{"id":10741,"date":"2021-12-28T23:14:55","date_gmt":"2021-12-28T15:14:55","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/high-stakes-sunshield-deployment-begins-on-webb-telescope\/"},"modified":"2021-12-28T23:14:55","modified_gmt":"2021-12-28T15:14:55","slug":"high-stakes-sunshield-deployment-begins-on-webb-telescope","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/high-stakes-sunshield-deployment-begins-on-webb-telescope\/","title":{"rendered":"High-stakes sunshield deployment begins on Webb telescope"},"content":{"rendered":"
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Artist\u2019s illustration of the Webb telescope\u2019s sunshield pallet opening. Credit: NASA<\/figcaption><\/figure>\n

Mission controllers started the risky process Tuesday to unfurl the James Webb Space Telescope\u2019s sunshield, a five-layer thermal barrier necessary to give the observatory infrared vision into the distant universe.<\/p>\n

Two large pallets containing the sunshield membranes were folded up on each side of Webb\u2019s primary mirror for launch. Now, with Webb on course toward an observing post nearly a million miles (1.5 million kilometers) from Earth, ground teams are ready to open up the sunshield to its full dimension.<\/p>\n

Made of five fragile kapton membranes, each as thin as a human hair, the sunshield will keep Webb\u2019s mirrors, instruments, and detectors in constant shadow, allowing their operating temperature to reach near minus 400 degrees Fahrenheit. Such cold conditions are required to allow Webb to see the faint infrared light from the first galaxies in the universe more than 13.5 billion light years away.<\/p>\n

Webb, the largest space telescope ever launched, had to fold up to fit inside the payload fairing of its Ariane 5 rocket for liftoff Christmas morning.<\/p>\n

\u201cWe built a world-class infrared telescope,\u201d said Mike Menzel, Webb\u2019s mission systems engineer at NASA\u2019s Goddard Space Flight Center. \u201cWe built it, we\u2019ve aligned it, we\u2019ve tested it, and proved it worked.\u201d<\/p>\n

\u201cNow, we\u2019re going to have to break it up, fold it up, and actually rebuild it on orbit \u2014 rebuild it, realign it, retune it and get it to work robotically on orbit. That\u2019s never been done before.\u201d<\/p>\n

Most NASA managers and astronomers waiting to use the nearly $10 billion Webb telescope give the same answer about the most stressful moment of the mission: Sunshield deployment.<\/p>\n

\u201cThe sunshield is one of these things that is almost inherently indeterministic,\u201d Menzel said. \u201cNASA is used to deploying rigid beams on hinges, because they\u2019re deterministic, you can determine how they move.\u201d<\/p>\n

Once the sunshield is opened to its full size \u2014 with the approximate dimensions of a tennis court \u2014 NASA will send commands to open wings on each side of the telescope\u2019s primary mirror, giving the aperture its final diameter of 21.3 feet (6.5 meters). A tripod-like structure with Webb\u2019s secondary mirror must also deploy.<\/p>\n

\u201cGiven that there are 40 different major deployments, and hundreds of pulleys and wires, the whole thing makes me nervous and will until its fully deployed,\u201d said John Grunsfeld, an astrophysicist, former astronaut, and head of NASA\u2019s science mission directorate from 2012 until 2016, a key period in Webb\u2019s development.<\/p>\n

But it\u2019s the sunshield that got the biggest share of Menzel\u2019s attention during the design and testing of Webb.<\/p>\n

Menzel compares predicting the behavior of the sunshield layers to guessing what a string will do when you push it on a table top.<\/p>\n

\u201cSo it is with the membranes of the sunshield,\u201d he said. \u201cSo we can\u2019t really predict their shape, but we can constrain it. \u201cWe can try to prevent it from going in places that we don\u2019t want it to go, places where it could snag or tear, or maybe impede the deployment of other members.\u201d<\/p>\n

If everything goes according to plan, the timeline to deploy and tension the sunshield will take five days. But mission planners have flexibility in that schedule, and could decide to postpone or defer some steps to look at data in the event of a problem.<\/p>\n

The first day of sunshield deployment apparently went off without a hitch. NASA said the two sunshield pallets lowered into position in front of and behind the telescope Tuesday. The two pallets extend 69.5 feet (21.2 meters) tip to tip.<\/p>\n

The pallets, called Unitized Pallet Structures, contain the five kapton sunshield layers carefully folded and stowed by engineers at Northrop Grumman, NASA\u2019s prime contractor for the Webb mission.<\/p>\n

\u201cWebb is beginning to resemble the form it will take when it is fully deployed \u2013 now that the mission operations team has successfully deployed and latched into place the observatory\u2019s forward and aft Unitized Pallet Structures,\u201d NASA said in an update late Tuesday.<\/p>\n

The forward pallet lowered first, with its unfolding finished at around 1:21 p.m. EST (1821 GMT) Tuesday, NASA said. The next step was the unfolding of the aft pallet, which was confirmed fixed in its deployed position at around 7:27 p.m. EST (0027 GMT).<\/p>\n

It took around 20 minutes to deploy the forward pallet, and 18 minutes to move the aft pallet, NASA said. But the process included additional steps spanning several hours, allowing ground teams to monitor structural temperatures and maneuver the observatory with respect to the sun to provide optimal thermal conditions for the deployments, the agency said.<\/p>\n

Ground teams also turned on heaters, activated release mechanisms, and verified software configurations before latching the pallets into place, NASA said. Mission control for Webb is at the Space Telescope Science Institute in Baltimore, Maryland.<\/p>\n

\u201cEach deployment usually involves a bunch of motor checks, small moves to verify motor performance, heating of anything that is too cold, etc,\u201d said Keith Parrish, Webb\u2019s commissioning manager at NASA. \u201c<\/span>We also have to power on and configure our deployment electronics, which controls the whole show. \u201c<\/span><\/p>\n