Editorial Team - SATNow
The NEOWISE spacecraft, initially launched in 2009 with funding from NASA’s Planetary Science Division, began as the Wide-field Infrared Survey Explorer (WISE). This mission aimed to survey the entire sky in infrared light, capturing images of distant galaxies, cooler red dwarf stars, exploding white dwarfs, outgassing comets, and near-Earth objects (NEOs). Using four infrared wavelengths (3.4, 4.6, 12, and 22 μm), WISE observed the full sky until it ran out of frozen hydrogen coolant in September 2010.
NASA reactivated and renamed the mission NEOWISE in 2013, directing it to focus on finding and studying NEOs—asteroids and comets that come near Earth’s orbit and might pose a threat. NEOWISE’s infrared capabilities allow it to detect the heat from these objects, making it especially useful for spotting dark, faint NEOs that optical telescopes could miss. This ongoing mission has created a valuable archive of data on solar system objects.
Historical Background and Mission Evolution
NASA launched the WISE (Wide-field Infrared Survey Explorer) spacecraft into near-Earth orbit on December 14, 2009, as an infrared space telescope.
WISE surveyed the entire sky in four infrared bands (3.4, 4.6, 12, and 22 μm) until its frozen hydrogen coolant was used up in September 2010. During its mission, WISE made remarkable discoveries: it found the universe's most luminous galaxy, which shines with the power of 300 trillion suns, challenged theories about a hidden "Planet X" in the far reaches of our solar system, uncovered millions of hidden black holes, and detected elusive brown dwarfs—cold objects that are neither stars nor planets. It even identified Y dwarfs, the coldest class of star-like objects, with temperatures similar to a human body. WISE cataloged over 750 million objects through two full-sky scans, mapping the universe around Earth.
However, as the coolant ran out, the telescope began to warm up, reaching temperatures as high as -334°F (-203°C), which started to interfere with its ability to detect faint objects billions of light-years away.
The spacecraft went into hibernation in February 2011 after completing its primary mission. In late 2013, NASA’s Planetary Science Division reactivated WISE, renaming it NEOWISE, to focus on identifying and characterizing near-Earth objects (NEOs). NEOs are asteroids and comets that approach Earth's orbit and may pose a threat.
The mission resumed in December 2013, and within six days, NEOWISE had already discovered its first potentially hazardous near-Earth asteroid.
Mission Objective
The NEOWISE project is the asteroid-tracking phase of the Wide-field Infrared Survey Explorer (WISE) mission. Managed by NASA's Science Mission Directorate through the Jet Propulsion Laboratory (JPL), NEOWISE is operated with mission support from the Space Dynamics Laboratory at Utah State University, which provided the science instruments, and Ball Aerospace, which built the spacecraft. Science data is processed and archived by IPAC at the California Institute of Technology.
NEOWISE shifted its mission focus from WISE's original astronomical goals to concentrate on identifying and studying near-Earth objects (NEOs), a move that reflects NASA's growing focus on planetary defense. The main objective is now to detect and understand NEOs that could potentially threaten Earth, emphasizing NASA's dedication to monitoring and preparing for asteroid threats.
More than just spotting asteroids, NEOWISE works to detail their characteristics, measuring aspects like size, shape, rotation, and surface makeup. These data help scientists understand individual NEOs and the broader asteroid population in our solar system, making NEOWISE essential for planetary defense strategy.
NEOWISE is also a key player in NASA's larger asteroid detection network, scanning the sky in infrared to complement optical telescopes and other space-based resources. Its infrared capabilities allow it to find dark asteroids that might be overlooked by optical telescopes, enhancing overall detection reliability.
The long-term goal of NEOWISE is to build a complete catalog of near-Earth object properties, supporting both immediate planetary defense efforts and long-term scientific studies. By improving our knowledge of asteroid population trends, NEOWISE also contributes valuable insights into the evolution of our solar system.
Key Dates
NEOWISE, originally WISE, is launched
Technical Specification
The NEOWISE spacecraft's design represents a masterpiece of engineering, carefully balanced to meet its demanding mission requirements. At its core is a 40-centimeter (15.7-inch) aperture telescope, housed within a spacecraft body that measures approximately 2.85 meters in height and 2 meters in diameter. The complete assembly weighs 661 kilograms (1,457 pounds), making it a relatively compact but highly capable space observatory.
The spacecraft's power system is built around solar arrays that generate approximately 551 watts of power. These arrays are designed to maintain optimal power generation despite the spacecraft's continuous rotation and changing orbital position. The power system includes redundant batteries and power distribution units to ensure reliable operation even during periods when the spacecraft passes through Earth's shadow.
