Designed and fabricated by Alliant Techsystems for Northrop Grumman, the JWST prime contractor, the BSTA is a full-scale sub-section of the mirror's backplane, a structure that holds and supports the observatory's sensitive, lightweight mirrors and mirror controls.

The test article holds up to three of JWST's 18 primary mirror segments.

The BSTA testing sequence is designed to verify that the backplane has achieved Technology Readiness Level 6, Northrop Grumman said in a news release. TRL is a measure used by NASA and other government agencies to assess the maturity of evolving technologies before they are incorporated into operational systems.

Achieving TRL 6 means a prototype has been successfully tested in a simulated space environment and is ready to move into the final design phase.

"Our challenge was to design and fabricate a structure that is very lightweight yet strong and stable at temperatures as low as -405 degrees Fahrenheit," said Bob Hellekson, ATK's JWST program manager.

"We're pushing the state-of-the-art in this structure. This design had to ensure that any nominal temperature changes would not affect the ability of the mirrors to capture a clear image."

Tests on the BSTA are designed to measure stability at cryogenic temperatures as low as 30 degrees Kelvin (-405 degrees F) for a period of two to three days.

Slated for completion in late fall, testing is being conducted at Marshall in an X-ray cryogenic facility with a specially modified vacuum chamber.

"Our teammates at ATK have done an exceptional job designing an assembly that is critical to the telescope's ability to focus accurately," said Martin Mohan, Northrop Grumman's JWST program manager. "The testing at Marshall will demonstrate the high level of backplane maturity."

The NASA-supplied instrumentation used in the tests, a speckle interferometer, is also a step forward in technological capability. The device uses the diffusely scattered light that reflects off the BSTA surface to measure accurately minute variations in the mirror mount locations.

The tests are especially rigorous because the BSTA must perform to tolerances measured in nanometers - about four atoms wide.

BSTA is one of three technology demonstration tests on the observatory's optical telescope element that the Northrop Grumman-led team is planning for JWST this year.

The other tests are:

- Primary mirror segment. This test will measure how well a primary mirror segment assembly survives in a simulated launch environment. A flight mirror segment will undergo vibro-acoustic tests at Ball Aerospace this summer, and engineers will measure how well the mirror and its actuator system stand up to the simulated shaking and sound they will encounter during launch.

- Wavefront sensing and control. Algorithms and actuators comprising the wave front sensing and control system's ability to align and adjust the mirrors will be tested on a one-sixth scale testbed telescope. The tests will be completed in late fall at Ball Aerospace.

Northrop Grumman Corporation leads the JWST observatory and overall system design and development effort under contract to NASA's Goddard Space Flight Center.

James Webb Space Telescope will explore all fields of astronomy and every phase of history, from the first luminous glows after the Big Bang to the formation of star systems capable of supporting life on planets like Earth to the evolution of our own solar system.

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