The NASA project NEOWISE, which has given astronomers a detailed view of near-Earth objects – some of which could strike the Earth – ended its mission and burned on reentering the atmosphere after over a decade.
On a clear night, the sky is full of bright objects – from stars, large planets and galaxies to tiny asteroids flying near Earth. These asteroids are commonly known as near-Earth objects, and they come in a wide variety of sizes. Some are tens of kilometers across or larger, while others are only tens of meters or smaller.
On occasion, near-Earth objects smash into Earth at a high speed – roughly 10 miles per second (16 kilometers per second) or faster. That’s about 15 times as fast as a rifle’s muzzle speed. An impact at that speed can easily damage the planet’s surface and anything on it.
Impacts from large near-Earth objects are generally rare over a typical human lifetime. But they’re more frequent on a geological timescale of millions to billions of years. The best example may be a 6-mile-wide (10-kilometer-wide) asteroid that crashed into Earth, killed the dinosaurs and created Chicxulub crater about 65 million years ago.
Smaller impacts are very common on Earth, as there are more small near-Earth objects. An international community effort called planetary defense protects humans from these space intruders by cataloging and monitoring as many near-Earth objects as possible, including those closely approaching Earth. Researchers call the near-Earth objects that could collide with the surface potentially hazardous objects.
NASA began its NEOWISE mission in December 2013. This mission’s primary focus was to use the space telescope from the Wide-field Infrared Survey Explorer to closely detect and characterize near-Earth objects such as asteroids and comets.
NEOWISE contributed to planetary defense efforts with its research to catalog near-Earth objects. Over the past decade, it helped planetary defenders like us and our colleagues study near-Earth objects.
NASA/JPL-Caltech
Detecting near-Earth objects
NEOWISE was a game-changing mission, as it revolutionized how to survey near-Earth objects.
The NEOWISE mission continued to use the spacecraft from NASA’s WISE mission, which ran from late 2009 to 2011 and conducted an all-sky infrared survey to detect not only near-Earth objects but also distant objects such as galaxies.
The spacecraft orbited Earth from north to south, passing over the poles, and it was in a Sun-synchronous orbit, where it could see the Sun in the same direction over time. This position allowed it to scan all of the sky efficiently.
The spacecraft could survey astronomical and planetary objects by detecting the signatures they emitted in the mid-infrared range.
Humans’ eyes can sense visible light, which is electromagnetic radiation between 400 and 700 nanometers. When we look at stars in the sky with the naked eye, we see their visible light components.
However, mid-infrared light contains waves between 3 and 30 micrometers and is invisible to human eyes.
When heated, an object stores that heat as thermal energy. Unless the object is thermally insulated, it releases that energy continuously as electromagnetic energy, in the mid-infrared range.
This process, known as thermal emission, happens to near-Earth objects after the Sun heats them up. The smaller an asteroid, the fainter its thermal emission. The NEOWISE spacecraft could sense thermal emissions from near-Earth objects at a high level of sensitivity – meaning it could detect small asteroids.
But asteroids aren’t the only objects that emit heat. The spacecraft’s sensors could pick up heat emissions from other sources too – including the spacecraft itself.
To make sure heat from the spacecraft wasn’t hindering the search, the WISE/NEOWISE spacecraft was designed so that it could actively cool itself using then-state-of-the-art solid hydrogen cryogenic cooling systems.
Operation phases
Since the spacecraft’s equipment needed to be very sensitive to detect faraway objects for WISE, it used solid hydrogen, which is extremely cold, to cool itself down and avoid any noise that could mess with the instruments’ sensitivity. Eventually the coolant ran out, but not until WISE had successfully completed its science goals.
During the cryogenic phase when it was actively cooling itself, the spacecraft operated at a temperature of about -447 degrees Fahrenheit (-266 degrees Celsius), slightly higher than the universe’s temperature, which is about -454 degrees Fahrenheit (-270 degrees Celsius).
The cryogenic phase lasted from 2009 to 2011, until the spacecraft went into hibernation in 2011.
Following the hibernation period, NASA decided to reactivate the WISE spacecraft under the NEOWISE mission, with a more specialized focus on detecting near-Earth objects, which was still feasible even without the cryogenic cooling.
During this reactivation phase, the detectors didn’t need to be quite as sensitive, nor the spacecraft kept as cold as it was during the cryogenic cooling phase, since near-Earth objects are closer than WISE’s faraway targets.
The consequence of losing the active cooling was that two long-wave detectors out of the four on board became so hot that they could no longer function, limiting the craft’s capability.
Nevertheless, NEOWISE used its two operational detectors to continuously monitor both previously and newly detected near-Earth objects in detail.
