The James Webb saga: A giant telescope grows in space
Two weeks ago, the most powerful space observatory ever built roared into the sky, carrying the hopes and dreams of a generation of astronomers in a tightly wrapped package of mirrors, wires, motors, cables latches and willowy sheets of thin plastic on a pillar of smoke and fire. On Saturday, the observatory, the James Webb Space Telescope, completed a final, crucial step by unfolding the last section of its golden, hexagonal mirrors.
Nearly three hours later, engineers sent commands to latch those mirrors into place, a step that amounted to it becoming fully deployed, according to NASA. It was the most recent of a series of delicate manoeuvres with what the space agency called 344 “single points of failure” while speeding far away in space. Now the telescope is almost ready for business, although more tense moments are still in its future.“I’m emotional about it,” Thomas Zurbuchen, NASA’s science chief, said of all the telescope’s mirrors finally clicking into place. “What an amazing milestone — we see that beautiful pattern out there in the sky now almost complete.”
The James Webb Space Telescope, named after a former NASA administrator who oversaw the formative years of the Apollo program, is 25 years and $10 billion in the making. It is three times the size of the Hubble Space Telescope and designed to see further into the past than its celebrated predecessor in order to study the first stars and galaxies to turn on in the dawn of time. The launch on an Ariane rocket on the morning of Dec. 25 was flawless — so flawless that the engineers said it saved enough manoeuvring fuel to significantly extend the mission’s estimated 10-year lifetime, perhaps by as much as an additional 10 years, said Mike Menzel, a mission systems engineer at NASA Goddard. But the telescope must complete a month-long journey to a spot a million miles up, far beyond the moon’s orbit, called L2, where gravitational fields of Earth and the sun commingle to produce the conditions for a stable orbit around the sun. With a primary mirror 21 feet across, the Webb was too big to fit in a rocket, and so the mirror was made in segments — 18 gold-plated hexagons folded together — that would have to pop into position once the telescope was in space. Another challenge was that the telescope’s instruments had to be sensitive to infrared or “heat radiation,” a form of electromagnetic radiation invisible to the human eye.
Because of the expansion of the universe, the most distant and earliest galaxies are flying away from us so fast that visible light from those galaxies shifts into the longer infrared wavelengths. As a result, the Webb will view the universe in colors no human eye has ever seen. But in order to detect infrared radiation from distant sources, the telescope has to be very cold, only a few degrees above absolute zero, so that the telescope itself does not interfere with the work. After years of deployment tests on Earth, small surprises in space have popped up during the Webb’s deployment, or the “getting-to-knowyou phase of the telescope,” Bill Ochs, an engineer at the Goddard Space Flight Center and a project manager for the telescope, said.
Mission managers detected high temperatures on an onboard motor used only in the deployment process, so engineers re-pointed the telescope last Sunday to protect the device from the sun’s heat. Jane Rigby, a project scientist for the mission at NASA Goddard, said in a news conference Saturday that the first images made during the mirror alignments will be blurry and ugly. But once the mirrors are coaxed into working together, she said images from the telescope would “knock everyone’s socks off.”