After takeoff, Webb traveled for about three days until it started unfurling its sunshield. It took eight days in total for the thing to finally deploy. And if you're wondering why that's because the process involves pulling out a set of five layers that must get individually stretched tight or tensioned.
Each one of these layers is made of plastic, and it's just as thin as human hair. The sheets are all coated with a reflective metal that helps protect the telescope from the Sun's heat and light. They actually are capable of reducing solar energy exposure from over 200 kilowatts to only a fraction of a watt. This is all necessary in order for Webb's scientific instruments to function properly.
"Unfolding Webb's sunshield in space is an incredible milestone, crucial to the success of the mission," said Gregory L. Robinson, Webb's program director at NASA Headquarters.
Now that the sunshield has been finally deployed, the telescope still has some more tasks to do in the following five and a half months, which are focused on its setup. Next, the observatory will open up its 21 ft (6.5-meter) golden mirror, calibrate the science instruments, and ensure that the optics inside are properly aligned.
Once that's out of the way for Webb, it will be ready to start spying on distant galaxies and return incredible images that will help scientists understand the origins of the universe and how everything around formed.
This is it: we’ve just wrapped up one of the most challenging steps of our journey to #UnfoldTheUniverse.— NASA Webb Telescope (@NASAWebb) January 4, 2022
With all five layers of sunshield tensioning complete, about 75% of our 344 single-point failures have been retired! pic.twitter.com/P9jJhu7bJX