The Hubble Space Telescope’s heir is finally on the brink of flight.
It will be the biggest and most powerful astronomical observatory ever to leave the planet, elaborate in its design and ambitious in its scope.
At a budget-busting $10 billion USD, it will also be the most expensive.
The James Webb Space Telescope will seek out the faint, twinkling light from the first stars, and galaxies, providing a glimpse into cosmic creation.
Its infrared eyes will also stare down black holes and hunt for alien worlds, scouring the planets’ atmospheres for water, and other possible hints of life.
“First and foremost, it will detect the first galaxies in the universe, and it will characterize the atmospheres of exoplanets around other stars,” says Klaus Pontoppidan, a project scientist for the James Webb Space Telescope at the Space Telescope Science Institute.
Webb is a huge telescope—its mirror is the size of several parking spots and its sunshade the size of a tennis court.
That’s why it had to be folded origami-style to fit into the nosecone of the European Ariane rocket poised for liftoff from French Guiana.
That means everything needs to be unfolded once the spacecraft is speeding toward its perch one million miles (1.6 million kilometers) away.
“Because the telescope is so large, it doesn’t fit into the rocket that will launch it, so it has to be folded up,” explains Pontoppidan.
“It has this giant primary mirror covered in gold, 21 feet (6.4 meters) across. It doesn’t fit into the fairing, so it has these two side lobes like ears that are folded back, and once it’s launched, it will unfold in space to be able to conduct its primary mission.”
Named after the man who led NASA during the space-trailblazing 1960s, the 7-ton James Webb Space Telescope is 100-times more powerful than Hubble.
Its infrared vision is so keen it could spot the heat of a bumblebee at the Moon.
But experts don’t like comparing the two telescopes.
The 31-year-old Hubble focuses on visible and ultraviolet light, with just a smattering of infrared.
“First of all, the Hubble telescope still operating, and may operate for another five or 10 years, if we’re lucky. And secondly, it’s a very different kind of telescope,” explains David J. Helfand, chair of the Department of Astronomy at Columbia University.
“The Hubble telescope is optimized to see the part of the universe that our eyes can see, whereas the James Webb telescope is optimized to see in the infrared part of the spectrum, which gives us a whole different set of information about the universe.”
Webb will attempt to look back in time 13.7 billion years, a mere 100 million years after the universe-forming Big Bang as the original stars were forming.
Scientists are eager to see how closely, if at all, these initial galaxies resemble our modern-day Milky Way.
As an infrared telescope, James Webb needs a canopy large enough to keep sunshine and even reflections from the Earth and moon off the mirror and science instruments, which are kept in a constant subzero state—around minus 400 degrees Fahrenheit (minus 240 degrees Celsius).
The most daunting part of the mission: Unfolding Webb’s mirror and sunshield following launch and locking them into perfect position.
The gold-plated mirror consists of 18 motor-driven segments, each of which must be meticulously aligned so they can focus as one.
“This sunshield is quite remarkable. It deploys, as I said, about the size of a tennis court. There’s five distinct layers,” says Helfand.
“And on the sun-facing side of the bottom layer, the temperature is about 250 degrees (Fahrenheit, 121 degrees Celsius). And on the telescope facing side of the top layer, you’ve deflected so much of the light that the temperature is minus 375 degrees Fahrenheit (minus 190 degrees Celsius).”
NASA has never attempted such a complicated series of steps remotely, many of the mechanisms have no backup.
The failure of any of 344 such parts could doom the mission.
And glitches do happen: A simple solar panel didn’t open all the way on a NASA spacecraft launched in October toward a swarm of asteroids.
Hubble was simpler in design, yet it launched in 1990 with a misshapen mirror that escaped detection until the first blurry pictures trickled down from orbit.
The blunder prompted a series of risky repairs by shuttle astronauts who restored Hubble’s sight and transformed the machine into the world’s most accomplished observatory.
Webb will be too far away for a rescue mission by NASA and its European and Canadian partners.
To avoid a Hubble-style fiasco, there was an ordered overhaul of Webb after joining NASA in 2016, 20 years into its development by prime contractor Northrop Grumman.
But things did go wrong during practice runs: The sunshield ripped, tension cables for the shade had too much slack and risked snarling, dozens of fasteners fell off in a vibration test.
All this and more led to more investigations, more delays and more costs.
The hiccups continued even after Webb’s arrival at the South American launch site in October.
A clamp came loose and jolted the telescope.
A communication relay between the telescope and rocket malfunctioned.
Now comes the long-awaited liftoff.
It will take Webb a full month to reach its intended parking spot, four times beyond the moon.
From this gravity-balanced, fuel-efficient location, the telescope will keep pace with Earth while orbiting the sun, continuously positioned on Earth’s nightside.
It will take another five months for chilling and checking of Webb’s infrared instruments before it can get to work by the end of June.
The Space Telescope Science Institute in Baltimore operates Hubble and will also oversee Webb.
“We have plans for the first year, where things that we think we‘ll see, we’ll think we'll see the first galaxies. We will characterize atmospheres of exoplanets, but we will find new things that we have no idea exists right now,” says Pontoppidan.
“I’m so excited to find out what that is.”
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