NEOWISE operates in a 525-kilometer polar orbit, carefully chosen to maximize sky coverage while maintaining thermal stability. This orbit allows the spacecraft to complete a scan of the entire sky every six months, as it rotates perpendicular to its direction of travel. The orbital parameters are also optimized to minimize the interference from Earth's atmosphere and magnetic field.
The spacecraft's data handling and communication systems are equally sophisticated. A 72-gigabyte solid-state recorder stores observational data until it can be transmitted to Earth via an S-band transmitter. The communication system is capable of downloading approximately 100 gigabits of science data per day, ensuring that no valuable observations are lost due to data storage limitations.
Instruments Used
At the core of NEOWISE’s observational power is a highly advanced infrared telescope system. This 40-centimeter telescope uses a beam splitter and refractive optics to direct incoming light to four infrared detector arrays. Initially, these detectors were cooled to 12 Kelvin through a two-stage cryogenic system, enabling high sensitivity across four infrared bands.
The detector arrays were specifically designed for distinct wavelength bands—3.4, 4.6, 12, and 22 micrometers. When the solid hydrogen coolant was depleted, only the 3.4 and 4.6-micrometer channels could continue functioning using passive cooling. Each array features 1024 x 1024 pixels, capturing high-resolution images of the sky.
The telescope also includes a scan mirror mechanism that stabilizes pointing during observations, offsetting spacecraft movement for sharper images. This setup is protected by a sunshade and thermal blankets to help keep instruments at optimal temperatures.
An advanced electronic control system coordinates the detector arrays, processes raw data, and prepares it for transmission to Earth. With built-in redundancies, the system ensures reliable operation over NEOWISE's extended mission. Additionally, it manages the spacecraft’s orientation and scanning path, allowing for thorough sky coverage.
Major Milestones of NEOWISE
Scientific Capabilities
NEOWISE’s capabilities go well beyond simply spotting asteroids. Its infrared technology detects the heat emitted by celestial objects, allowing it to find dark asteroids that optical telescopes might miss. This feature is essential for tracking near-Earth objects, as many asteroids have very low albedo (reflectivity), making them difficult to spot through traditional methods.
Even with only two infrared channels still operational, NEOWISE’s multi-wavelength observations reveal important details about asteroids. By measuring infrared light at different wavelengths, scientists can estimate an asteroid's size, surface composition, and thermal characteristics. These insights are critical for assessing potential impact risks and understanding the nature of ancient solar system bodies.
NEOWISE scans the sky every 11 seconds, capturing new observations quickly and enabling it to detect moving objects and variations in brightness that reveal details about an asteroid's rotation and shape. Its ability to complete a full sky survey every six months provides frequent updates on known objects and a chance to discover new ones.
NEOWISE’s precision makes it stand out among survey instruments. Its infrared observations allow scientists to determine an asteroid's size independently of its reflectivity, resolving a long-standing challenge in asteroid studies. This accuracy has led to the most reliable measurements of near-Earth asteroid sizes, a crucial asset for planetary defense efforts.
Impact on Planetary Defense
NEOWISE's contributions to planetary defense begin with its role as an early warning system for potentially hazardous asteroids (PHAs). The spacecraft's continuous sky surveillance provides crucial lead time for detecting objects that might pose a risk to Earth. Its ability to detect asteroids well before they come near Earth allows scientists to calculate precise orbital trajectories and assess potential impact risks years or even decades in advance. This early detection capability is fundamental to any potential asteroid deflection strategy.
The accuracy of NEOWISE's measurements has revolutionized our understanding of asteroid impact risks. By providing precise size measurements through infrared observations, the spacecraft helps eliminate uncertainties in asteroid size estimates that can occur with visible-light observations alone. This accurate sizing is crucial for risk assessment, as an asteroid's potential impact energy is directly related to its size and composition. The comprehensive database of asteroid properties compiled by NEOWISE has become an invaluable resource for planetary defense planning.
The mission's data processing pipeline represents a remarkable achievement in real-time threat assessment. Each day, NEOWISE generates approximately 7,500 images, which are rapidly processed and analyzed for moving objects. This massive data stream is handled through sophisticated automated systems that can quickly identify potential threats and alert astronomers for follow-up observations. The speed and efficiency of this process ensure that no potentially hazardous objects are overlooked while minimizing false alarms that could drain valuable observational resources.
The integration of NEOWISE data into global planetary defense strategies has strengthened international cooperation in asteroid monitoring and threat assessment. The spacecraft's observations complement ground-based telescope networks and other space-based assets, creating a robust global detection system. This integrated approach has improved our ability to assess impact probabilities and develop response strategies for potential threats, making Earth's planetary defense capabilities more comprehensive and reliable than ever before.
