Webb Fully Unfurls for the Last Time on Earth. The Next Time Will Be in Space

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 Directorate. “Over the past year — this year of a pandemic — our employees have learned to live and work together like we’ve never imagined. But we kept everything moving … and now we are just doing all those ‘lasts’  — the last tests, last deployments we’ll ever do on Earth, the last stow.”

The plan is that JWST will be placed inside a large climate-controlled shipping container and taken on a ship from the Northrup Grumman facility where it is now, in California, to the European rocket facility at Kourou in French Guiana. The trip will take approximately two weeks and involve passage through the Panama Canal.

The Ariane5 lifting off from Kourou in French Guiana. Image: ESA/Arianespace.
The Ariane5 lifting off from Kourou in French Guiana. Image: ESA/Arianespace.

JWST will be launched aboard an Ariane 5 rocket.  However, the usually reliable Ariane 5 has seen problems on two previous launches with a “less than fully nominal separation of the fairing.” The rocket has been grounded for months to sort it out, and with two other launches on the manifest before JWST, this issue could potentially delay the launch of the high-profile space telescope in October, but perhaps only for a couple of weeks.

“They’re going through the process of getting the rocket ready for the upcoming launch, the first of the three,” Robinson said. “Once they launch, we’ll be able to launch in about four months after that.”

However, Robinson said on NASA’s and Northrup Grumman’s end, everything is going well, and they are not working any problems.

“Right now, we are not working any liens,” he said. “We are getting close to the goal line and just need to punch it over. We are in a really good place but have several reviews ahead of us to get to the next steps.”

Further reading/watching: NASA, Space News, Webb Media Day presentation