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James Webb Space Telescope successfully deploys its huge sunshield

The James Webb Space Telescope has successfully unfurled its massive sunshield, marking the completion of a major step in its deployment as the observatory moves toward full operations.

The most powerful space telescope ever built launched atop an Ariane 5 rocket on December 25. At the time of writing, Webb has traveled 575,000 miles and is 65% of the distance to its destination orbit, which it’s expected to reach toward the end of this month.

News of the sunshield’s successful deployment was shared by NASA early evening Pacific time on Tuesday, January 4. The crucial maneuver to unfurl the 47-foot-wide shield took several days to complete, with the last step involving a tensioning process that stretched each of its five layers into their final position.

If anything had gone wrong with the sunshield’s deployment, it could have signaled the end of a $10 billion mission that’s been decades in the making.

The next big moment involves the opening up of the all-important primary mirror that will enable the observatory to peer into space so it can hopefully uncover some of the secrets of the universe during Webb’s multiyear mission.

The deployment process of the 18-segment, 21-foot-wide primary mirror will begin later this week, once the setup of the smaller secondary mirror has been confirmed.

The primary mirror deployment involves the locking into place of two sets of mirror segments around the main section.

A diagram of the James Webb Space Telescope.
A diagram showing the primary and secondary mirrors of the James Webb Space Telescope. NASA

The large size of both the primary mirror and the sunshield meant that the components had to be folded into a compact shape to fit inside the rocket fairing for launch.

It’s one of the most complicated space deployments ever attempted, though so far everything seems to be going to plan. Following the successful setup of the sunshield, the Webb team said that up to now “about 75%” of its 344 single-point failures have been handled without any issues.

Once the primary mirror is fully deployed, the Webb team will spend around five months aligning the telescope’s mirror and fine-tuning its onboard instruments.

Only then can the serious work of exploring deep space begin.

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Trevor Mogg
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