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James Webb’s sunshield extended to its full 47-foot width

Georgina Torbet
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Following a successful launch on Christmas day, the James Webb Space Telescope is currently heading through space, having traveled almost 500,000 miles from Earth. It is just over halfway to its eventual destination: The L2 orbit, called a Lagrange point, where it will move around the sun in a complex path. As James Webb travels it is slowly unfolding its various hardware which had to be folded up origami-style to fit into the Ariane 5 rocket which launched it.

The telescope is currently in the process of deploying its tennis court-sized sunshield — a complex operation of many steps which began earlier this week and is expected to take four to five days. This started with the deployment of structures called Pallet Structures, which hold the sunshield itself plus components like cables and pulleys. With the forward and aft pallet structures in place, the next step was deploying the Deployable Tower Assembly, a structure that creates space between the spacecraft and the telescope to make space for the sunshield. This deployment took place on Wednesday, December 29.

With that done, over Thursday and Friday this week the team deployment the aft moment flap to help maintain the telescope’s orientation once it is in orbit, and released the sunshield covers which protected the thin sunshield during launch.

The latest update from NASA is that James Webb has extended its two sunshield mid-booms. These “arms” extend to the left and right of the telescope, pulling the thin membrane of the sunshield with them until it spanned the full 47 feet of its width. Their deployment means that all of the 107 release devices for the various parts of the sunshield deployment have now been released.

“The mid-booms are the sunshield’s workhorse and do the heavy lifting to unfold and pull the membranes into that now-iconic shape,” said Keith Parrish, Webb observatory manager at NASA’s Goddard Space Flight Center, in a blog post.

The deployment of the mid-booms took a little longer than expected as the team paused to assess a possible issue with the rolling up of the sunshield cover. The switches on the cover seemed not to have activated, but other sensors showed that the cover had indeed rolled up correctly. They decided to go ahead and the deployment was successful.

“Today is an example of why we continue to say that we don’t think our deployment schedule might change, but that we expect it to change,” Parrish said. “The team did what we had rehearsed for this kind of situation — stop, assess, and move forward methodically with a plan. We still have a long way to go with this whole deployment process.”

The next step is for the sunshield to be tensioned, in which each of its five layers will be stretched into place, which is expected to happen over the next few days.

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