The primary mirror of the long-awaited James Webb Space Telescope (JWST) was opened for the last time on Earth before the launch of the observatory, currently scheduled for October 31, 2021.

During some of the final checkouts before the telescope heads to space, engineers commanded the 18 hexagonal mirrors to fully expand and lock into place, just like they will do once the Webb telescope reaches its destination in space.  

“Over the past few months, we have completed almost all of our deployments associated with post environmental testing,” said Bill Ochs, Project Manager for JWST at NASA, during a media briefing this week. “This includes things like mirror, the solar array, and as well as the very complex and challenging final successfully deployment of the sunshield, which is now folded back up and undergoing final stowing now.”

Ochs said the engineering and science teams have also completed the final ground segment tests where they actually commanded the observatory from the telescope’s Mission Operations Center at the Space Telescope Science Institute in Baltimore, Maryland.   

To deploy, operate and bring the golden mirrors into focus requires 132 individual actuators and motors in addition to complex backend software to support it. A proper deployment in space is critically important to allow the individual mirrors to work as one functional and massive reflector

The deployment on Earth, however, involves supporting the mirrored panels from a crane in a way that simulates the zero-gravity environment in space.

The process of deploying, moving, expanding and unfurling all of Webb’s many movable pieces after they have been exposed to a simulated launch is the best way to ensure they will perform as intended once in space. Credits: NASA/Chris Gunn

“We effectively have that mirror float like it does in space,” explained Northrop Grumman program manager Scott Willoughby. “We designed the mirror wings to operate in space, but we have to test them on the ground – and gravity can be pretty humbling.”

Once the wings are fully extended and in place, extremely precise actuators on the backside of the mirrors position and bend or flex each mirror into a specific “prescription.” Testing of each actuator and their expected movements was completed in a final functional test earlier this year.

“We are getting very close to shipping and launch,” said Greg Robinson, Program Director for JWST at NASA’s Science Mission
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