“While we are sad to see this bold mission end, we are excited about the future scientific discoveries that will form the foundation of the next-generation Planetary Defense Telescope.”

NASA’s productive asteroid-hunting mission is over.

Engineers sent a final command to the agency’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft on Thursday, Aug. 8, telling the probe to turn off its transmitter after about 15 years in low-Earth orbit.

“The NEOWISE mission has been an extraordinary success story as it helps us better understand our place in the universe by tracking asteroids and comets that could be hazardous to us here on Earth,” Nicola Fox, NASA’s associate administrator for the Science Mission Directorate, said in a statement Thursday.

“While we are sad to see this bold mission end, we are excited about the future scientific discoveries that will form the foundation of the next generation of the Planetary Defense Telescope,” he added.

NEOWISE launched in December 2009 with a different name and a different mission. Originally called WISE (Wide-field Infrared Survey Explorer), the probe scanned the entire infrared sky during its seven-month primary mission. NASA officials wrote in the same statement that this was done “with much greater precision than previous surveys.”

In the fall of 2010, WISE’s coolant ran out. As a result, the probe can no longer control the heat generated by its own operations, preventing detailed infrared observations of deep space.

But that wasn’t the death blow for WISE. NASA gave the probe an extended mission called NEOWISE, during which it would study objects in the main asteroid belt between Mars and Jupiter.

NASA put NEOWISE into hibernation mode in February 2011, but reactivated it two years later after determining that the probe could still observe asteroids and comets approaching Earth (and had a strong infrared signal, thanks to solar energy).

NEOWISE conducted this study over the next 11 years, making many discoveries along the way. For example, NASA officials said the mission discovered more than 3,000 near-Earth objects, 215 of which were previously unknown to astronomers. NEOWISE also discovered 25 comets, including Comet NEOWISE (aka C/2020 F3), which put on a show for skygazers in the summer of 2020.

The mission also helped lay the groundwork for its planetary defense successor, the asteroid-hunting NEO Surveyor spacecraft, scheduled for launch in 2027.

“The NEOWISE mission has played a key role in our quest to map the sky and understand the near-Earth environment,” Lori Leshin, director of NASA’s Jet Propulsion Laboratory in Southern California, which manages WISE and NEOWISE, said in the same statement.

“Numerous discoveries have expanded our knowledge of asteroids and comets and strengthened our nation’s planetary defenses,” he said. “As we bid farewell to NEOWISE, we also celebrate the impressive achievements of the team behind it.”

A recent increase in solar activity hastened NEOWISE’s end: Heat from the Sun has expanded Earth’s atmosphere, increasing drag on the spacecraft. NASA officials said in the same statement that it will soon be too low for useful scientific operations. NEOWISE cannot increase its orbit to counteract this downward pressure. The probe is expected to burn up in our skies later this year.