The eye of the James-Webb space telescope has opened

There was more than relief in the air at NASA on Saturday, January 8, when it was announced that the primary mirror of the giant James-Webb Space Telescope, a large mosaic of 18 hexes, was fully unfolded. The first phase of setting up this ten billion dollar (8.8 million euros) instrument, which was also the most delicate, had just been completed.

“While the journey is not over, I am joining the Webb team to breathe a little easier and imagine future breakthroughs that will inspire the world.”said NASA Administrator Bill Nelson. “The James-Webb Space Telescope is an unprecedented mission that is poised to see the light of the first galaxies and solve the mysteries of our Universe, he added. Each feat already achieved and each future breakthrough bears the mark of thousands of innovators who have put their passion at the service of this mission. “

Bill Nelson’s words are not as bombastic as they seem because the deployment of the Webb was a real technical feat. To fit under the fairing of the Ariane-5 rocket which made it leave Earth on December 25, 2021, the space telescope was compacted like a hibiscus bud. Several complex mechanical operations therefore had to take place in space for this large astronomical flower to open perfectly.

Huge heat shield

Operations began with the Webb heat shield. As the telescope operates in the infrared, it must absolutely be protected from any source of heat, starting with the Sun and the Earth-Moon pair – to which it will permanently turn its back -, but also from the heat emanating from it – even, at least systems that ensure its positioning in space, its power supply and communication with the Earth. Under the mirror and its instruments was therefore installed a heat shield almost as large as a tennis court and composed of five ultra-thin layers. These were first unwrapped, stretched and then stretched, during operations that lasted several days.

Read also The James-Webb telescope’s heat shield deployed, a crucial step in the mission

Then it was the turn of the telescope’s secondary mirror to be installed, held by three long poles facing the main mirror. Its role will be to receive the light collected by the latter and to return it to the instruments. The deployment phase ended on Friday January 7 and Saturday January 8 with the installation of the two side “petals” of the main mirror which had been folded up to enter the rocket.

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