A massive backplane that will hold the primary mirror of NASA's James Webb Space Telescope
nearly motionless while it peers into space is another step closer to
completion for its launch date in 2018 with the recent assembly of the
support structure's wings that enable the mirror, made of 18 pieces of
beryllium, to fold up and fit inside a 16.4-foot (5-meter) fairing on a
rocket, and then unfold to 21 feet in diameter after the telescope is
delivered to space.
All that is left to build is the support fixture that will house an
integrated science instrument module, and technicians will connect the
wings and the backplane's center section to the rest of the observatory.
The center section was completed in April 2012 at ATK's Space Components facility in Magna, Utah. The JWT is the successor to NASA's Hubble Space Telescope.
It will be the most powerful space telescope ever built and observe the
most distant objects in the universe, provide images of the first
galaxies formed and see unexplored planets around distant stars.
Designed, built and set to be tested by ATK at its facilities in
Magna, Utah, the wing assemblies are extremely complex, with 900
separate parts made of lightweight graphite composite materials using
advanced fabrication techniques. ATK assembled the wing assemblies like a
puzzle with absolute precision. ATK and teammate Northrop Grumman of
Redondo Beach, Calif., completed the fabrication.
"We will measure the accuracy down to nanometers -- it will be an
incredible engineering and manufacturing challenge," said Bob Hellekson,
ATK's Webb Telescope program manager. "With all the new technologies
that have been developed during this program, the Webb telescope has
helped advance a whole new generation of highly skilled ATK engineers,
scientists and craftsmen while helping the team create a revolutionary
telescope."
When fully assembled, the primary mirror backplane support structure
will measure about 24 feet by 21 feet and weigh more than 2,000 pounds.
The backplane must be very stable, both structurally and thermally, so
it does not introduce changes in the primary mirror shape, and holds the
instruments in a precise position with respect to the telescope.
While the telescope is operating at a range of extremely cold
temperatures, from minus 406 to minus 360 degrees Fahrenheit, the
backplane must not vary more than 38 nanometers (about one
one-thousandth the diameter of a human hair). The thermal stability
requirements for the backplane are unprecedented.
"One of the test articles ATK built and tested is actually larger
than a wing," said Charlie Atkinson, deputy Webb Optical Telescope
Element manager for Northrop Grumman in Redondo Beach, Calif. "The
mirrors are attached to the wings, as well as the rest of the backplane
support structure, so the alignment is critical. If the wings distort,
then the mirror distorts, and the images formed by the telescope would
be distorted."
The Webb telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
Source: The Daily Galaxy via NASA
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