The sun that made asteroids glow is now bringing the spacecraft home
For nearly fifteen years, a small spacecraft kept vigil over the dark spaces between worlds, cataloguing the ancient wanderers that share our solar neighborhood. On August 8th, 2024, NASA sent a final command to NEOWISE, closing a mission that began as one thing and became something greater — a sentinel repurposed from cosmic cartographer to planetary guardian. In its long watch, it found more than 3,000 near-Earth objects and gifted the world a comet visible to the naked eye, before the sun itself — through the slow physics of atmospheric drag — drew it back toward the Earth it had so long protected.
- A spacecraft that should have died in 2010 when its coolant ran out instead lived on for eleven more years, hunting the very asteroids that could one day threaten Earth.
- NEOWISE's final image — its 26,886,704th exposure — was captured just before 3 a.m. on August 1st, a quiet last act before engineers silenced its transmitter forever.
- Rising solar activity expanded Earth's atmosphere, wrapping the aging probe in invisible friction it had no fuel left to fight, making its end a matter of physics, not failure.
- The mission's 3,000-plus discoveries and 25 comets have seeded the knowledge base for NEO Surveyor, the next planetary defense spacecraft set to launch in 2027.
- Before year's end, NEOWISE will return as light — burning up in the atmosphere of the planet it spent its second life defending.
On August 8th, 2024, NASA engineers sent a final command to NEOWISE, powering down the spacecraft's transmitter and ending one of the agency's most productive asteroid-hunting missions. The ending, however, was never the whole story.
The spacecraft launched in December 2009 under a different name and a different purpose — WISE, the Wide-field Infrared Survey Explorer, built to map the infrared sky with extraordinary sensitivity. It did so for seven months before running out of the coolant that kept its instruments functional. Rather than abandon the probe, NASA placed it in hibernation and brought it back online in 2013 with a new mission: search for asteroids and comets passing near Earth. The spacecraft's infrared vision was still well-suited to the task, since objects close to the sun glow in those wavelengths.
What followed was eleven years of prolific discovery. NEOWISE identified more than 3,000 near-Earth objects, 215 of them previously unknown, and spotted 25 comets — including the one that would carry its name into public memory. Comet NEOWISE lit up the summer skies of 2020, offering a rare naked-eye spectacle to stargazers around the world. NASA officials called the mission an extraordinary success, crediting it with both expanding scientific knowledge and strengthening the foundation of planetary defense.
The sun ultimately determined the mission's end. Heightened solar activity caused Earth's upper atmosphere to expand, increasing drag on the spacecraft. With no fuel remaining to correct its orbit, NEOWISE took its final image on August 1st — the Fornax constellation, captured in the small hours of the morning — and fell silent a week later. Before the year is out, it will burn up on reentry, a last, luminous passage through the skies it spent so long watching over.
On Thursday, August 8th, NASA engineers sent a final command across the void to a spacecraft that had spent nearly fifteen years watching the sky. NEOWISE, the Near-Earth Object Wide-field Infrared Survey Explorer, powered down its transmitter for the last time, ending one of the agency's most productive asteroid-hunting missions.
The spacecraft's journey began in December 2009, though not as NEOWISE. It launched as WISE—the Wide-field Infrared Survey Explorer—with a different purpose entirely: to scan the entire infrared sky with unprecedented sensitivity. For seven months, it did exactly that, mapping the cosmos in wavelengths invisible to human eyes. Then, in the fall of 2010, the mission hit a wall. The probe ran out of coolant, the liquid that had kept its instruments from overheating. Without it, the heat from its own operations began to corrupt the detailed infrared observations it was designed to make. What might have been the end of the story became instead a beginning.
NASA saw potential in the aging spacecraft and gave it a second life. Engineers put WISE into hibernation in February 2011, then brought it back online two years later with a new assignment: hunt for asteroids and comets that pass near Earth. The spacecraft was still capable of detecting these objects because their close proximity to the sun made them glow in infrared. For the next eleven years, NEOWISE did exactly that, becoming one of the most prolific discoverers in planetary defense.
The numbers tell the story of a mission that exceeded expectations. NEOWISE identified more than 3,000 near-Earth objects, 215 of them previously unknown to astronomers. It spotted 25 comets, including the one that would eventually bear its name—Comet NEOWISE, which brightened the summer skies of 2020 and gave amateur astronomers and casual stargazers a rare naked-eye show. Each discovery added to humanity's understanding of the objects that share our cosmic neighborhood, the ones that could one day pose a threat.
Nicola Fox, the associate administrator for NASA's Science Mission Directorate, called the mission "an extraordinary success story" that helped the agency understand humanity's place in the universe. Laurie Leshin, director of the Jet Propulsion Laboratory that managed the spacecraft, noted that NEOWISE's discoveries had "expanded our knowledge of asteroids and comets, while also boosting our nation's planetary defense." The work mattered not just for what it found, but for what it proved possible—laying the groundwork for the next generation of planetary defense instruments, including the NEO Surveyor spacecraft scheduled to launch in 2027.
But the sun itself sealed NEOWISE's fate. In recent months, increased solar activity heated Earth's upper atmosphere, causing it to expand. That expansion meant more drag on the spacecraft, a slow but relentless pull downward. Unlike some satellites, NEOWISE has no fuel left to boost its orbit and fight back against gravity's patient insistence. The spacecraft took its final image on August 1st, just before 3 a.m. Eastern time—the 26,886,704th exposure of its career, showing part of the Fornax constellation in the Southern Hemisphere. By the end of the year, NEOWISE will burn up in Earth's atmosphere, its long watch finally over.
Notable Quotes
The NEOWISE mission has been an extraordinary success story as it helped us better understand our place in the universe by tracking asteroids and comets that could be hazardous for us on Earth.— Nicola Fox, NASA Science Mission Directorate
Its huge number of discoveries have expanded our knowledge of asteroids and comets, while also boosting our nation's planetary defense.— Laurie Leshin, NASA Jet Propulsion Laboratory
The Hearth Conversation Another angle on the story
Why does it matter that we're losing this particular spacecraft? Aren't there other ways to track asteroids?
NEOWISE was doing something specific—using infrared to see objects that are heated by the sun. That's a particular kind of vision. Yes, there are other telescopes, but this one had been at it for eleven years. It had built up a catalog, a record. You lose institutional knowledge when you lose a tool like that.
The article mentions it was originally designed for something else entirely. How does a spacecraft meant to map the cosmos end up hunting asteroids?
It ran out of coolant. That would have been the end. But someone at NASA looked at what it could still do and saw a second mission in it. That's not waste—that's resourcefulness. Fifteen years of operation from a probe that was supposed to die in 2010.
What does "planetary defense" actually mean in this context?
It means knowing what's out there. If an asteroid is going to come close to Earth, you need to know it exists, know its size, know its trajectory. NEOWISE found 3,000 near-Earth objects. Most won't threaten us. But some might. You can't defend against what you don't see.
The sun's activity is what's killing it now. Is that ironic?
It's the way of things. The sun heats the upper atmosphere, the atmosphere expands, the spacecraft gets pulled down. The same sun that made asteroids glow bright enough for NEOWISE to see them is now bringing the spacecraft home. There's a kind of poetry in that, if you want to see it that way.
What happens to all the data it collected?
It stays. The discoveries don't disappear. The catalog remains. And the next spacecraft—NEO Surveyor in 2027—will build on what NEOWISE learned. The mission ends, but the work continues.