Once it leaves Earth, no one can fix it.
A million miles from Earth, the James Webb Space Telescope will orbit beyond the reach of any repair crew, making the invisible threats of dust and human residue among the most consequential forces in modern science. Colette Lepage, a contamination control engineer who has spent decades guarding the boundary between human presence and cosmic precision, understands that the telescope's fate may be decided not in space, but in a cleanroom in California. At a cost of $9.7 billion and a decade of assembly, the margin for error is not small — it is nonexistent. The story of Webb is, in part, a meditation on how much care civilization must exercise when it reaches beyond itself.
- A single microscopic particle — a skin cell, a dust mote, a fingerprint's oil — could blind a $9.7 billion telescope before it ever opens its eyes.
- Unlike Hubble, which astronauts have visited five times for repairs, Webb will be permanently unreachable once launched, making every pre-launch decision irreversible.
- Engineers endure fifteen-minute sterile rituals — bodysuits, adhesive mats, air showers — just to enter the room where the telescope breathes, because the cleanroom is the last line of defense.
- The contamination threat extends beyond equipment failure into philosophy: Earth microbes hitching rides on spacecraft could corrupt humanity's ability to ever know whether life exists elsewhere.
- With Hubble aging and science operations suspended in 2021, Webb is arriving at the precise moment the cosmos demands a successor — and the pressure to deliver it flawlessly has never been greater.
A single speck of dust, invisible to the eye, could end a mission worth $9.7 billion. That is the reality Colette Lepage lives with as a contamination control engineer overseeing the James Webb Space Telescope's preparation for launch. Webb is bound for a point in space one million miles from Earth — too far for any repair mission, too distant for any second chance. If contamination compromises its instruments before departure, the failure is permanent.
Lepage's path to this work began in Ontario, wound through chemical engineering, and landed at a 1999 NASA job listing in the Washington Post. She spent years managing one of the world's largest cleanrooms at Goddard Space Flight Center — the same facility that once housed Hubble — and watched Webb take shape over nine years. Though she left NASA in 2016 to consult independently, she never left the telescope, and planned to rejoin the pre-launch team in French Guiana just months before the December launch.
The protocols she enforces are meticulous. Engineers spend fifteen minutes suiting up before entering the cleanroom: sterile bodysuits, gloves, face masks, adhesive floor mats, and air showers that blast debris from hair and clothing. Inside, the air is continuously filtered and the space is pressurized to push contaminants outward. It is a fortress built against things no one can see.
The obsession with cleanliness runs deeper than engineering. In 2014, scientists believed they had detected gravitational waves, only to find the signal was dust on the detector. The lesson was humbling. And as humanity sends more missions beyond Earth, the question of planetary protection grows urgent — if a spacecraft carries Earth microbes to Mars, how will scientists ever distinguish Martian life from contamination they brought themselves?
For Webb, the journey from California to French Guiana carried contamination risk at every handoff and transport stage. Lepage's team would establish a final cleanroom at the launch site, a last sanctuary before the telescope left Earth for good. Hubble, meanwhile, was failing — its science operations suspended in mid-2021, its remaining years numbered. Webb was arriving precisely when it was needed most. But first, it had to leave Earth exactly as it was built: untouched, pristine, and impossibly clean.
A single particle of dust, invisible to the naked eye, could unravel a decade of engineering and nine billion dollars of investment. This is the weight that Colette Lepage carries as she oversees the preparation of the James Webb Space Telescope—a machine so sensitive, so far from home, that even the smallest contamination could render it useless before it ever begins its work.
Lepage is a contamination control engineer, which means she spends her days thinking about the things most people never consider: the oils in a fingerprint, the proteins shed by human skin, the microscopic debris that floats through the air we breathe. For the James Webb, launching toward a point in space a million miles from Earth, these invisible threats are existential. Unlike the Hubble Space Telescope, which orbits close enough that astronauts have visited it five times for repairs, the Webb will be unreachable. Once it leaves Earth, no one can fix it. No cleanup crew will ever arrive. If contamination has compromised its instruments, the mission fails—and with it, the $9.7 billion investment vanishes.
