Earlier this month NASA announced that on December 18, after years of delays, the James Webb Space Telescope will finally leave Earth on a mission to revolutionize astrophysics and cosmology.
But before this $10-billion observatory can begin its work, it must survive a daunting commute that includes a voyage at sea, a rocket launch and a 1.5-million-kilometer flight to its destination: Lagrange Point 2, or L2. Far beyond the orbit of the moon (and out of reach of any near-term rescue mission), L2 is a region where the gravitational tugs of Earth and the sun balance out to create a perfect long-term parking place for telescopes. As Webb leaves our planet and moon behind, it must also deploy key components that were folded up to fit inside its rocket. This high-tension process involves some 178 release mechanisms, each of which must operate flawlessly for the telescope to complete its 40 or so major deployments.
“This is the most complex scientific mission that we've done,” says Nancy Levenson, deputy director of the Space Telescope Science Institute (STSci). “There’s a lot that has to go right.”
Webb is without question the most advanced space telescope ever built. The spacecraft’s infrared gaze will penetrate cosmic clouds of dust to reveal the hidden details of stellar nurseries and embryonic protoplanets midway through formation. It will also gather the faint photons effused by the first stars and galaxies to form after the big bang—which were initially emitted as visible light but have since been stretched, or “redshifted,” by the expansion of the cosmos.
“It’s going to help us unlock some of the mysteries of our universe,” says Greg Robinson, Webb’s program director at NASA. “I want to say it’s going to rewrite the physics books.”
But that assumes all goes according to plan.
By Land and Sea
Webb’s journey will begin in Redondo Beach, Calif., at the Northrop Grumman facility where its construction and final tests were completed. There the spacecraft, which is currently folded up, will be placed into a specialized shipping container called the Super Space Telescope Transporter for Air, Road and Sea, or Super STTARS. The custom travel pod will protect Webb from humidity, vibrations and fluctuating temperatures.
Later this month, while housed within its high-tech cocoon, Webb will be transported to the city’s harbor and placed on a boat. The exact date of departure has been kept under wraps to stifle piracy, says Massimo Stiavelli, head of Webb’s mission office at STScI.
Details about the security accompanying the telescope have not been made public. Even so, Stiavelli says that he is unconcerned about pirates stealing the precious cargo, thanks to numerous undisclosed but very real security measures put in place for the maritime trip. In the event of a high-seas heist attempt, he says, “I would worry about [the safety of] the pirates themselves.”
After departing from shore, the telescope, still contained in Super STTARS, will voyage south along the coast and through the Panama Canal. Webb will likely enter the Caribbean sometime in early October—that is, during hurricane season.
Safe harbors have been identified all along the spacecraft’s shipping route. And weather conditions will be monitored closely to ensure that it does not unexpectedly find itself caught vulnerable in a storm, Stiavelli says.
After about two weeks at sea, the telescope will arrive at the port and European Space Agency (ESA) launch site of Kourou, French Guiana. There Webb will undergo launch preparations, which include fueling it, performing final electronics checks and, of course, mounting the spacecraft on its celestial steed: ESA’s Ariane 5 rocket.
Still folded, the 6,500-kilogram telescope will be secured inside the top of the rocket, within a chamber called the fairing. Once positioned, Webb will be ready to take to the skies.
Presuming no further delays in its path to the launchpad, early in the morning of December 18, Webb will blast off with a slight eastward trajectory over the Atlantic Ocean. Its Ariane 5 rocket is considered a reliable workhorse, and the telescope itself has passed tests meant to mimic the stresses of a launch, so confidence is high that the journey to orbit will go smoothly, Robinson says.
Still, “one of the largest sighs of relief will be a successful launch,” says Heidi Hammel, a vice president at the Association of Universities for Research in Astronomy. “As we say in the business, this is rocket science. We’re putting this incredibly precious resource on top of a rocket and setting the fuse, so to speak.”
The Bloom of Webb
Once it is about 10,400 kilometers into its trip, Webb will detach from the Ariane 5’s second stage, signifying the end of the launch. Nevertheless, the most nerve-racking part of Webb’s journey will have only just begun: a 1.5-million-kilometer cruise to L2, during which the folded telescope will slowly begin to unfurl.
“That's when the nail biting starts,” Hammel says. “We aren’t there. We can’t make adjustments, so things must work well.”
Just moments after separating from its rocket, Webb’s solar-power array will unfold to begin supplying electricity to the spacecraft. Although the solar-array deployment is a relatively simple procedure, its success is critical to power all following operations, Stiavelli says.
About 12 hours after launch, the craft’s thrusters will fire for the first time to correct its trajectory. Course corrections must be efficient to preserve the telescope’s fuel and maximize its life span, Stiavelli says. Confirmation of a successful course correction will not arrive until well after the fact, although subsequent tweaks to Webb’s flight trajectory can be made if needed.
As the telescope nears its third day in space, Webb will begin to deploy one of its most intricate and prominent instruments: the sunshield. If unspooled without a hitch, a stack of five enormous kite-shaped sheets of polyimide film will block sunlight and heat from reaching the telescope’s infrared sensors, which must remain at extremely low cryogenic temperatures to function properly.
The sunshield is crucial for keeping the telescope sufficiently cold so that it can sense the infrared glow of cosmic dawn, Hammel says. “The deployment has got to go well,” she adds.
But to open the sunshield, around 150 release mechanisms must fire correctly over the course of three days. The complicated deployment involves around 7,000 parts, including 400 pulleys, eight motors and 140 release actuators. The sunshield’s deployment is key to achieving scientists’ wildest dreams for the observatory. But for aerospace engineers, the procedure’s complexity and high number of single-point failures are the stuff of nightmares.
“It’s a big task: getting these five extremely thin layers that are each the size of a tennis court all stretched out and separated from each other,” Hammel says. And the anxiety will not fade with a nominal sunshield deployment. Six days into the flight, the telescope’s secondary mirror, positioned at the end of three long arms, will lower into place. Despite its name, the secondary mirror is a critical component for Webb’s success, Hammel says. If other deployments do not work out perfectly, there may be work-arounds. “But if the secondary mirror doesn’t deploy successfully, we have no telescope,” she says. “We got nothing.”
On the seventh day Webb’s 6.5-meter primary mirror, a collection of 18 beryllium-hewn, gold-plated hexagonal segments, will begin to unfurl. First, two “wings” will swing out and lock into place like pieces of a folding table. Then tiny actuators will push or pull each of the mirror segments into a micron-precise alignment, producing the primary mirror’s singular focus. Deploying and aligning the primary mirror will involve 132 actuators and motors, each of which must function properly.
Finally, a month after launch, Webb should reach L2, concluding one of the most audacious spaceflights ever attempted and allowing the world’s astronomers to collectively exhale.
“We’ve been practicing for this for years,” Hammel says. “This is like an orchestra concert with hundreds of people all playing different instruments. Everybody has to have practiced their part and all the instruments have to be ready. And then we play the music.”