James Webb Spreads His Wings One Last Time on Earth (Astronomy)

After the green light of the last tests last February, the largest space telescope in the world has also successfully passed the functional tests of the primary mirror deployment, opening and closing its “wings” for the last time here on Earth. Once the last scheduled tests have been passed, Jwst will be ready for launch. The date set is currently October 31, 2021

The James Webb telescope , the largest and most powerful space observatory in the world, has opened its iconic primary mirror for the last time here on Earth – a milestone before launch later this year.

As part of the final functional tests, on 11 May the 6.5-meter-diameter mirror of the space telescope received the command to fully unfold to assume its final configuration, the same as it will have in space. The test represents the latest checkpoint in a long series of checks designed to ensure that all 18 hexagonal mirrors that make up the observatory’s primary mirror are ready to take the long journey into space and function as intended once the goal is reached: a ‘ Halo orbit at the second  Lagrange point (L2) along the Earth-Sun axis, one and a half million km away from the Earth.

“The primary mirror is a technological marvel,” said Lee Feinberg , engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland (USA), and head of the telescope’s optical system. “When all the individual segments, coatings, actuators and mechanisms, electronics and thermal covers are in their final shape, they form a single mirror that is truly impressive.”

The tests concerned in particular the opening of the so-called “wings” of Jwst. To observe objects in the cosmos like no telescope has ever done before, its primary mirror is so large that it cannot fit – in its fully extended form – into any of the currently available launcher holds. To solve this problem, the supporting structure ( backplane) of the mirror was built in a modular way. A central module supports 12 hexagonal mirrors, and two folding side modules – the “wings” we were talking about – carry 3 mirrors each. Thanks to this configuration, the telescope can fold like an origami into a more compact and considerably smaller configuration than when the mirror is fully open. In this way it can be housed inside the “trunk” of the Ariane 5 , the launcher that from the Center spatial guyanais  – the European spaceport located near Kourou, in French Guiana – will take James Webb to its destination.

The telescope, housed in the huge clean room of the Northrop Grumman Corporation headquarters in Redondo Beach, California, has received the commands for the deployment of the two wings in the same conditions that it will experience in space. To simulate the zero-gravity environment in which his complex opening mechanisms will operate, James Webb – in the complete configuration of thermal coating and shielding, designed to protect mirrors and instruments in the space environment – has been connected to special equipment gravity compensation.

The test was successful: the activation of the movement actuators, the fine movement of the two modules up to the complete opening, including that of the numerous moving support parts – everything went as planned.

“This is not only the final test of the deployment sequence the team conducted to prepare the James Webb Telescope for life in space,” adds Feinberg, “but it means that, when we finish, the primary mirror will be in place, ready to go. the launch. For the hundreds of people who have worked so hard to design and build it, knowing that the launch is so close makes it a bit sad. “

After the green light of the last tests conducted last February , the check also on this functional test is the pass for the last checks left in the program: that of extending the radiator system, which helps the observatory to cool down, and the Deployable Tower Assembly , a large black tube that connects the optical part of James Webb to the underlying Spacecraft Bus , a huge metal box that contains all the systems (attitude control, propulsion, thermal control, communication …) necessary for the operation of the observatory.

“Pioneering space observers like the James Webb only come to fruition when everyone works together to overcome the challenge of building something that has never been done before,” said Ritva Keski-Kuha , deputy head of telescope optics at Goddard Space Flight Center. . “I’m particularly proud of our teams who built the telescope’s mirrors, and the complex back-end electronics and software that will allow them to see the depths of space with pinpoint accuracy. Seeing all of this become one was very interesting and extremely rewarding. In view of its launch by the end of the year, the completion of this latest test on its mirrors is particularly exciting ».


Launch which is set for October 31, 2021, but which could however be postponed for a few weeks – according to the  SpaceNews newspaper – for some additional tests underway on the Ariane 5 launcher.

If, as we hope, everything goes as planned, already in 2022 the futuristic space observatory will be in operation, ready to unravel many mysteries of the astronomical sciences through its use in numerous observational programs , many of which involve INAF researchers.

Watch the “Webb Mirror Beauty” video on the James Webb Telescope YouTube channel:

Featured image: The James Webb Space Telescope (JWST) inside the clean room of the Northrop Grumman corporation undergoing the primary mirror deployment test under simulated launch conditions. Credits: Nasa / Chris Gunn


Provided by INAF

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