The James Webb telescope on a NASA image, before taking off to explore the far reaches of the Universe (NASA / Chris GUNN)
The James Webb Space Telescope on Tuesday took a major step towards the success of its mission with the full deployment of its heat shield, an essential element for conducting future observations of the cosmos.
Even if many operations still need to be successful for the observatory to be fully ready, the deployment of this sun visor was the “most difficult” on the list, Thomas Zurbuchen, head of scientific missions at NASA, recalled in a statement. , welcoming this success.
The shield is made of five layers each the size of a tennis court, intended to protect scientific instruments from the heat of our star. They have been carefully unfolded and stretched one by one since Monday.
Too large to fit into a rocket as it is, the telescope has indeed had to be folded on itself like an origami, and requires to be deployed in space during ultra-perilous procedures, which NASA normally avoids. .
“It’s a very special day,” tweeted astronomer Klaus Pontoppidan, chief scientist for James Webb. “I believe it is time to realize that we may soon have a fully operational giant space telescope.”
James Webb is awaited by astronomers around the world and must make it possible to observe in particular the first galaxies, formed just a few hundred million years after the Big Bang.
The most powerful space observatory ever designed, took off a little over a week ago from French Guiana and is currently more than 900,000 kilometers from Earth. It is still on its way to reach its final orbit, 1.5 million kilometers from us – four times the Earth-Moon distance.
In this place, in the event of a problem, no repair mission can be envisaged.
Its deployment, piloted from Baltimore, on the American east coast, must therefore be carried out without any missteps. More than a hundred engineers are currently working there 24 hours a day to ensure that everything is going as planned.
– Relief-
Nasa broadcast the event live on the internet on Tuesday morning. Since no aircraft on board can take photos of the observatory itself, the only images available were from the operations control room, where the deployment teams cheered with joy.
“The vibe was hard to describe. It was an amazing time. There was a lot of joy, a lot of relief,” Hillary Stock, sunshade deployment manager at Northrop Grumman, partner of The NASA.
“Everything went smoothly,” she added.
The shield measures approximately 20 by 14 meters and is designed in the shape of a diamond. Its layers, as thin as a hair, were previously folded like an accordion, and are now spaced a few tens of centimeters from each other.
They are made of kapton, a material chosen for its resistance to extreme temperatures: the face closest to the Sun can reach 125 ° C, and the furthest away -235 ° C.
Their deployment involved hundreds of pulleys and meters of cables to guide them, as well as motors to stretch each sail, from every corner of the diamond.
On Monday, the first three layers had been successfully unfolded and stretched. Tuesday morning, the teams did the same with the last two.
– Ready in 5 and a half months –
This heat shield is crucial because James Webb’s scientific instruments can only operate at very low temperatures and in darkness. The great novelty of this telescope is that it will indeed operate only in the near and middle infrared, wavelengths invisible to the naked eye.
However, to be able to detect the weak light coming from the far reaches of the Universe, it must in no case be disturbed by the radiations of the Sun, or those returned by the Earth and the Moon.
The next step is the deployment of the mirrors: first the secondary mirror, smaller and placed at the end of a tripod.
Then the iconic main mirror, covered in gold and measuring around 6.6 meters in diameter, whose two sides will open one after the other, which could be completed as early as Monday.
Once in its final configuration, James Webb will arrive at its destination, known as the Lagrange 2 point. The instruments will still need to cool and be calibrated, and the 18 hexagonal mirrors forming the main mirror will be very precisely adjusted.
Six months after takeoff, the telescope will then finally be ready to go back to the origins of the Universe, but also to search for habitable environments, outside our solar system.
la / iba