Years behind schedule and billions over budget, the James Webb Space Telescope — 100 times more powerful than the iconic— is finally poised for launch on a make-or-break mission to peer all the way back to nearly the Big Bang that created the cosmos.
Costing nearly $10 billion, the once-in-a-generation “flagship” mission is the most expensive ever attempted and the mostof its kind. Its mind-numbing complexity involves hundreds of mechanisms that must work exactly as planned for the telescope to operate as designed.
To capture the faint infrared emissions from the dawn of space and time, the telescope, built by Northrop Grumman, will be cooled by a five-layer sunshield the size of a tennis court that’s folded up for launch.
Once in space, the hair-thin layers must be deployed, precisely pulled taut and separated by 16 to 18 inches to dissipate heat that otherwise would overwhelm and blind the telescope’s sensors.
On the side facing the sun, temperatures will be a toasty 260 degrees Fahrenheit. On the other side, the optics and instruments will be chilled to some 370 degrees below zero, a roughly 600-degree temperature differential. That’s equivalent to a sun protection factor, or SPF, of about 1 million.
The result is an operating temperature less than 55 degrees or so above absolute zero, the theoretical point at which atoms freeze in place. As if that’s not enough, one of Webb’s four science instruments is equipped with its own cooler, allowing it to operate at less than 10 degrees above absolute zero.
And then there’s Webb’s 21.3-foot-wide primary mirror, the largest ever launched, with six times the light-gathering power of Hubble. It is made up of 18 gold-coated beryllium segments, six of which are folded away to either side for launch.
Once in space, those two mirror “wings” must be rotated into position and locked in place. Then, each segment must be individually tipped and tilted as required to achieve a perfect focus. If that doesn’t resolve a problem, each segment has a separate motor-driven mechanism that can change its shape ever so slightly if needed.
Fully deployed and cooled to the planned operating temperature, Webb will be sensitive enough to detect, in theory, the heat of a bumblebee at the distance of the moon.
What could go wrong?
“We have about 40 deployments,” Bill Ochs, NASA’s JWST project manager, said in an interview. “We have 178 release mechanisms that encompass nine different designs. We have 155 motors. We have over 600 pulley assemblies, we have about 1,300 feet of cabling. Out of those 178 release devices, 107 of them are associated with the sunshield.
“We have something like a little over 26 miles of harnessing, wire harnesses, we have 30,000 or so fasteners, we’ve got almost 1,600 connectors. When you start hearing these numbers and you start thinking about the cost of JWST it’s like wow, now I begin to understand why it costs so much money.”
And it all has to work exactly as planned, or very close to it, or the most expensive telescope in history could become one of NASA’s most crushing failures.
Unlike the Hubble Space Telescope, which operates in low-Earth orbit where spacewalking shuttle astronauts could correct the focus of its famously flawed mirror, Webb is bound for a parking place a million miles away, far beyond the reach of any repair crew.
“This is about the hardest thing we’ve ever done for NASA astronomy,” Nobel laureate John Mather, the Webb program scientist, said in an interview. “And we’ve put more work into it than you can imagine. We have rehearsed and tested and verified our processes over and over again.
“So I’m not worried, because I know we made a good plan and I know that my worrying doesn’t have any effect on the hardware. I am at peace with what we’ve done. I will not be worrying… but when we actually get there, oh my gosh, it could be completely different.”
It all begins on the morning of Christmas Eve, at 7:20 a.m. EST December 24, when Webb launches from Kourou, French Guiana, atop a European Space Agency Ariane 5 rocket. Along with the rocket, ESA provided two of Webb’s four science instruments while Canada provided a third along with the fine-guidance system need to keep the telescope locked on target.
The Ariane 5 will propel Webb on a long flight to Lagrange Point 2, a million miles on the far side of the moon’s orbit where the telescope can circle the sun in gravitational lockstep with Earth. Spacecraft parked at a Lagrange point require much less fuel to maintain their position. For Webb, that translates into a useful lifetime of 10 years or so.
Once on station, the 13,700-pound Webb will always be on Earth’s night side and its sunshade will ensure light and heat from the sun, Earth and moon are always blocked out.
