The sun shield for the James Webb Space Telescope was put away seven months ago.
They had practiced putting it in soup to nuts. The cable ended up in the wrong place when they opened it. The second time, some of the glue they used to keep the cable in line caused a mechanical problem. The third attempt, after the techs cleaned the gunk, was seamless.
He said in an interview that none of the earlier problems were complete failures. The last time we unfolded it, we had no problems.
The observatory that was launched on Christmas will lead to many discoveries. The curtain of gas and dust that hides distant stars and other worlds will be pulled back with the help of technology. It will show the light from the billions of light-years away. Light waves are stretched into the IR by the expansion of space.
The sun shield has to be opened before the moon can be reached, so that the instruments can be protected from the sun's heat and light. The deployment is one of the most complicated and necessary for the mission. The task will take five days to complete.
The European Space Agency's science director described the process as a butterfly breaking through its pupa and unraveling its golden wings. Others called it risky.
The crew has built in backups and contingency plans to ensure that the $10 billion telescope works, said Jim Flynn, director of vehicle engineering for the lead industry partner on the project.
Flynn said that the system was designed so that if they see something they are not comfortable with, they can stop anywhere in the deployment.
Engineers and technicians are working on the deployment and tensioning of the five-layer sun shield system. Credit: NASA.
The telescope is shaded from the sun by the sun shield. The side facing the sun is 600 degrees cooler than the side facing the instruments. Without it, the heat coming off the sun, moon, Earth, and devices could blind the cameras. It needs to be extra cold to pick up faint heat signals from the far reaches of the universe.
The first thing to do is to unpack the two large pallets. The back of the plane seats have tray tables. The home of the telescope is pushed away from the spaceship, creating a gap for the sun shield to unfold and keeping the hot and cold ends separate.
There are 107 pins that secured the shield during the launch. They hold the folded material in place. It will take hours to remove the pins.
The delicate process of unfolding the material begins when the material is free. The booms slide out one side at a time. They pull the pleats as they move.
One of the biggest design challenges was figuring out how to keep the loose layers from billowing in an environment. An engineer on the team invented a system of magnets and straps to keep the folds together.
After the material is laid out, spreader bars rigged with cables and pulleys raise it up like a sail, one corner at a time. The sun shield layers are stretched as tight as possible.
NASA can't send out a rescue squad if something goes wrong. Engineers tried to make the system reliable by using highly durable parts. Not every part of the design could be duplicated. They have two different ways to control the pins, but they don't have two sets of pins.
Engineers built in extra deployment features if the sun shield gets stuck. Those are the names of the tools in the craft.
The ground crew could push or pull harder on devices to try to unstick them, like working on a jammed desk drawer. Imagine shaking that drawer to get rid of the stuff in it. The crew could initiate a low-level vibration by firing its rockets in different sequence.
If they want some parts to fly out, the "twirl" could be used. The entire observatory can be spun like a carousel. They could heat and cool it to loosen things up.
NASA doesn't think the sun shield will need these tricks to open. The agency says that the features are there for the unexpected, but that engineers have put more tests on the mission than any other.
We're having a bad day if we're doing twirls and shimmies.
About 20 to 25 engineers will be on stand-by in Redondo Beach, California, if needed. Flynn said that the models could be used for diagnosis. They can't send astronauts to look under the hood of the real thing.
A tech works on the sun shield for the James Webb Space Telescope. Credit: Northrop Grumman.
Flynn said the long time since the last opening doesn't make him stressed. It gives him confidence that it hasn't been handled too much and that it is vulnerable to human errors.
The worry for Parrish is whether the effort they put into packing it left it intact. He says that it's only as good as the last time you folded it.
As the deployment begins, Parrish won't be participating in any superstitions. Five days is too long for him.
He might whisper a few prayers.
He said that most of the people who worked on the project have lost friends. We'll look to the heavens and ask for help.
The telescope has a mirror- opening sequence.