NEOWISE’s legacy
As of February 2024, NEOWISE had taken more than 1.5 million infrared measurements of about 44,000 different objects in the solar system. These included about 1,600 discoveries of near-Earth objects. NEOWISE also provided detailed size estimates for more than 1,800 near-Earth objects.
Despite the mission’s contributions to science and planetary defense, it was decommissioned in August 2024. The spacecraft eventually started to fall toward Earth’s surface, until it reentered Earth’s atmosphere and burned up on Nov. 1, 2024.
NEOWISE’s contributions to hunting near-Earth objects gave scientists much deeper insights into the asteroids around Earth. It also gave scientists a better idea of what challenges they’ll need to overcome to detect faint objects.
So, did NEOWISE find all the near-Earth objects? The answer is no. Most scientists still believe that there are far more near-Earth objects out there that still need to be identified, particularly smaller ones.
NASA/JPL-Caltech/University of Arizona
To carry on NEOWISE’s legacy, NASA is planning a mission called NEO Surveyor. NEO Surveyor will be a next-generation space telescope that can study small near-Earth asteroids in more detail, mainly to contribute to NASA’s planetary defense efforts. It will identify hundreds of thousands of near-Earth objects that are as small as about 33 feet (10 meters) across. The spacecraft’s launch is scheduled for 2027.
Toshi Hirabayashi is a part of several planetary mission teams with NASA, ESA and JAXA through the Georgia Institute of Technology.
Yaeji Kim does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
This article is republished from The Conversation under a Creative Commons license.
10 Best-Selling Science Fiction Books Worth Reading
Dune
Frank Herbert’s Dune is a classic science fiction novel that follows Paul Atreides after his family takes control of Arrakis, a desert planet whose spice is the most valuable resource in the universe. The story combines political struggle, ecology, religion, and warfare as rival powers contest the planet and Paul is drawn into a conflict that reshapes an interstellar civilization. It remains a foundational space opera known for its worldbuilding and long-running influence on the science fiction genre.
Foundation
Isaac Asimov’s Foundation centers on mathematician Hari Seldon, who uses psychohistory to forecast the collapse of a galactic empire and designs a plan to shorten the coming dark age. The narrative spans generations and focuses on institutions, strategy, and social forces rather than a single hero, making it a defining work of classic science fiction. Its episodic structure highlights how knowledge, politics, and economic pressures shape large-scale history.
Ender’s Game
Orson Scott Card’s Ender’s Game follows Andrew “Ender” Wiggin, a gifted child recruited into a military training program designed to prepare humanity for another alien war. The novel focuses on leadership, psychological pressure, and ethical tradeoffs as Ender is pushed through increasingly high-stakes simulations. Often discussed as military science fiction, it also examines how institutions manage talent, fear, and information under existential threat.
The Hitchhiker’s Guide to the Galaxy
Douglas Adams’s The Hitchhiker’s Guide to the Galaxy begins when Arthur Dent is swept off Earth moments before its destruction and launched into an absurd interstellar journey. Blending comedic science fiction with satire, the book uses space travel and alien societies to lampoon bureaucracy, technology, and human expectations. Beneath the humor, it offers a distinctive take on meaning, randomness, and survival in a vast and indifferent cosmos.
1984
George Orwell’s 1984 portrays a surveillance state where history is rewritten, language is controlled, and personal autonomy is systematically dismantled. The protagonist, Winston Smith, works within the machinery of propaganda while privately resisting its grip, which draws him into escalating danger. Frequently categorized as dystopian fiction with strong science fiction elements, the novel remains a reference point for discussions of authoritarianism, mass monitoring, and engineered reality.
Brave New World
Aldous Huxley’s Brave New World presents a society stabilized through engineered reproduction, social conditioning, and pleasure-based control rather than overt terror. The plot follows characters who begin to question the costs of comfort, predictability, and manufactured happiness, especially when confronted with perspectives that do not fit the system’s design. As a best-known dystopian science fiction book, it raises enduring questions about consumerism, identity, and the boundaries of freedom.
Fahrenheit 451
Ray Bradbury’s Fahrenheit 451 depicts a future where books are outlawed and “firemen” burn them to enforce social conformity. The protagonist, Guy Montag, begins as a loyal enforcer but grows increasingly uneasy as he encounters people who preserve ideas and memory at great personal risk. The novel is often read as dystopian science fiction that addresses censorship, media distraction, and the fragility of informed public life.
The War of the Worlds
H. G. Wells’s The War of the Worlds follows a narrator witnessing an alien invasion of England, as Martian technology overwhelms existing military and social structures. The story emphasizes panic, displacement, and the collapse of assumptions about human dominance, offering an early and influential depiction of extraterrestrial contact as catastrophe. It remains a cornerstone of invasion science fiction and helped set patterns still used in modern alien invasion stories.
