator cannot place the mirrors that accurately, so we developed a robotic system to do the assembly," said NASA's James Webb Space Telescope Program Director Eric Smith, at Headquarters in Washington.
To precisely install the segments, the robotic arm can move in six directions to maneuver over the telescope structure. While one team of engineers maneuvers the robotic arm, another team of engineers simultaneously takes measurements with lasers to ensure each mirror segment is placed, bolted and glued perfectly before moving to the next.
"While the team is installing the mirrors there are references on the structure and the mirrors that allow the team to understand where the final mirror surface is located," said Harris Corporation's James Webb Space Telescope's Assembly Integration and Test Director Gary Matthews Greenbelt, Maryland.
The team uses reference points on the telescope structure called Spherically Mounted Retroreflectors to accomplish this feat. A laser tracker, similar to the ones used by surveyors, looks at those reference points and can determine where the mirror segments go.
"Instead of using a measuring tape, a laser is used to measure distance very precisely," said Matthews. "Based off of those measurements a coordinate system is used to place each of the primary mirror segments. The engineers can move the mirror into its precise location on the telescope structure to within the thickness of a piece of paper."
Harris Corporation engineers are helping build NASA's ultra-powerful James Webb Space Telescope. Harris is responsible for integrating components made by various members of the team to form the optical telescope element, which is the portion of the telescope that will collect light and provide sharp images of deep space.
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A robotic arm called the Primary Mirror Alignment and Integration Fixture is used to lift and lower each of Webb's 18 primary flight mirror segments to their locations on the telescope structure. Image courtesy NASA/Chris Gunn.
Quelle: SD
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Update: 4.02.2016
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NASA's James Webb Space Telescope Primary Mirror Fully Assembled

nside a massive clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland the James Webb Space Telescope team used a robotic am to install the last of the telescope's 18 mirrors onto the telescope structure.
The 18th and final primary mirror segment is installed on what will be the biggest and most powerful space telescope ever launched. The final mirror installation Wednesday at NASA’s Goddard Space Flight Center in Greenbelt, Maryland marks an important milestone in the assembly of the agency’s James Webb Space Telescope.
“Scientists and engineers have been working tirelessly to install these incredible, nearly perfect mirrors that will focus light from previously hidden realms of planetary atmospheres, star forming regions and the very beginnings of the Universe,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “With the mirrors finally complete, we are one step closer to the audacious observations that will unravel the mysteries of the Universe.”
Using a robotic arm reminiscent of a claw machine, the team meticulously installed all of Webb's primary mirror segments onto the telescope structure. Each of the hexagonal-shaped mirror segments measures just over 4.2 feet (1.3 meters) across -- about the size of a coffee table -- and weighs approximately 88 pounds (40 kilograms). Once in space and fully deployed, the 18 primary mirror segments will work together as one large 21.3-foot diameter (6.5-meter) mirror.
"Completing the assembly of the primary mirror is a very significant milestone and the culmination of over a decade of design, manufacturing, testing and now assembly of the primary mirror system," said Lee Feinberg, optical telescope element manager at Goddard. "There is a huge team across the country who contributed to this achievement."
While the primary mirror installation may be finished on the tennis court-sized infrared observatory, there still is much work to be done.
"Now that the mirror is complete, we look forward to installing the other optics and conducting tests on all the components to make sure the telescope can withstand a rocket launch," said Bill Ochs, James Webb Space Telescope project manager. "This is a great way to start 2016!"
The mirrors were built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and optical system design. The installation of the mirrors onto the telescope structure is performed by Harris Corporation, a subcontractor to Northrop Grumman. Harris Corporation leads integration and testing for the telescope.
“The Harris team will be installing the aft optics assembly and the secondary mirror in order to finish the actual telescope,” said Gary Matthews, director of Universe Exploration at Harris Corporation. “The heart of the telescope, the Integrated Science Instrument Module, will then be integrated into the telescope. After acoustic, vibration, and other tests at Goddard, we will ship the system down to Johnson Space Center in Houston for an intensive cryogenic optical test to ensure everything is working properly.”
The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb will study many phases in the history of our universe, including the formation of solar systems capable of supporting life on planets similar to Earth, as well as the evolution of our own solar system. It’s targeted to launch from French Guiana aboard an Ariane 5 rocket in 2018. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Quelle: NASA
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Update: 24.02.2016
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NASA's James Webb Space Telescope Coming Together Over Next Two Years
The year 2015 marked big progress on NASA's James Webb Space Telescope and there are still a number of large milestones before the next generation telescope is launched in 2018. Recently, all of the 18 segments of the Webb telescope primary mirror segments were installed on the observatory's backplane at NASA's Goddard Space Flight Center in Greenbelt, Maryland. But that's just one component of the Webb. 
