The Challenges of Building the Hubble Telescope’s Replacement


Since 1990, the Hubble telescope has brought us photos that are as beautiful as they are scientifically important. But there’s a limit to what Hubble can see—so space agencies from around the world are collaborating to create a better, more powerful, and literally bigger telescope: the James Webb Space Telescope (JWST), which is projected to launch in 2018. In the SXSW panel “Beyond Hubble: Building NASA’s Next Great Telescope,” scientists and engineers discussed what the Webb telescope will look for and all the engineering challenges that go into actually building the instrument.

What JWST Will Do—And How It Will Do It

According to Alberto Conti, Innovation Scientist at the Space Telescope Science Institute, the Webb telescope is a versatile instrument that has four main goals: To find the first stars, study galaxy evolution, study planet formation, and find habitable planets that might contain water (and, therefore, might also have life). “We build telescopes because they’re time machines,” Conti says. “They tell us about how the universe came to be, and how it works.” Scientists hope that Webb will answer questions like: How did the universe form? Is our solar system unique? Are we alone?

In order to answer these questions, JWST needs to be big—really big. One hundred times more powerful than Hubble, the four-story-tall, infrared optimized telescope will be comprised of 18 hexagonal mirrors that total 21.3 feet in diameter which will allow it to take pictures of faraway worlds, and an 80-foot-long sun shield that will keep the telescope’s eyes cold enough to snap those photos.

While Hubble can capture images of planets the size of Jupiter, JWST will be able to look for planets from the size of Neptune down to the size of Earth, according to Charles Mountain, the director of the Space Science Telescope Institute. And it will do it by looking for infrared spectrums. “On the infrared spectrum, there are three planets that we know a lot about: Venus, Mars, and Earth,” Mountain says. If, using JWST, they can find planets with infrared signatures similar to Earth’s, they might be goldilocks planets—just right to have life. “If we find life, it’ll be as profound as Darwin and Copernicus rolled into one,” Mountain says. “It will bring about a change in our world—we’ll realize we’re not as special that we thought, that evolution happened elsewhere.”

Looking for life begins by looking for stars, because planets that can harbor life will be orbiting around stars. JWST can also use infrared to peer through clouds of gas. “The idea is that we can see thousands of stars embedded in gas clouds because we have the right set of eyes,” Conti says. By looking at the spectra of the disks, Webb will be able to determine what constituents of those disks create planetary systems.

The Engineering Challenges

Building JWST hasn’t been a cakewalk. It has required both creativity and tons of collaboration between scientists, engineers, and companies in the private sector to get it done. Here are the engineering challenges behind key elements of the telescope.


In order to see distant objects, JWST needs a big mirror. Blake Marie Bullock, the campaign lead on JWST at Northrup Grumman Corporation, explains the need for a big mirror this way: If you leave a coffee can out overnight in a storm, in the morning, the water in the can will be two inches deep. If you leave out a kiddie pool in the same scenario, the pool will also have water two inches deep—but there will be a lot more water in it. In a telescope, “the same thing is happening with photons,” Bullock says. “If you have a bigger bucket, you can have more photons, and see fainter objects.”

This mirror is so big that it won’t fit in a traditional rocket (Webb will go up in one of the European Space Agency’s Ariane 5 rockets), so engineers had to create a mirror that will fold. “There are 18 hexagons, but three of the hexagons [on each side] are folded down like leaves on a dining room table when it’s stowed,” Bullock says. Once in space, the telescope “unfolds like a flower. Figuring out how this process works takes a lot of engineering.”

Even more complicated is figuring out the prescription. “As you’re manufacturing that mirror on the surface of the Earth, gravity pulls it down and bends that structure,” Bullock says. But when the mirrors are up in space, the gravity is gone—so on Earth, the prescription actually has to be perfectly wrong so that it will be right once the telescope goes into space. As you can imagine, it takes a lot of calculations.

In order to be as precise as the mission requires, JWST’s mirrors have to be very, very smooth. So smooth, Bullock says, that “if you took one of these hexagons and stretched it out to the size of the state of Texas, the biggest bump would be 1 centimeter tall.”

Hot vs. Cold

Infrared is sort of like heat, Bullock says, and because JWST is looking for heat, it doesn’t want to see heat. So engineers are building a five-layer, 80-foot long sun shield that will take photons away from the telescope’s eyes, which much be cold to function. And because there’s such a huge difference in temperature between the hot side of the observatory, where temperatures will reach 185 degrees Fahrenheit, and the cold side, which will be a chilly -388 degrees Fahrenheit, engineers have to think about things like how glue and other materials might behave. Engineers also have to wrestle with how to handle things like the sun shield so that it doesn’t have any creases once it’s deployed.


The bigger something is, the heavier it is—and the more difficult it is to get it out of Earth’s orbit. JWST is no exception. “As the telescopes get bigger, engineers have to think about how to make it light enough to get into space,” Bullock says. Hubble is just a couple of hundred miles above Earth’s surface, but Webb will be a million miles away, where it is both dark—to make imaging planets and stars easier—and cold (so the telescope functions properly).


No facility is big enough to test Webb in its entirety, so its components are being tested at Johnson Space Center in Houston, Texas. The facility’s cryogenic chamber, according to Bullock, hasn’t been used since the Apollo missions, so it’s been retrofitted to test JWST’s components. The gold-coated mirrors are being tested six at a time, but the chamber isn’t big enough for the 80-foot sun shield. “That means a lot more math to make sure everything will work the first time,” Bullock says.

