NASA’s only space telescope solely dedicated to planetary defense, NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer), has shut down its transmitter for the final time, bringing an end to its 15-year career. This spacecraft, initially designed for a seven-month mission to scan the sky for infrared signals, vastly outlived its expected lifespan, making remarkable contributions to our understanding of near-Earth objects.
NEOWISE detected over 200 previously unknown near-Earth objects, including 25 new comets, and gathered a wealth of data on 44,000 other objects traversing our solar system. Its mission, officially concluded on July 31, comes to a close as the sun enters its peak activity period, known as solar maximum. This heightened solar activity poses a threat to the spacecraft’s stability, potentially dragging it into Earth’s atmosphere for a fiery reentry. Lacking propellant to adjust its orbit, NEOWISE has been steadily descending towards Earth for years and is expected to safely burn up in the atmosphere in late 2024.
“This telescope has truly outlived its original lifespan,” Amy Mainzer, a professor at the University of California, Los Angeles, and principal investigator for both NEOWISE and its successor, NEO Surveyor, stated in an interview last year. “We obtained far more from it than we anticipated.”
NEOWISE, originally launched in 2009 as WISE (Wide-field Infrared Survey Explorer), resembled a prototypical version of the James Webb Space Telescope. Its initial mission was to map the entire sky in infrared light, seeking traces of faint and ancient emissions from the early universe. Its exceptional sensitivity, exceeding scientists’ expectations, led NASA to extend its mission under the name NEOWISE until 2011, enabling it to survey the main asteroid belt between Mars and Jupiter.
After exhausting its coolant, crucial for maintaining the spacecraft’s temperature and preserving the sensitivity of its infrared sensors, NEOWISE was put into hibernation. However, subsequent analysis of its collected data revealed its continued ability to detect nearby solar system objects reflecting sunlight. This discovery prompted NASA to revive NEOWISE in 2013 for another decade of surveying near-Earth objects.
Among the numerous objects the telescope identified, its most notable discovery is the bright comet bearing its name: comet C/2020 F3 NEOWISE, which graced Earth’s skies in July 2020.
NEOWISE’s demise creates a temporary gap in Earth’s planetary defense capabilities, as no other NASA space telescope dedicates its full focus to hunting near-Earth objects, some of which could potentially pose a danger to our planet. However, a more powerful infrared telescope, NEO Surveyor, is currently under development, aiming to succeed NEOWISE’s mission with a planned launch date no earlier than 2027.
Upon deployment, NEO Surveyor will conduct a complete scan of the sky every two weeks, as stated by Mainzer. It will also feature a specialized solar shade, allowing it to search for asteroids lurking near the sun’s glare – a region of space considered our greatest planetary defense blind spot.
In the meantime, scientists will rely on robust ground-based observatories to ensure no hazardous near-Earth asteroids go unnoticed. “We will have the ground-based telescopes, and these days they discover the majority of objects anyway,” Mainzer mentioned. “Catalina Sky Survey [in Arizona] and Pan-STARRS [in Hawaii] are the two surveys currently identifying the most objects, and this has been the case for quite some time.”
With the aid of such surveys, astronomers have mapped the orbits of over 34,000 near-Earth asteroids, according to NASA, and none are predicted to pose a threat to Earth for at least the next century.