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Completing the assembly of the primary mirror, which took place at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is a significant milestone and the culmination of over a decade of design, manufacturing, and testing the agency’s James Webb Space Telescope.
Credits: Credit: NASA
Over the next two years, more components of the Webb will be integrated onto the spacecraft and it will visit three more locations before launch.
"From 2016 to 2018, there are installations and tests for the telescope and the telescope plus the instruments, followed by shipping to NASA's Johnson Space Center in Houston, Texas where end-to-end optical testing in a simulated cryo-temperature and vacuum space environment will occur," said Paul Geithner, Webb telescope manager - Technical, at NASA Goddard. “Then all the parts will be shipped to Northrop Grumman for final assembly and testing, then to French Guiana for launch.”
Here is a general list of milestones before launch:
At NASA Goddard:
Aft-Optics System installation
Secondary mirror installation
Integrated Science Instrument Module (ISIM) Installation into Telescope Structure
Metrology test of Telescope and Instruments
Vibration test of Telescope and Instruments
Acoustic test of Telescope and Instruments
At NASA Johnson Space Center:
Optical test of Telescope and Instruments in Chamber A
At Northrop Grumman:
Assemble Spacecraft Element
Finish Sunshield and Integrate into Spacecraft
Assembling entire Observatory (Telescope and Instruments and Spacecraft)
Observatory-level tests
Transport to French Guiana
The two largest parts of the observatory are the primary mirror and the tennis-court-sized sunshield. Additionally, there are four scientific instruments—cameras and spectrographs with detectors able to record extremely faint signals—that will fly aboard Webb.  All four flight science instruments were integrated into the Integrated Science Instrument Module (ISIM) in March 2014 and since have been undergoing multiple tests. However, the ISIM has not yet been added to the observatory. 
Over the next year, teams at Goddard will work to complete the telescope by installing the other optics in addition to the primary mirror segments. The other optics include installing the aft-optics subsystem or AOS, secondary mirror and both fixed and deployed radiators. Once complete, engineers will connect the Telescope and instruments together when the ISIM is attached to the observatory.   
Testing is a continuous part of the assembly process. "After the mating of the ISIM, to the Telescope there will be a room-temperature optical check before a simulated launch environment exposure," Geithner said. That means the observatory will undergo vibration and acoustic testing to ensure it can endure the sound and shaking that occurs during launch. After those tests, there is yet another room-temperature optical check.
Once all of those milestones are accomplished, the observatory will then be prepared and flown to NASA's Johnson Space Center, Houston, Texas.
Once at Johnson, the observatory will endure end-to-end optical testing in a simulated
cryo-temperature and vacuum space environment in Chamber-A. Chamber-A is NASA's giant thermal vacuum chamber where the Webb telescope pathfinder or non-flight replica was tested in April 2015.
After NASA Johnson the Webb telescope will be then transported to Northrop Grumman in Redondo Beach, California where engineers will connect the telescope and instruments together with the spacecraft and sunshield to form the complete Observatory. Once every component is together, more testing is done. That testing is called "Observatory-level testing." It's the last exposure to a simulated launch environment before flight and deployment testing on the whole observatory.
What follows the flight and deployment testing is the shipping of the complete observatory to the launch site in South America where the Webb telescope is slated to launch in 2018.
The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, the European Space Agency and the Canadian Space Agency.
Quelle: NASA
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Update: 8.03.2016
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NASA's James Webb Space Telescope Secondary Mirror Installed

The sole secondary mirror that will fly aboard NASA's James Webb Space Telescope was installed onto the telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland, on March 3, 2016.
The Webb telescope uses many mirrors to direct incoming light into the telescope's instruments. The secondary mirror is called the secondary mirror because it is the second surface the light from the cosmos hits on its route into the telescope.
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In this photo, engineers are seen installing the secondary mirror onto the telescope.
Credits: NASA/Chris Gunn
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Before its launch, engineers must build and test the telescope rigorously to ensure it survives its launch and its trip one million miles out into space. The James Webb Space Telescope is too large to fit into a rocket in its final shape so engineers have designed it to unfold like origami after its launch.
That unfolding, or deployment, includes the mirrors on the observatory, too.
The secondary mirror is supported by three struts that extend out from the large primary mirror. The struts are almost 25 feet long, yet are very strong and light-weight. They are hollow composite tubes, and the material is about 40-thousandths of an inch (about 1 millimeter) thick. They are built to withstand the temperature extremes of space.
