What is the International Asteroid Warning Network, and Why is It Important?

Guarding Earth from Cosmic Threats

The solar system is a dynamic and busy place, filled with rocky and icy remnants from its formation billions of years ago. The Earth travels through this environment, which includes countless asteroids and comets. While the vast majority of these objects pose no threat, a small fraction are classified as Near-Earth Objects (NEOs), whose orbits bring them into Earth’s neighborhood. The potential hazard from these objects is not theoretical. It’s a low-probability but high-consequence natural disaster.

In response to this global challenge, the international community established the International Asteroid Warning Network (IAWN). The IAWN isn’t a single, physical entity or organization. It’s a framework for communication, coordination, and cooperation. It connects the world’s observatories, space agencies, and data centers, ensuring that when a potentially hazardous object is detected, the information is shared quickly, verified accurately, and communicated to the world’s governments and public with a single, clear voice. This article explores the structure of the IAWN, its history, its operational procedures, and the broader field of planetary defense it supports.

The Dawn of Planetary Defense

For most of human history, the idea of a threat from the sky was relegated to mythology or, later, science fiction. The scientific community itself was long skeptical that celestial impacts had played a significant role in Earth’s history. This view began to change dramatically in the late 20th century. Geologists and physicists uncovered mounting evidence that a massive impact 66 million years ago was responsible for the Cretaceous–Paleogene extinction event that wiped out the dinosaurs. The “impossible” had, in fact, happened.

A more immediate and visceral wake-up call came in 1994. Astronomers watched as fragments of Comet Shoemaker-Levy 9 slammed into the planet Jupiter. The impacts created dark scars in the gas giant’s atmosphere, some larger than the Earth itself. It was the first time humanity had ever witnessed such a large-scale collision in real-time. What had happened to Jupiter could, clearly, happen to Earth.

This realization spurred the first organized efforts to find and catalog NEOs. Surveys, primarily funded by the United States Congress and operated by NASA, began to scan the skies. These early efforts, like the Spacewatch project at the University of Arizona, proved that the inner solar system was populated with many more NEOs than previously thought.

The final catalyst for a truly coordinated global response came not from a distant planet, but from the skies above a Russian city. On February 15, 2013, an asteroid approximately 20 meters (66 feet) wide entered Earth’s atmosphere over the region of Chelyabinsk. It was traveling at over 19 kilometers per second (42,500 mph). The object was too small to have been detected by the surveys of the time, and it approached from the direction of the Sun, a well-known blind spot for ground-based telescopes.

The asteroid exploded in a massive air burst about 30 kilometers (18 miles) above the ground. The resulting shockwave released energy equivalent to hundreds of kilotons of TNT, shattering glass across six cities and injuring over 1,500 people, mostly from flying debris. The Chelyabinsk meteor was a stark reminder that even small, undetected asteroids could cause significant localized damage and civil disruption. It proved that the asteroid threat wasn’t just a global, extinction-level problem; it was also a regional, near-term hazard.

The event galvanized the international community. Later that same year, the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) formally adopted recommendations for an international response to the NEO threat. From these recommendations, two key bodies were established: the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG).

What is the International Asteroid Warning Network (IAWN)?

The IAWN was officially established in 2014. Its core function is to serve as the global hub for information sharing and warning. It is a partnership of institutions, agencies, and observatories that contribute to the detection, tracking, and characterization of potentially hazardous objects.

The network operates on a set of core principles:

1. Open Data Sharing: All IAWN partners agree to share their NEO observations, data, and analyses promptly.
2. Verification: The network provides a mechanism for experts to cross-check and validate findings. This prevents the dissemination of false alarms or inaccurate information.
3. Unified Communication: IAWN’s purpose is to formulate a single, clear, and unambiguous message about any credible threat. It coordinates this messaging among space agencies and governments.
4. Public Awareness: It serves as an authoritative source of information for the public and the media, helping to separate fact from speculation.

IAWN is not a new bureaucracy. It doesn’t own any telescopes or satellites. Instead, it leverages the existing and future capabilities of its members. Its members include major space agencies like NASA, the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), and the China National Space Administration (CNSA), as well as national agencies, university-run observatories, and data processing centers. The IAWN Steering Committee, composed of representatives from these members, guides the network’s activities and protocols.

