On Tuesday, January 4, the James-Webb space telescope took a major step towards the success of its mission, with the full deployment of its heat shield. An essential element for carrying out future observations of the cosmos.
This sun visor is made up 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, the telescope must have been folded over on itself like an origami and requires deployment into space. A very perilous procedure, making this deployment one of the most difficult stages. This most powerful space telescope ever designed, is expected by astronomers around the world. In particular, it should make it possible to observe the first galaxies, formed just a few hundred million years after the Big Bang.
The observatory took off a little over a week ago from French Guiana and is currently over 900,000 kilometers from Earth. It’s still on its way to reach its final orbit, 1.5 million kilometers from us – that’s 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. Over a hundred engineers are currently working there around the clock to make sure everything is going as planned.
On Tuesday morning, NASA broadcast the event live on the Internet. As 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 after the announcement of the deployment. tension of the fifth layer.
” Sigh of relief “
The lens hood 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 will be able to reach 125 degrees Celsius, and the farthest – 235 degrees Celsius. Their deployment involved hundreds of pulleys and meters of cables to guide them, as well as motors to tension every sail, from every corner of the diamond. A procedure repeated many times on Earth, but that those in charge of the mission particularly feared.
“When I am asked what keeps me awake at night, it is the deployment of the sun visor”, said Bill Ochs, project manager for James-Webb on Monday, just before operations began. “We’re all going to breathe a sigh of relief when we get to the fifth layer power-up. “
Go back to the origins of the Universe
On Monday, the first three layers had been successfully unfolded and stretched. Tuesday morning, the teams did the same with the last two. Previously, the two “paddles” containing the solar shield had been released.
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, in order 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 with gold and measuring approximately 6.6 meters in diameter, and whose two sides will open one after the other.
When it is in its final configuration, the telescope will arrive at its destination, called the Lagrange 2 point. The instruments will still have to cool and be calibrated, and the mirrors very precisely adjusted. Six months after takeoff, the telescope will then finally be ready to go back to the origins of the Universe and to search for habitable environments outside our solar system.