James Webb Space Telescope "Pathfinder" Backplane in the Cleanroom

The center section of the "pathfinder" (test) backplane of NASA's James Webb Space Telescope (JWST) arrived at the Goddard Space Flight Center in July 2014, to be part of a simulation of putting together vital parts of the telescope.

In this photograph, the backplane is hoisted into place in the assembly stand in NASA Goddard's giant cleanroom, where over the next several months engineers and scientists will install two spare primary mirror segments and a spare secondary mirror.

By installing the mirrors on the replica, technicians are able to practice this delicate procedure for when the actual flight backplane arrives.

Installation of the mirrors on the backplane requires precision, so practice is important.


This is a time-lapse video of the center section of the 'pathfinder' backplane for NASA's James Webb Space Telescope being moved into the clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland. TRT: 1:27 

Credit: NASA/Chris Gunn

NASA James Webb Space Telescope: backplane arrives at Marshall Centre for testing

The James Webb Space Telescope's backplane element arrives at the Marshall Center. 

Credit: NASA/MSFC/Fred Deaton

A major piece of the James Webb Space Telescope, the mirror's primary backplane support, arrived Aug. 22 at NASA's Marshall Space Flight Center in Huntsville, Ala., for testing in the X-ray and Cryogenic Test Facility.

The backplane is the backbone of the telescope, supporting its 18 beryllium mirrors, instruments and other elements while the telescope is looking into deep space.

The Webb Telescope is the world's next-generation space observatory and successor to the Hubble Space Telescope.

To prepare the telescope for the extreme temperatures of space, engineers at the facility have carefully examined the telescope's mirrors inside a vacuum chamber that simulates the hypercold of space, chilling the hardware from room temperature down to a frigid minus 414 degrees Fahrenheit.

The backplane is the latest and final piece of the telescope to undergo this extreme conditioning at the Marshall Center.

The X-ray and Cryogenic Facility at the Marshall Center (PDF) is the world's largest X-ray telescope test facility and offers a unique, cryogenic, clean-room optical test environment.

Cryogenic testing will take place in a 7,600-cubic-foot, helium-cooled vacuum chamber, chilling the Webb support structure from room temperature to simulate the frigid atmosphere of space.

While the structure changes temperature, test engineers will precisely measure its structural stability to ensure it will perform as designed in the extreme temperatures of space.

The cryogenic testing is targeted to begin in September.

"This testing of the backplane will verify limited movement of the structure when exposed to cryogenic temperatures," said Helen Cole, project manager for Webb Telescope mirror activities at the test facility.

"This is important to overall performance of the telescope."

Crews unload the James Webb Space Telescope's "backplane," which was flown aboard a Lockheed C-5 airplane to NASA’s Marshall Space Flight Center in Huntsville, Ala. 

Credit: NASA/MSFC/Fred Deaton

"Ensuring the best performance for the telescope requires evaluating the hardware at temperatures just as cold as in the environs of space," said Jeff Kegley, the test facility's manager.

 "This is the last in a series of Webb Telescope tests our facility has been performing since 2008; it's great to have the hardware here."

A joint project of NASA, the European Space Agency and the Canadian Space Agency, the Webb Telescope will observe the most distant objects in the universe, provide images of the first galaxies formed and see unexplored planets around distant stars.

ATK built the backplane structure at its facility in Magna, Utah, under a contract with prime contractor Northrop Grumman.

James Webb Space Telescope: The center section of the Primary Mirror Backplane Support Structure

The center section of the James Webb Space Telescope flight backplane, or Primary Mirror Backplane Support Structure, at ATK’s manufacturing facility in Magna, Utah. 

Credit: ATK

Assembly of the backbone of NASA's James Webb Space Telescope, the primary mirror backplane support structure, is a step closer to completion with the recent addition of the backplane support frame, a fixture that will be used to connect all the pieces of the telescope together.

The backplane support frame will bring together Webb's center section and wings, secondary mirror support structure, aft optics system and integrated science instrument module.

The backplane support frame also will keep the light path aligned inside the telescope during science observations.

Measuring 11.5 feet by 9.1 feet by 23.6 feet and weighing 1,102 pounds, it is the final segment needed to complete the primary mirror backplane support structure.

This structure will support the observatory's weight during its launch from Earth and hold its18-piece, 21-foot-diameter primary mirror nearly motionless while Webb peers into deep space.

ATK has begun final integration of the backplane support frame to the backplane center section, which it completed in April 2012 and two backplane wing assemblies, which it completed in March.

"Fabricating and assembling the backplane support frame of this size and stability is a significant technological step as it is one of the largest cryogenic composite structures ever built," said Lee Feinberg, James Webb Space Telescope optical telescope element manager at NASA's Goddard Space Flight Center in Greenbelt, Md.

The frame, which was built at room temperature but must operate at temperatures ranging from minus 406 degrees to minus 343 degrees Fahrenheit, will undergo extremely cold, or cryogenic, thermal testing at NASA's Marshall Space Flight Center in Huntsville, Ala.

The backplane support frame and primary mirror backplane support structure will shrink as they cool down in space.

This x-ray diagram of NASA’s James Webb Space Telescope shows where the backplane support frame (BSF) is in relation to the whole observatory. 

The BSF is the backbone of the observatory, is the primary load carrying structure for launch, and holds the science instruments. 

Photo Credit: Northrop Grumman

The tests, exceeding the low temperatures the telescope's backbone will experience in space, are to verify the components will be the right size and operate correctly in space.

The primary mirror backplane support structure consists of more than 10,000 parts, all designed, engineered and built by ATK.

The support structure will measure about 24 feet tall, 19.5 feet wide and more than 11 feet deep when fully deployed, but weigh only 2,138 pounds with the wing assemblies, center section and backplane support frame attached.

When the mission payload and instruments are installed, the fully populated support structure will support more than 7,300 pounds, more than three times its own weight.

Artist's concept of the James Webb Space Telescope in orbit. Credit: NASA

The primary mirror backplane support structure also will meet unprecedented thermal stability requirements to minimize heat distortion.

While the telescope is operating at a range of extremely cold temperatures, from minus 406 degrees to minus 343 degrees Fahrenheit, the backplane must not vary more than 38 nanometers (approximately 1 one-thousandth the diameter of a human hair).

The primary backplane support structure is made of lightweight graphite materials using and advanced fabrication techniques.

The composite parts are connected with precision metallic fittings made of invar and titanium.