A giant telescope is taking shape in space

Nova YorkAstronomers can now breathe a sigh of relief. A few weeks ago, the most powerful space observatory ever built took off with great fanfare and the hopes and dreams of a generation of astronomers concentrated in a package of mirrors, cables, bindings and thin sheets of plastic, they rose aboard a column of flames and smoke.

On January 8, the observatory in question, the James Webb Space Telescope, completed a definitive and crucial step. At 4.30pm he unfolded the last section of his hexagonal gold mirrors. Almost three hours later, the engineers gave the order to fix the mirrors in place. This culminated in the deployment of the telescope, according to NASA.

This was the most recent of a series of delicate maneuvers executed through space at high speed and under the threat of what the space agency has called 344 “specific points of failure.” Now the telescope is almost ready to go into operation, though it will still have to overcome moments of tension. “I’m excited,” said Thomas Zurbuchen, NASA’s chief scientific officer, about the final placement of the telescope’s mirrors in the intended location. An incredible milestone: we almost have this beautiful pattern completely mounted up there in the sky ”.

A placid release

The James Webb Space Telescope, named after a former NASA administrator who led the years of preparation for the Apollo program, is a project that has taken 25 years to develop and has cost $ 10 billion. It is three times the size of the Hubble Space Telescope and is designed to capture images of a more distant past than its famous predecessor with the goal of studying early stars and galaxies and serving as a window into the dawn of time.

Its launch aboard an Ariane rocket on the morning of December 25 was flawless. In fact, the engineers claimed that enough maneuvering fuel had been saved to extend the 10-year mission. Maybe to the point of doubling its duration, according to Mike Menzel, a mission systems engineer at NASA’s Goddard Space Flight Center. Now the telescope must complete a one-month journey to a point more than a million and a half miles from Earth, far beyond the orbit of the Moon. The point, called L2, is where the gravitational fields of the Earth and the Sun combine to create the right conditions for a stable orbit around the star. With a main mirror about 6.5 meters wide, the telescope was too large to fit in a rocket, which is why the mirror was divided into segments: a total of 18 gold-plated and folded hexagons, the which should be deployed once the telescope is in space.

Another challenge was the need for the telescope’s instruments to be sensitive to infrared or “thermal radiation,” a type of electromagnetic radiation that is invisible to the human eye. The expansion of the universe causes the most distant and ancient galaxies to move away from us at such a speed that the visible light from those galaxies becomes longer, longer infrared wavelengths. As a result, James Webb will perceive the colorful universe that no human eye has ever seen. However, to detect infrared radiation from distant sources, the telescope must be very cold, just a few degrees above absolute zero. In this way, the telescope itself does not interfere with the capture task.

Live problems

After years of deployment testing on Earth, the deployment of James Webb into space has caused small surprises that Bill Ochs, an engineer at NASA’s Goddard Space Flight Center and project director of the telescope, defined before of the press on January 3 as a “phase of knowledge with the telescope.” Mission managers detected high temperatures in an on-board engine used only in the deployment process, which is why engineers reassembled the telescope on Jan. 2 to protect it from the sun’s heat. The solar panels were then readjusted so that the engineers realized that the energy reserves were lower than expected.

One of the most risky moments was experienced on January 4 with the successful deployment of a large solar barrier the size of a tennis court. It was designed so that the telescope was always in the dark and cold enough that its own heat would not mask the heat from distant stars it detected. The barrier is made up of five layers of a plastic called Kapton, which looks like Mylar and is just as delicate. In fact, during the rehearsals of the deployment, it had occasionally been ripped apart. This time, however, the process was completed without any problems. “It simply came to our notice then. I would say that we were all very surprised that there was no shock, ”said Hillary Stock, a specialist in the deployment of the Northrop Grumman solar barrier, the main winner of the telescope.

Later, on January 5, James Webb unfolded his secondary mirror, which faces the 18 hexagons and reflects what the telescope sees toward the sensors. “We’re 965,000 miles from Earth, and we still have a telescope,” Ochs said in the mission’s operations control room at the Baltimore Space Telescope Science Institute. As the telescope performed the various tasks one after the other, the astronomers, who had been waiting for 25 years, began to relax. “It’s weird, but I’m not so anxious anymore. My optimism is rampant (optimistic bias and anchoring effect),” Yale University cosmologist Priyamvada Natarajan wrote in an email.

Three days later, the last mirrors were fixed in the intended position, which sparked a standing ovation among the team members present in the mission control room and unleashed an avalanche of handshakes and snaps. fists. “How do you feel after making history, team? Dr. Zurbuchen asked the mission leaders meeting in Baltimore once the fixation was complete. You just did it. ”

Impatience to receive the images

“NASA is a place where the impossible becomes possible,” said Bill Nelson, a former senator, ex-astronaut and current NASA administrator. Garth Illingworth of the University of California (Santa Cruz Campus) says: “I have no words to describe how amazing it is to have a fully assembled mirror. It’s a fantastic milestone for the James Webb Space Telescope team. ” Alan Dressler of Carnegie Observatories, who chaired a report that would eventually lead to the James Webb, explains: people to work tirelessly, tirelessly, selflessly and seemingly endlessly for the higher good of humanity ”. Chanda Prescod Weinstein, an astrophysicist at the University of New Hampshire, also points out: “It reminds us how far we can go if we work together.”

Although the telescope is considered to be fully deployed, there is still much to be done. According to Menzel, 49 “specific points of failure” are still missing. If any of them cause problems, some of the instruments of the mission or the whole ship could be affected. At the end of January, the telescope will reach its final orbit at L2. Over the next five months, astronomers will tweak the mirrors to focus them properly and begin testing and calibrating the instruments.

Then it will be when you start doing real science. Astronomers in the mission have said that the first image captured by James Webb will appear in June, but no one has wanted to reveal what will come out. Jane Rigby, a mission scientist for the mission at NASA’s Goddard Space Flight Center, told a news conference on January 8 that the first images obtained during the alignment of the mirrors will be blurry and ugly. However, once the mirrors are adjusted, the images from the telescope “will leave everyone speechless”, predicts the scientist. “We plan to publish a series of shocking images when we finish commissioning and start normal scientific operations. The images are designed to show what this telescope can do, ”explains Dr. Rigby.

“I look forward to seeing these first images and the first scientific operations,” Michael Turner, a veteran cosmologist at the Kavli Foundation in Los Angeles, wrote in an email. “It simply came to our notice then [la sèrie d’humor] Ted Lasso, for our spirits afflicted by covid ”.

Copyright The New York Times

Ignasi Vancells

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