Unlike the 18 primary segments that make up the biggest mirror on the Webb telescope, the secondary mirror is perfectly rounded. The mirror is also convex, so the reflective surface bulges toward a light source. It looks much like the curved mirrors on the walls near parking garage exits that let motorists see around corners. The quality of the secondary mirror surface is so good that the final surface at cold temperatures does not deviate from the design by more than a few millionths of a millimeter - or about one ten-thousandth the diameter of a human hair.
The powerful primary mirror of the Webb telescope is designed to gather the faint light from the first and most distant galaxies. The Webb telescope has 21 mirrors, 18 of which are primary mirror segments working together as one large 21.3-foot (6.5-meter) primary mirror. The primary mirror was completed when the 18th and final segment was installed on Feb. 4, 2016 at NASA Goddard.
The secondary mirror and all of the mirror segments are made of beryllium, which was selected for its stiffness, light weight and stability at cryogenic temperatures. Bare beryllium is not very reflective of near-infrared light, so each mirror is coated with about 0.12 ounces of gold to enable it to efficiently reflect infrared light (which is what the Webb telescope's cameras see).
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The mirrors were built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and optical system design. The installation of the mirrors onto the telescope structure is performed by Harris Corporation, a subcontractor to Northrop Grumman. Harris Corporation leads integration and testing for the telescope.
The most powerful space telescope ever built, the Webb telescope will provide images of the first galaxies ever formed and study planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
Quelle: NASA
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Update: 21.03.2016
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NASA Marks Major Milestones for the James Webb Space Telescope

NASA's James Webb Space Telescope just got a little closer to launch with the completion of cryogenic testing on its science cameras and spectrographs and the installation of the final flight mirrors.

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NASA's James Webb Space Telescope completed primary mirror sits in the cleanroom at NASA Goddard Space Flight Center, and supported over it on the tripod is the secondary mirror.
Credits: NASA/Chris Gunn
After over a year of planning, nearly four months of final cryo (cold) testing and monitoring, the testing on the science instruments module of the observatory was completed. They were removed from a giant thermal vacuum chamber at NASA's Goddard Space Flight Center in Greenbelt, Maryland called the Space Environment Simulator, or SES, that duplicates the vacuum and extreme temperatures of space. The SES is a 40-foot-tall, 27-foot-diameter cylindrical chamber that eliminates almost all of the air with vacuum pumps and uses liquid nitrogen and even colder gaseous helium to drop the temperature.
"We needed to test these instruments against the cold because one of the more difficult things on this project is that we are operating at very cold temperatures," said Begoña Vila, NASA's Cryogenic Test Lead for the ISIM at NASA Goddard. The ISIM, or Integrated Science Instrument Module is one of three major elements that comprise the James Webb Space Telescope Observatory flight system. "We needed to make sure everything moves and behaves the way we expect them to in space. Everything has to be very precisely aligned for the cameras to take their measurements at those cold temperatures which they are optimized for."
The testing is critical because at these instrument’s final destination in space, one million miles away from Earth, it will operate at incredibly cold temperatures of minus 387 degrees Fahrenheit, or 40 degrees Kelvin. This is 260 degrees Fahrenheit colder than any place on the Earth’s surface has ever been.
"This is the culmination of a lot of hard work by a lot of people who have been working for many, many years," said Jamie Dunn, NASA's Integrated Science Instrument Module Manager for the Webb telescope at Goddard. "This final test was phenomenal, everything is working spectacularly well.
The science instrument modules tested consist of the mid-infrared instrument (MIRI), jointly developed by a nationally funded European Consortium under the auspices of the European Space Agency (ESA) and the Jet Propulsion Laboratory; a near infrared spectrometer (NIRSpec), jointly developed by Airbus for ESA and the U.S.; the Fine Guidance Sensor/ Near-InfraRed Imager and Slitless Spectrograph, provided by the the Canadian Space Agency and developed by COM DEV International, Cambridge, Ontario, Canada; and Near Infrared Camera (NIRCam), built by a team at the University of Arizona and Lockheed Martin's Advanced Technology Center.
On March 6, 2016, shortly after the successful instrument testing, the last mirrors in Webb’s optical path were installed into the telescope. Now the telescope is officially optically complete.  
"Optical completeness means that all of the telescope mirrors have been installed," said Lee Feinberg, the Webb telescope Optical Telescope Element Manager, at Goddard. "We can now say ‘we have a telescope’—it’s a huge milestone many years in the making."
