After today, the James Webb telescope will never see direct sunlight again

It’s time for the next – super exciting – step: unfolding the sun visor.

It’s been almost a week since took to the skies the most powerful observatory ever built. The James Webb telescope was origami folded to fit an Ariane-5 rocket. And now, as the telescope flies through the vast universe, are there more and more pieces taking place. Today the most difficult item is on the agenda: it’s time to deploy the solar shield.

To go out
In recent days, however, a few crosses have already been made. Yesterday, for example, James Webb already had his outstretched neck. This created an opening, so that enough space has now been created for the sunshade to fully extend. In addition, the covers that covered the folded sun visor were successfully removed yesterday.

It will also take some time before the sunshade is fully extended. This is because the shield still needs to be strained after being deployed. And it takes a little longer. The sun visor was probably fully prepared on Sunday.

sun visor
This means that part of James Webb will never see direct sunlight again. Because the sun visor divides Webb into a “warm side” and a “cold side”.

You are hot and you are cold …#NASAWebb is divided into “hot side” and “cold side” by its sun visor. The sun visor will always face the Sun to block heat and light, as Webb’s mirrors must remain extremely cold to observe weak heat signals in the universe! pic.twitter.com/GciNPo04nr

– NASA Webb Telescope (@NASAWebb) December 29, 2021

It’s really important. The James Webb telescope will primarily observe infrared light from faint, very distant objects. And to detect these weak signals, the telescope itself must be extremely cold. This is why a 5-layer sunshade, the size of a tennis court, was made. This shield will protect the telescope from light and external heat sources (such as the sun, earth, and moon) and heat radiated from the observatory itself. So you can compare this sunshade a bit to a parasol, which will always be facing the sun to repel heat and light.

The solar shield is tested on Earth.

5 layers
You might be wondering why the ingenious space telescope has a 5-layer lens hood instead of a thick one. This is because each successive layer of the solar shield is cooler than the layer below. The opening between the layers also provides an additional insulating effect. In short, a large, thick sunscreen conducts much more heat than a sunscreen made up of five layers separated by a vacuum.

Image: STScI

Equipment
The shiny silver material of the 5-layer sun visor is a complex and innovative piece of engineering. The lightweight shield is made of Kapton material, which has high heat resistance. Each layer is also coated with aluminum and has a specific thickness and size. The two warmer layers of the face facing the sun also have some sort of silicone coating to reflect the heat of the sun back into space. The kite-like shape and number of layers both play an important role. This way, each individual layer is positioned precisely so that the telescope can do its job as well as possible.

Teething has started. Because nothing should happen when deploying the sun visor. The lens hood is really crucial for the operation of the telescope. In any case, the team is well prepared. The steps have been extensively tested and practiced on earth. Still, it is exciting to know if the deployment of the solar shield in the universe, millions of kilometers from Earth and without the possibility of intervention, will also go as planned. To be continued…