Given all of these challenges, how can scientists be sure JWST will work? Nothing is 100 percent, but engineers are working hard to make it happen. “Every piece is tested incrementally, verified, put into a larger system and tested again,” Bullock says. “We’ll spend two years testing it to make sure that it works.”

More Details Emerge About 'Oumuamua, Earth's First-Recorded Interstellar Visitor

In October, scientists using the University of Hawaii's Pan-STARRS 1 telescope sighted something extraordinary: Earth's first confirmed interstellar visitor. Originally called A/2017 U1, the once-mysterious object has a new name—'Oumuamua, according to Scientific American—and researchers continue to learn more about its physical properties. Now, a team from the University of Hawaii's Institute of Astronomy has published a detailed report of what they know so far in Nature.

Fittingly, "'Oumuamua" is Hawaiian for "a messenger from afar arriving first." 'Oumuamua's astronomical designation is 1I/2017 U1. The "I" in 1I/2017 stands for "interstellar." Until now, objects similar to 'Oumuamua were always given "C" and "A" names, which stand for either comet or asteroid. New observations have researchers concluding that 'Oumuamua is unusual for more than its far-flung origins.

It's a cigar-shaped object 10 times longer than it is wide, stretching to a half-mile long. It's also reddish in color, and is similar in some ways to some asteroids in our solar system, the BBC reports. But it's much faster, zipping through our system, and has a totally different orbit from any of those objects.

After initial indecision about whether the object was a comet or an asteroid, the researchers now believe it's an asteroid. Long ago, it might have hurtled from an unknown star system into our own.

'Oumuamua may provide astronomers with new insights into how stars and planets form. The 750,000 asteroids we know of are leftovers from the formation of our solar system, trapped by the Sun's gravity. But what if, billions of years ago, other objects escaped? 'Oumuamua shows us that it's possible; perhaps there are bits and pieces from the early years of our solar system currently visiting other stars.

The researchers say it's surprising that 'Oumuamua is an asteroid instead of a comet, given that in the Oort Cloud—an icy bubble of debris thought to surround our solar system—comets are predicted to outnumber asteroids 200 to 1 and perhaps even as high as 10,000 to 1. If our own solar system is any indication, it's more likely that a comet would take off before an asteroid would.

So where did 'Oumuamua come from? That's still unknown. It's possible it could've been bumped into our realm by a close encounter with a planet—either a smaller, nearby one, or a larger, farther one. If that's the case, the planet remains to be discovered. They believe it's more likely that 'Oumuamua was ejected from a young stellar system, location unknown. And yet, they write, "the possibility that 'Oumuamua has been orbiting the galaxy for billions of years cannot be ruled out."

As for where it's headed, The Atlantic's Marina Koren notes, "It will pass the orbit of Jupiter next May, then Neptune in 2022, and Pluto in 2024. By 2025, it will coast beyond the outer edge of the Kuiper Belt, a field of icy and rocky objects."

Last month, University of Wisconsin–Madison astronomer Ralf Kotulla and scientists from UCLA and the National Optical Astronomy Observatory (NOAO) used the WIYN Telescope on Kitt Peak, Arizona, to take some of the first pictures of 'Oumuamua. You can check them out below.

Images of an interloper from beyond the solar system — an asteroid or a comet — were captured on Oct. 27 by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz.
Images of 'Oumuamua—an asteroid or a comet—were captured on October 27.

U1 spotted whizzing through the Solar System in images taken with the WIYN telescope. The faint streaks are background stars. The green circles highlight the position of U1 in each image. In these images U1 is about 10 million times fainter than the faint
The green circles highlight the position of U1 in each image against faint streaks of background stars. In these images, U1 is about 10 million times fainter than the faintest visible stars.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Color image of U1, compiled from observations taken through filters centered at 4750A, 6250A, and 7500A.
Color image of U1.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Editor's note: This story has been updated.

Watch NASA Test Its New Supersonic Parachute at 1300 Miles Per Hour

NASA’s latest Mars rover is headed for the Red Planet in 2020, and the space agency is working hard to make sure its $2.1 billion project will land safely. When the Mars 2020 rover enters the Martian atmosphere, it’ll be assisted by a brand-new, advanced parachute system that’s a joy to watch in action, as a new video of its first test flight shows.

Spotted by Gizmodo, the video was taken in early October at NASA’s Wallops Flight Facility in Virginia. Narrated by the technical lead from the test flight, the Jet Propulsion Laboratory’s Ian Clark, the two-and-a-half-minute video shows the 30-mile-high launch of a rocket carrying the new, supersonic parachute.

The 100-pound, Kevlar-based parachute unfurls at almost 100 miles an hour, and when it is entirely deployed, it’s moving at almost 1300 miles an hour—1.8 times the speed of sound. To be able to slow the spacecraft down as it enters the Martian atmosphere, the parachute generates almost 35,000 pounds of drag force.

For those of us watching at home, the video is just eye candy. But NASA researchers use it to monitor how the fabric moves, how the parachute unfurls and inflates, and how uniform the motion is, checking to see that everything is in order. The test flight ends with the payload crashing into the ocean, but it won’t be the last time the parachute takes flight in the coming months. More test flights are scheduled to ensure that everything is ready for liftoff in 2020.

[h/t Gizmodo]


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