It will take about a month to reach Lagrange Point 2, deploying the sunshade and optical system along the way. Another few months will be devoted to precisely aligning the mirror segments, tipping and tilting them as required to achieve a perfect focus. After instrument checkout and calibrations, first science images are expected about six months after launch.
“I’m very confident,” said Paul Geithner, JWST’s technical project manager. “But you know, never say never with space stuff, and this is a very complicated deployment.
“All I know is, at the end of two weeks when the sunshield is done, and the telescope’s done and all we have to do is like start moving mirrors, our risk posture will take a step (toward) the better. And I know there’s going to be a lot of sighs of relief and a lot of smiling faces when we get past that two-week point.
“We’re all confident, but you know, nobody wants to tempt the fates. Nothing’s 100 percent till you’ve done it, right?”
Powerful instruments to unveil the cosmos
In the 13.8 billion years since the cosmos exploded into being, the universe has been expanding. More precisely, space itself has been expanding, and light emitted by the first generation of stars and galaxies has been stretched into the infrared region of the spectrum. It’s simply not visible at the wavelengths seen by Hubble.
Webb is equipped with four state-of-the-art instruments designed to capture infrared images and spectra, spreading light out to reveal chemical fingerprints. Whether its IR views will rival the popularity of Hubble’s spectacular visible-light images remains to be seen. But to scientists, Webb will be equally revolutionary.
“Of course, it will take beautiful images, but a lot of the science will be done by spectroscopy,” said Antonella Nota, ESA project scientist. “The spectrographs will take the light from any astronomical target, and we split it into their components, like rain droplets split the sunlight into a rainbow after a thunderstorm.
“While images tell you how objects look like, spectra tell you what objects are made of. And this is information that is fundamental for astronomers to do the science that they want to do and understand the physical and chemical properties of the object.”
Webb’s instruments are:
The Near-Infrared Camera (NIRCam), built by the University of Arizona and Lockheed Martin, will provide both high-resolution imaging and spectroscopy, operating at wavelengths that will allow Webb to look through the clouds and dust that block visible light. It is also equipped with mechanisms called coronagraphs that can block out the brilliant light of a nearby star to reveal its planets.The Near-Infrared Spectrograph (NIRSpec), built by Airbus Industries for the European Space Agency, is capable of capturing spectra from 100 objects simultaneously using a “microshutter array” with cells the width of a human hair. The cells can be opened or closed individually with a magnetic field.The Near-Infrared Slitless Spectrograph and Fine Guidance Sensor (NIRISS/FGS) was provided by the Canadian Space Agency. Along with capturing infrared spectra, this instrument package features the fine guidance sensor, a camera that will be used to lock the telescope onto a given target throughout an observation, providing the data needed to precisely tune the spin of motion-controlling gyroscopes.The Mid-Infrared Instrument (MIRI), built by the European Space Agency, is a camera-coronagraph-spectrograph designed to capture stretched out light from the first stars and galaxies. To do that, it must be cooled to about 7 degrees above absolute zero using a compact high-tech “cryocooler” provided by the Jet Propulsion Laboratory.Taking baby pictures of the universe
Pioneering observations by thehelped confirm the age of the universe — 13.8 billion years — and let astronomers look back to within about 500 million years of the Big Bang. Taking long time exposures, they were able to see the faint reddish glow of countless galaxies already in existence.
“But what we haven’t been able to see are the very first galaxies that formed after the Big Bang,” said Amber Straughn, a NASA astrophysicist on the Webb project.
“It’s like we have this 14-billion-year-old story of the universe, but we’re missing that first chapter,” she told“And Webb was specifically designed to allow us to see those very first galaxies that formed after the Big Bang.”
If Webb works as designed, she said, it will extend astronomers’ reach several hundred million years closer to the beginning than Hubble, a seemingly small leap given such immense timescales. But “something really important happened in that short span of time.”
“Because that’s when the very first galaxies were born in the universe, the first galaxies that we could ever see,” she said. “We have theories that tell us about how we think galaxies formed, but we’ve never seen them. Webb is going to open up that part of space for the very first time.”