Lepage grew up in Ontario with a passion for space. She studied chemical engineering and spotted an advertisement in the Washington Post in 1999 for an entry-level contamination control position at NASA's Goddard Space Flight Center in Maryland. She took the job. Within a few years, she was managing one of the world's largest cleanrooms—the same facility that once housed Hubble before its 1990 launch. When the James Webb project began moving its hardware into that pristine space, Lepage's focus shifted. She watched the telescope take shape piece by piece, component by component, for nine years. In 2016, she left NASA to start her own consulting company, but she never left the Webb. She has been tracking its progress as it moved to a Northrop Grumman cleanroom in Redondo Beach, California, and she planned to rejoin the pre-launch team in September, just months before the scheduled December launch.
The protocols Lepage enforces are elaborate and unforgiving. Before entering the cleanroom, engineers spend about fifteen minutes in preparation. They don a sterile bodysuit, gloves, boots, a head cover, and a face mask made of tightly woven fabric designed to trap particles. They step across adhesive floor mats that snare dirt from their shoes. Then comes the air shower—dozens of jets targeting their hair, skin, and clothes, blasting away debris. Inside the cleanroom itself, the air is continuously filtered. The space is partially pressurized, creating an outward flow that prevents outside particles from seeping in through any crack or gap. It is a fortress against the invisible.
The reason for this obsession with cleanliness operates on two levels. The first is practical: dust and molecular contamination degrade the telescope's ability to see. A fingerprint smudged on eyeglasses makes vision blurry; the same principle applies to a space telescope, except the stakes are incomparably higher. Scientists once thought they had detected gravitational waves in 2014, only to discover the signal was dust on the detector. The embarrassment was real. The second reason is philosophical. As humanity sends more spacecraft into orbit and beyond, the question of planetary protection becomes urgent. If a rover lands on Mars carrying Earth microbes, how will scientists ever know whether they have discovered Martian life or merely contaminated the planet with their own? Tardigrades—microscopic creatures that can survive in the vacuum of space—theoretically could hitch a ride on a spacecraft. The possibility, however remote, demands vigilance.
For the Webb, the stakes are somewhat lower. The telescope will remain in the vacuum of space, not landing on any world. Lepage is skeptical that Earth organisms could survive the journey and then somehow seed another planet. But the principle remains: humanity's reach into the cosmos should not be a vector for Earth's biological material. The cleanroom protocols exist to honor that principle.
The telescope's journey was far from over. Its mirrors were assembled in California. Other components were built in Maryland. Everything had to be shipped to French Guiana for launch at the European Spaceport near Kourou. At every stage of transport, every handoff, every moment of exposure, the risk of contamination persisted. Lepage and her team would arrive in French Guiana in September to establish a final cleanroom on-site, a last sanctuary before launch. A final inspection would follow, though Lepage would not be directly involved in that last check.
Hubble, meanwhile, was aging. The telescope that had transformed humanity's understanding of the cosmos was beginning to fail. In June 2021, NASA had suspended its science operations due to a computer issue. Within the next decade, Hubble would likely begin to decay beyond repair. The James Webb was arriving at precisely the moment it was needed most. Lepage believed it would rewrite the astronomy books. But first, it had to survive the journey from Earth—pristine, untouched, and impossibly clean.
Notable Quotes
A good example is if you wear glasses and smudge your finger on the lens—oil from your finger gets on it and you can't see very well.— Colette Lepage, contamination control engineer
It will rewrite astronomy books.— Colette Lepage, on the James Webb's potential
The Hearth Conversation Another angle on the story
Why does a single speck of dust matter so much? Isn't the telescope built to withstand the environment of space?
The telescope is built to see incredibly faint light from the edge of the universe. A particle of dust on the mirror scatters that light, like a smudge on your glasses. In space, you can't just wipe it clean.
But couldn't they design it to be more resilient to contamination?
They could, but it would compromise the science. The Webb needs to be as sensitive as possible. That sensitivity is what makes it vulnerable. It's a trade-off.
You mentioned planetary protection—the idea of not contaminating Mars. How seriously do scientists take that risk?
Seriously enough that it's written into international law. But for the Webb, it's less about Mars and more about the principle. We're sending human artifacts into the cosmos. We should do it cleanly.
What's the hardest part of your job?
Keeping people focused on something they can't see. A speck of dust is invisible. The risk is abstract. But the cost of failure is concrete—nine billion dollars and a decade of work.
Have you ever had a close call?
There are always close calls. A hair falls. Someone's glove tears. You catch it, you fix it, you move on. The system is designed to catch mistakes before they become disasters.
What happens after launch?
I watch from Earth. If contamination has compromised the telescope, we'll know within weeks. If it hasn't, the Webb will begin seeing things we've never seen before. Either way, my part is done.