Neuromancer
William Gibson’s Neuromancer follows Case, a washed-up hacker hired for a high-risk job that pulls him into corporate intrigue, artificial intelligence, and a sprawling digital underworld. The book helped define cyberpunk, presenting a near-future vision shaped by networks, surveillance, and uneven power between individuals and institutions. Its language and concepts influenced later depictions of cyberspace, hacking culture, and the social impact of advanced computing.
The Martian
Andy Weir’s The Martian focuses on astronaut Mark Watney after a mission accident leaves him stranded on Mars with limited supplies and no immediate rescue plan. The narrative emphasizes problem-solving, engineering improvisation, and the logistical realities of survival in a hostile environment, making it a prominent example of hard science fiction for general readers. Alongside the technical challenges, the story highlights teamwork on Earth as agencies coordinate a difficult recovery effort.
10 Best-Selling Science Fiction Movies to Watch
Interstellar
In a near-future Earth facing ecological collapse, a former pilot is recruited for a high-risk space mission after researchers uncover a potential path to another star system. The story follows a small crew traveling through extreme environments while balancing engineering limits, human endurance, and the emotional cost of leaving family behind. The narrative blends space travel, survival, and speculation about time, gravity, and communication across vast distances in a grounded science fiction film framework.
Blade Runner 2049
Set in a bleak, corporate-dominated future, a replicant “blade runner” working for the police discovers evidence that could destabilize the boundary between humans and engineered life. His investigation turns into a search for hidden history, missing identities, and the ethical consequences of manufactured consciousness. The movie uses a cyberpunk aesthetic to explore artificial intelligence, memory, and state power while building a mystery that connects personal purpose to civilization-scale risk.
Arrival
When multiple alien craft appear around the world, a linguist is brought in to establish communication and interpret an unfamiliar language system. As global pressure escalates, the plot focuses on translating meaning across radically different assumptions about time, intent, and perception. The film treats alien contact as a problem of information, trust, and geopolitical fear rather than a simple battle scenario, making it a standout among best selling science fiction movies centered on first contact.
Inception
A specialist in illicit extraction enters targets’ dreams to steal or implant ideas, using layered environments where time and physics operate differently. The central job requires assembling a team to build a multi-level dream structure that can withstand psychological defenses and internal sabotage. While the movie functions as a heist narrative, it remains firmly within science fiction by treating consciousness as a manipulable system, raising questions about identity, memory integrity, and reality testing.
Edge of Tomorrow
During a war against an alien force, an inexperienced officer becomes trapped in a repeating day that resets after each death. The time loop forces him to learn battlefield tactics through relentless iteration, turning failure into training data. The plot pairs kinetic combat with a structured science fiction premise about causality, adaptation, and the cost of knowledge gained through repetition. It is often discussed as a time-loop benchmark within modern sci-fi movies.
Ex Machina
A young programmer is invited to a secluded research facility to evaluate a humanoid robot designed with advanced machine intelligence. The test becomes a tense psychological study as conversations reveal competing motives among creator, evaluator, and the synthetic subject. The film keeps its focus on language, behavior, and control, using a contained setting to examine artificial intelligence, consent, surveillance, and how people rationalize power when technology can convincingly mirror human emotion.
The Fifth Element
In a flamboyant future shaped by interplanetary travel, a cab driver is pulled into a crisis involving an ancient weapon and a looming cosmic threat. The story mixes action, comedy, and space opera elements while revolving around recovering four elemental artifacts and protecting a mysterious figure tied to humanity’s survival. Its worldbuilding emphasizes megacities, alien diplomacy, and high-tech logistics, making it a durable entry in the canon of popular science fiction film.
Terminator 2: Judgment Day
A boy and his mother are pursued by an advanced liquid-metal assassin, while a reprogrammed cyborg protector attempts to keep them alive. The plot centers on preventing a future dominated by autonomous machines by disrupting the chain of events that leads to mass automation-driven catastrophe. The film combines chase-driven suspense with science fiction themes about AI weaponization, time travel, and moral agency, balancing spectacle with character-driven stakes.
Minority Report
In a future where authorities arrest people before crimes occur, a top police officer becomes a suspect in a predicted murder and goes on the run. The story follows his attempt to challenge the reliability of predictive systems while uncovering institutional incentives to protect the program’s legitimacy. The movie uses near-future technology, biometric surveillance, and data-driven policing as its science fiction core, framing a debate about free will versus statistical determinism.
Total Recall (1990)
A construction worker seeking an artificial vacation memory experiences a mental break that may be either a malfunction or the resurfacing of a suppressed identity. His life quickly becomes a pursuit across Mars involving corporate control, political insurgency, and questions about what is real. The film blends espionage, off-world colonization, and identity instability, using its science fiction premise to keep viewers uncertain about whether events are authentic or engineered perception.
