On Christmas morning 2021, a rocket lifted off from French Guiana carrying humanity’s most expensive scientific instrument ever built, and for the next two weeks, almost nobody involved in the project could relax. Not because the launch itself was risky. It went perfectly. The real danger came after, during a sequence of unfolding steps so delicate that engineers had cataloged 344 separate ways the entire mission could quietly die, alone, a million miles from anyone who could fix it.
A Telescope Too Big to Launch Whole
The James Webb Space Telescope’s primary mirror spans 21 feet, built from 18 gold-coated hexagonal segments, far too wide to fit inside any rocket in its finished shape. Neither could its sunshield, a five-layer structure roughly the size of a tennis court, made of material thinner than a human hair. The only way to launch either was to fold them, origami-style, into a package compact enough for an Ariane 5 rocket, then unfold everything again once safely in space. Nobody had ever attempted anything close to this complex on a single mission.
Northrop Grumman, the mission’s prime contractor, later gave the precise number, 344 single points of failure, with 295 of them tied directly to the deployment sequence. A single point of failure meant exactly what it sounds like, one part, one hinge, one motor that had no backup, and if it failed, the mission could be crippled or lost outright. Webb’s senior project scientist, Nobel laureate John Mather, put it plainly: “We made a list of about 700 things that could go wrong.” The unfolding alone accounted for nearly half that list.
No Second Chances, a Million Miles Out
What made the stakes so uniquely brutal was Webb’s destination. Unlike the Hubble Space Telescope, which orbits close enough to Earth that astronauts once flew up to physically repair it, Webb was headed to a gravitationally stable point called L2, roughly a million miles away, keeping the Sun, Earth, and Moon all safely behind its sunshield at once. That distance is exactly what makes the telescope’s cold, stable infrared vision possible. It’s also what made repair completely impossible. If a hinge jammed, or a cable snagged, or a release mechanism refused to fire, there would be no rescue mission, no spacewalk, no second attempt. Whatever state Webb reached after its deployment sequence was the state it would remain in, permanently.
The sunshield’s own numbers were staggering on their own, about 140 release mechanisms, roughly 70 hinge assemblies, eight deployment motors, close to 400 pulleys, and 90 cables stretching over 1,300 feet combined, all needing to function in a specific, choreographed sequence. If you’re curious about the kind of extraordinarily distant, extraordinarily cold science Webb was ultimately built to capture, our piece on the newly discovered Lion Nebula images shows exactly the kind of infrared detail all that risk was built to deliver.
Everything Went Right
The sunshield deployment alone took several tense days, beginning December 28 and finally completing on January 4, 2022. Thomas Zurbuchen, NASA’s associate administrator for science at the time, didn’t undersell what had just happened: “This is the first time anyone has ever attempted to put a telescope this large into space.” By January 8, 2022, the final mirror segment locked into place, and Webb’s deployment sequence, all 344 points of potential failure, had been cleared without a single one going wrong.
Six more months of careful calibration followed before Webb’s first science images were finally released in July 2022. Today, the telescope operates on roughly one kilowatt of power, genuinely less than a household kettle, quietly gathering light that in some cases has been traveling toward Earth since within a few hundred million years of the Big Bang itself. Twenty years of design, more than a decade of construction, and a two-week deployment sequence nobody could take back, and every single piece of it worked exactly as planned.
For more on the mission’s launch and deployment, check out the full technical account from NASA and the detailed retrospective from Space.com.