Scientific Contributions
Beyond its primary mission of asteroid detection, NEOWISE has made fundamental contributions to our understanding of brown dwarfs and failed stars. The spacecraft's infrared observations have revealed numerous previously unknown brown dwarfs, helping scientists understand the distribution and properties of these enigmatic objects. These discoveries have bridged the gap in our understanding between stars and planets, providing crucial data about objects that are too cool to detect with conventional telescopes.
The mission's comprehensive sky surveys have revolutionized our understanding of star formation processes. NEOWISE's infrared observations penetrate dust clouds that obscure visible light, revealing young stellar objects and proto-planetary systems in unprecedented detail. This ability to peer through cosmic dust has allowed scientists to study star-forming regions across the galaxy, providing new insights into how stars and planetary systems evolve from cold molecular clouds.
In the field of galactic astronomy, NEOWISE data has contributed to mapping the structure and evolution of the Milky Way. The spacecraft's infrared observations have revealed previously unknown features in our galaxy's spiral arms and helped identify new star clusters and associations. These discoveries have improved our understanding of galactic dynamics and the distribution of matter throughout the Milky Way, contributing to models of galactic evolution.
The mission's impact on extragalactic astronomy has been equally significant. NEOWISE observations have helped identify and characterize distant galaxies, particularly those obscured by dust that are difficult to study in visible light. The spacecraft's data has contributed to studies of galaxy formation and evolution, providing insights into the cosmic history of star formation and the growth of galactic structures throughout the universe.
Major Achievements
NEOWISE's accomplishments in asteroid detection and characterization have far exceeded initial expectations. The mission has discovered over 300 new near-Earth objects, ranging from small asteroids to potentially hazardous objects large enough to warrant careful monitoring. Each discovery has contributed to our understanding of the population of objects that could potentially impact Earth.
The mission's contributions to asteroid characterization have been equally impressive. NEOWISE has provided detailed measurements for more than 200,000 asteroids throughout the solar system. This includes information about their sizes, compositions, and orbital characteristics. The mission has been particularly effective at characterizing dark asteroids that are difficult to study with optical telescopes.
NEOWISE has made more than 1.5 million infrared measurements of 43,926 different solar system objects, including 1,571 near-Earth objects and 282 comets, and has completed 45% of the scanning for its 21st full-sky map of the universe around us.
Among its many accomplishments after its reactivation, NEOWISE also discovered Comet NEOWISE, which was named after the mission and dazzled observers worldwide in 2020.
One of NEOWISE's most significant achievements was its contribution to the discovery of the first known Earth Trojan asteroid. This finding helped validate theoretical predictions about the stability of asteroid orbits near Earth's orbital path. The discovery has implications for our understanding of solar system dynamics and the potential locations where asteroids might accumulate.
The creation of a comprehensive infrared database of asteroid observations represents another major achievement. This database, containing millions of measurements, serves as a valuable resource for both current research and future planetary defense planning. The data has enabled numerous scientific studies and helped improve our models of asteroid behavior and evolution.
Current Status & Future Of NEOWISE
NEOWISE completed its survey observations on July 31, 2024, and was officially decommissioned on August 8, 2024. Over 10.6 years, NEOWISE conducted 21.3 complete sky surveys, making nearly 1.6 million infrared measurements of over 44,000 solar system objects, including 1,598 near-Earth objects (NEOs) and 291 comets.
NEOWISE provided NASA’s Planetary Data System with a catalog detailing asteroid characteristics, using fits based on initial data processing. The mission also reprocessed all primary mission data to extend its search to fainter objects and improved its photometric and astrometric accuracy. These observations were submitted to the Minor Planet Center for publishing. The physical property catalog will be updated post-mission to include all detected objects and reprocessed data, as well as manual pre-covery searches and stacked observation fits.
NEO Surveyor
NEOWISE’s successor, the NEO Surveyor, is slated for a 2028 launch and will build upon the mission’s groundbreaking work. Originally designed as a brief infrared survey, NEOWISE became one of astronomy’s most valuable assets for monitoring potentially hazardous near-Earth objects. Its extensive asteroid and comet discoveries have strengthened planetary defense efforts and enhanced our knowledge of the solar system’s smaller bodies. NEOWISE has underscored the importance of infrared astronomy in planetary defense, laying a solid foundation for future missions.
The mission’s achievements and adaptability showcase NASA’s ability to optimize space assets, transforming NEOWISE into a long-standing planetary defense tool. Its legacy will shape future space exploration and planetary defense strategies, proving that innovation and adaptability can allow missions to surpass their initial goals and deliver significant scientific insights.
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