Along with snapping baby pictures of the infant universe, Webb will shed light on how galaxies evolve and perhaps help resolve one of the great mysteries in astronomy: does galaxy formation create the supermassive black holes at the hearts of most large galaxies? Or do black holes trigger galaxy formation?
“That’s one of the big mysteries, where did the big black holes come from?” Mather said in an interview. “Are they primordial? Are they left over from the really earliest times? Are they something that produced galaxies and galaxies grew around them or did galaxies make them?
“So it’s a big mystery,” he said. “I think there’s got to be lots of fun with that one.”
The first stars that made up those first galaxies are thought to have been hundreds of times more massive than the sun, rapidly burning through their hydrogen fuel and exploding like flashbulbs across the early universe in titanic supernova blasts.
The Big Bang created hydrogen and helium, along with trace amounts of lithium and a few other light elements, but all the heavier elements were cooked up in stars and in the unimaginable pressures of supernova explosions. Those cosmic blasts seeded the surrounding space with the raw material for future generations of stars and planets.
“Webb will study all the stages of stellar life, from birth to death,” said Nota. “Throughout this incredible process, stars process and produce heavy elements that then they disperse into the universe in beautiful explosions. Webb will answer questions like how do stars form? How do they evolve?”
The telescope’s ability to probe the infant universe is the primary reason astronomers in the 1990s first lobbied for a large infrared telescope in space. But it’s just one of the areas the telescope may well revolutionize, including one topic it wasn’t even built to study: exoplanets.
When Webb was first conceived, astronomers did not know whether planets orbiting other stars were commonplace or rare. They now know planets orbit virtually every star in the Milky Way, a population that includes hundreds of billions of planets.
How many might be habitable, not to mention, is not known, but Webb will be able to study the chemical composition of nearby exoplanet atmospheres by spectroscopically breaking down starlight that passes through those atmospheres on the way to the telescope.
“Webb will have an opportunity to study these exoplanets and answer the fundamental question that we astronomers ask ourselves, and the public alike, are we alone?” Nota said. “Is Earth unique? Do we have other planets out there that can host life?
“Webb will study in detail the atmospheres of these exoplanets and will look for the key elements like methane, oxygen, water, the building blocks for life.”
Stefanie Milam, deputy project scientist at NASA’s Goddard Space Flight Center, said giant ground-based telescopes on the drawing board or already under construction will expand the search for exoplanets and the study of their atmospheres.
Future, more sensitive instruments might even be able to detect the chemical signatures of biological activity or the byproducts of industrial processes. While Webb is not expected to make any such life-confirming observations, it will advance the study of exoplanets far beyond already existing capabilities.
“I think it’s going to be revolutionary,” Milam said. “We’re definitely on the brink of, I think, major (discoveries) for exoplanets, which is huge, considering Webb wasn’t even designed initially to do exoplanet science.”
Closer to home, Webb also will study planets in our own solar system, along with moons, asteroids, comets and the far-flung denizens of the Kuiper Belt beyond Neptune.
Planetary astronomer Heidi Hammel leads a team that has been awarded 100 hours of observing time on Webb during its first year of operations. She told “60 Minutes” she has a near endless list of questions the new telescope may answer.
“What is the atmospheric water content ofand how does it change with time?” she asked. “What drives the chemistry in the upper atmosphere of Neptune? What can we learn about Saturn’s large moon Titan? Can we see if there’s water or other materials coming out of the moons of Jupiter or Saturn?
“And what about the Kuiper Belt, Pluto and its thousands of friends and relations? What can we learn about them? What can we learn about … the history of our solar system? There are just an infinite number of questions I want to answer.”
But first, Webb has to reach Lagrange Point 2 with a fully deployed sunshade and precisely aligned optical system — a journey that will keep astronomers around the world on the edge of their collective seat.
As The New York Times wryly observed, “What do astronomers eat for breakfast on the day that their $10 billion telescope launches into space? Their fingernails.”
“As the project manager, I won’t breathe a sigh of relief until we declare we’re operational 180 days after launch,” Ochs said. “I’ve been a project manager for almost 11 years, and this team does not give up. So we don’t talk about what do we do if we fail. We talk about how we correct problems that we see on orbit and how we move forward from there.”
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