The Core Components of IAWN

The work of planetary defense, coordinated by IAWN, can be broken down into three main phases: finding, tracking, and characterizing.

Finding: The All-Sky Surveys

The foundation of all planetary defense is finding the objects in the first place. This job falls to powerful, wide-field survey telescopes that repeatedly scan the night sky. These telescopes take thousands of images, night after night. Sophisticated software then analyzes these images, looking for tiny points of light that have moved relative to the background stars.

Major “finders” that contribute data to the network include:

• Catalina Sky Survey: Operated by the University of Arizona, this has historically been one of the most prolific NEO-discovery programs.
• Pan-STARRS: A pair of telescopes in Hawaii operated by the University of Hawaii. They survey vast swaths of the sky every night, discovering thousands of new objects, from small asteroids to distant supernovae.
• ATLAS (Asteroid Terrestrial-impact Last Alert System): Also operated by the University of Hawaii with nodes in Chile and South Africa, ATLAS is designed to scan the entire visible sky every 24-48 hours. Its specific design provides a “last alert” for smaller asteroids, like Chelyabinsk, days or weeks before a potential impact.
• NEOWISE: This NASA mission repurposed an orbiting infrared telescope. From its vantage point in space, NEOWISE can detect asteroids that are dark and non-reflective, which are often missed by optical telescopes on the ground. Its infrared sensors detect the heat radiated by the asteroid itself.

Tracking: The Global Clearinghouse

Finding an object once is not enough. To determine its orbit and predict its future path, it must be “tracked” with follow-up observations. This is where the global nature of IAWN is essential.

When a survey like Pan-STARRS detects a new, fast-moving object, it sends the astrometric data (its position in the sky and the time) to one central location: the Minor Planet Center (MPC).

The MPC, sanctioned by the International Astronomical Union (IAU) and hosted at the Center for Astrophysics | Harvard & Smithsonian, is the world’s official clearinghouse for all observations of small bodies in the solar system. The MPC’s computers collect observations from hundreds of observatories, link them together, and compute a preliminary orbit.

This new object and its rough orbit are then posted to the Near-Earth Object Confirmation Page (NEOCP). This page acts as a global bulletin board, alerting other astronomers (both professional and amateur) around the world. An observatory in Spain might pick it up as the Sun sets in Arizona. As the Earth rotates, astronomers in Australia or Japan can provide more data. Each new observation lengthens the “orbital arc,” allowing for a much more precise orbit calculation.

Characterizing: Knowing the Enemy

Once an object’s orbit is well-known, the next question is: what is it? IAWN coordinates resources to characterize the object. This involves determining its size, shape, composition, and rotation.

• Size: This is the most important factor in determining the potential damage. A 50-meter asteroid can excavate a large crater or cause a powerful air burst, while a 1-kilometer asteroid could cause a global catastrophe. Size is often estimated by an object’s brightness, but this can be misleading. A large, dark asteroid might appear as bright as a small, highly reflective one. This is why infrared telescopes like NEOWISE are so valuable. By measuring the object’s heat, they can determine its size regardless of its reflectivity (or albedo).
• Composition: Is the asteroid a solid piece of iron, a loosely packed “rubble pile” of boulders held together by gravity, or a mix of rock and ice? This affects how it might break up in the atmosphere and how a mitigation mission might interact with it.
• Radar Astronomy: The most powerful characterization tool is radar. Giant radio antennas, like NASA’s Goldstone Deep Space Communications Complex in California, can bounce signals off a passing NEO. The returning echo provides incredibly precise data on the object’s distance and velocity, refining its orbit 100-fold. It can also produce radar images that reveal the asteroid’s shape, whether it has moons, and how fast it’s spinning.

How an Asteroid Threat is Handled: From Detection to Warning

The IAWN provides the formal process for managing a potential threat. This step-by-step procedure ensures that data is vetted and communication is clear.

Step 1: Discovery and Reporting

A survey telescope (e.g., Catalina) detects a new NEO. The data is sent to the Minor Planet Center (MPC).