Once launched into space, this telescope will capture faint light from the very first objects that illuminated the universe after the Big Bang. To make observations of galaxies and stars from that far away, the telescope has a unique set of mirrors: a 25 square meter (~269 square feet) primary mirror consisting of 18 hexagonal concave segments, a secondary rounded, convex mirror, a tertiary concave mirror, and a moveable turning flat mirror called the fine steering mirror.
The Webb telescope’s primary mirror segments and secondary mirror are made of beryllium, which was selected for its stiffness, light weight and stability at cryogenic temperatures. Bare beryllium is not very reflective of near-infrared light, so each mirror is coated with about 0.12 ounces of gold to enable it to efficiently reflect infrared light (which is what the Webb telescope's cameras see).
The anchor of the optical system is the last (third) set of mirrors—the tertiary mirror and the fine steering mirror. These two mirrors are located inside the Aft Optics Subsystem (AOS), which is a phone booth-sized beryllium structure surrounded in black covering.  It is located right in the center of the primary mirror, and about half of it sticks up above the primary mirror.
After incoming light hits the expansive primary mirror, it is directed onto the small circular secondary mirror, which reflects it back in the direction of the primary mirror and into the AOS. [Animation: https://youtu.be/y9Z2GbFJWmo ] Inside the back end of the AOS is the tertiary mirror, where light bounces forward to the fine steering mirror at the ‘front’ of the AOS, which then reflects it out the back of the AOS to a focus behind the primary mirror for the scientific instruments. 
"The completion of these major milestones represent huge achievements for NASA and our industry, European, Canadian, and academic partners.  ISIM and the telescope only reached these milestones because of the passion, dedication, and imagination of an outstanding group of individuals. The next major step is assembling the instrument module and the telescope together to complete the entire ‘cold’ section of the Webb observatory," said Bill Ochs, Webb telescope Project Manager at Goddard.
The mirrors were built by Ball Aerospace & Technologies Corporation, in Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and optical system design. The installation of the mirrors onto the telescope structure is performed by Harris Corporation, a subcontractor to Northrop Grumman. Harris Corporation leads integration and testing for the telescope.
The most powerful space telescope ever built, the Webb telescope will provide images of the first galaxies ever formed and study planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
Quelle: NASA
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Update: 30.03.2016
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James Webb Space Telescope's Instruments Removed From Super-Cold Chamber

This rare overhead view of the thermal vacuum chamber at NASA's Goddard Space Flight Center in Greenbelt, Maryland, shows the Integrated Science Instrument Module (ISIM) when it was lowered into the chamber to begin its final cryogenic test at Goddard. The test was recently completed successfully.
Credits: NASA/Chris Gunn
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A new video from NASA shows the James Webb Space Telescope's cameras and spectrographs being lifted out of the Space Environment Simulator at NASA's Goddard Space Flight Center in Greenbelt, Maryland. These vital parts of the telescope endured their last super-cold test here.
The Integrated Science Instrument Module, or ISIM, holds all of the Webb telescope’s cameras and spectrographs. The module is wrapped in special blanketing to keep everything spotlessly clean.
For months, these components were tested inside the Space Environment Simulator. This simulator is a cylindrical chamber 40 feet tall and 27 feet wide. Vacuum pumps eliminate the air within; and liquid nitrogen and even colder gaseous helium drop the temperature to simulate the conditions in space where the Webb telescope will orbit. The testing is critical because these instruments must operate at incredibly cold temperatures around minus 387 F, or 40 kelvins. This is 260 F colder than any temperature ever recorded on Earth’s surface.
After the test the components were moved inside Goddard's massive clean room. The instruments will next be integrated onto the observatory to join the telescope's mirrors.
The science instrument modules tested consist of the mid-infrared instrument (MIRI), jointly developed by a nationally funded European Consortium under the auspices of ESA (the European Space Agency) and NASA's Jet Propulsion Laboratory in Pasadena, California; a near infrared spectrometer (NIRSpec), jointly developed by Airbus for ESA and the U.S.; the Fine Guidance Sensor and Near-InfraRed Imager and Slitless Spectrograph, provided by the Canadian Space Agency and developed by COM DEV International, Cambridge, Ontario, Canada; and Near Infrared Camera (NIRCam), built by a team at the University of Arizona and Lockheed Martin's Advanced Technology Center.
The James Webb Space Telescope is the scientific successor to NASA's Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb will study many phases in the history of our universe, including the formation of solar systems capable of supporting life on planets similar to Earth, as well as the evolution of our own solar system. It’s targeted to launch from French Guiana aboard an Ariane 5 rocket in 2018. Webb is an international project led by NASA with its partners, ESA and the Canadian Space Agency.
Quelle: NASA
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