Sun protection is critical

Web telescope

The shield will be separated into five layers to protect the telescope from the Sun.

The next few days will be crucial to whether the new James Webb telescope is able to undertake its exciting mission to depict the first stars shining in the universe.

The space observatory, which was launched into orbit last Saturday, is trying to unpack its five-layer sunshade.

Without this barrier the size of a tennis court, Webb will not be able to achieve the super-cold temperatures required by its mirrors and instruments to function properly.

It’s a “make or break” moment for Webb.

Unfolding the shield’s membranes – each as thin as a human hair – will involve an astonishing symphony of hinges, motors, gears, springs, pulleys and cables.

There is very little room for error.

“The sunshade is like the parachute of a paratrooper,” said Krystal Puga of Northrop Grumman, the U.S. space company that assembled Webb.

The shield should unfold perfectly “without snags, without any tangles”.

The telescope – a joint project of the American, European and Canadian space organizations – enjoyed a spectacular launch from Earth on 25 December.

But it only marked the beginning of a six-month process of getting Webb ready to imagine the cosmos.

Because the observatory is so large, it had to be folded to fit into the nostril of its Ariane caster. And that means it now has to unfold into space before it can begin operations.

Mission controllers, based at the Space Telescope Science Institute (STScI) in Baltimore, Maryland, have already monitored the deployment of a solar panel, a communications antenna, and the expansion of a tower structure that holds Webbs’ mirrors.

But it was relatively straightforward activities compared to setup required for the shield that will protect the telescope from sunlight and heat.

Detailed implementation sequence

Detailed implementation sequence

Preparations for this rollout started well with the opening of the two pallet structures that hold the barrier membranes, made of an aluminum-coated polymer called kapton. These pallets folded outward in line on Tuesday and locked in place.

Now comes the difficult part: Pulling out the individual sheets of the shield, separating them into their five separate layers at clear intervals, and then tightening the entire system so that each membrane forms a smooth, rigid surface.

The difficulty is that the movement of the shield is inherently “floppy and indeterminate,” says Mike Menzel, NASA’s leading mission systems engineer on the Webb project.

“We can not really predict its shape, but we can limit it. We can try to prevent it from going places that we do not want it to go, places where it can hang or tear. And we do that by to build in restraint mechanisms. There are going to be many of these restraint mechanisms. “

Sun protection material

The screen material is made of kapton, which in everyday life is an electrical insulator

Webb will see the universe in infrared. It is at this longer wavelength of light that the faintest, most distant stars will be observed to shine.

But it is in the infrared that any hot object is also seen to glow – even the telescope itself, unless it is taken down to an ultra-low temperature.

Web mirrors and instruments are designed to operate below -230C. What’s more, the 6.5 m main mirror needs to be adjusted and focused at some point, and this requires one of the instruments, the Near-Infrared Camera (NIRCam), to be able to select a specimen that it wins. t be able to do if its detectors do not have the correct temperature. So the whole telescope system depends on the sun shield doing its job

If controllers on the STScI encounter difficulties over the next few days – for example, a pulley gets stuck – they have a number of pre-prepared strategies to work through the problems.

James Webb Space Telescope

James Webb Space Telescope

In extreme cases, it is even possible to give the entire telescope a little shake to release a reluctant mechanism.

But Nasa astrophysicist Amber Straughn told BBC News that tests performed before launch should lead to a positive result: “The whole implementation sequence – you might be thinking, ‘oh my gosh, it looks really hard’. And it’s true, it is “This is really, really hard technology. But you know, Nasa has never done without hard things, and so I have full confidence that it’s going to work.”

It would be Sunday at the earliest that the shield release can be completed.

Provided that the unfolding proceeds as it should, controllers will then proceed to the correct placement of Web’s mirrors.

A secondary reflecting surface must be extended on long booms, while the main mirror has “wings” that must rotate 90 degrees.

The telescope is currently on its way to an observation station 1.5 million km away on Earth’s night side. It was to arrive at the end of January.

It will then take another five months to get Webb ready to acquire his “first light” images. These will be revealed at a media conference, probably in June.

Web in clean room

Engineers have tested the implementation sequence over and over again

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