Step 2: Confirmation and Orbit Calculation

The MPC posts the object to the NEOCP. Observatories worldwide conduct follow-up observations. The MPC collects this data and computes a solid preliminary orbit. Once confirmed, the object receives an official designation (e.g., “2026 GHF”).

Step 3: Initial Impact Risk Assessment

This new, high-precision orbit data is automatically ingested by two independent, autonomous systems:

• Sentry System: Operated by the Jet Propulsion Laboratory (JPL) for NASA.
• NEODyS (Near-Earth Objects Dynamic Site): Operated by SpaceDyS at the University of Pisa with support from ESA.

These systems “propagate” the orbit 100 years into the future, running thousands of simulations that slightly vary the orbital parameters within the margin of error. If any of these “virtual asteroids” hit Earth, the system flags a potential future impact. The object is then placed on a public “risk list.”

Step 4: IAWN Coordination

The vast majority of objects on the risk list (over 99%) are a product of orbital uncertainty. They are based on short “arcs” of just a few days. IAWN’s role is to help eliminate this uncertainty. The IAWN Steering Committee is notified of any object that reaches a certain threshold of concern. The committee then uses its network to coordinate a global observing campaign, prioritizing the new object.

Astronomers are tasked to get more data. Powerful radar assets like Goldstone may be tasked to “ping” the object. This new data rapidly refines the orbit. In almost every case, the refined orbit shows that the object will miss Earth completely, and it is removed from the risk list.

Step 5: The Credible Threat Scenario

What happens if the probability of impact doesn’t go to zero? What if, as more data comes in, the probability gets higher?

This is the scenario IAWN was built for. If an object is confirmed to have a significant impact probability (e.g., greater than 1%) or is very large, IAWN activates its formal warning protocol.

1. Internal Validation: All calculations are double- and triple-checked by multiple IAWN partners (NASA, ESA, etc.). This ensures the data is indisputable.
2. Notification of Governments: IAWN, through its members and in coordination with the UN Office for Outer Space Affairs (UNOOSA), officially notifies national governments.
3. Unified Public Communication: IAWN coordinates the public announcement. The goal is to prevent panic and speculation by providing a single, authoritative source of information. The notification would include the calculated impact time, the “risk corridor” (the potential impact path on Earth’s surface), and the estimated effects (e.g., air burst, ground impact, tsunami risk) based on the object’s characterized size.

This process ensures that by the time a warning is issued, it is based on a global scientific consensus.

Measuring the Hazard: The Torino and Palermo Scales

Communicating risk to the public is notoriously difficult. To standardize this, scientists developed two scales, both of which are used by IAWN.

The Torino Scale

The Torino Scale is the primary tool for communicating risk to the public and media. It’s a simple 0-to-10 color-coded scale that combines the probability of impact with the potential kinetic energy (damage) of the object.

• Level 0 (White): No Hazard. The object has a zero or near-zero chance of impact, or it’s so small it will burn up harmlessly in the atmosphere.
• Level 1 (Green): Normal. A routine discovery. The object merits monitoring, but there’s no public cause for concern. Further observations will almost certainly downgrade it to Level 0.
• Levels 2-4 (Yellow): Meriting Attention. The object’s orbit is not yet fully determined. Observations are underway to refine the risk. These are “concerning” but not “threatening.”
• Levels 5-7 (Orange): Threatening. A credible threat of a close approach with a potential for localized (Level 5) to regional (Level 7) devastation. Such an event would trigger serious contingency planning.
• Levels 8-10 (Red): Certain Collision. A definite impact is predicted. The levels correspond to the scale of damage: Level 8 (localized), Level 9 (regional), and Level 10 (global catastrophe).

To date, no object has ever remained above a Level 1 for long. The asteroid 99942 Apophis famously held a Level 4 designation for a few days in 2004, but subsequent observations have completely ruled out any impact risk for the foreseeable future.

Here is a simplified breakdown of the Torino Scale in a table format.

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The Palermo Technical Impact Hazard Scale

While the Torino Scale is for the public, scientists and engineers use the Palermo Technical Impact Hazard Scale. This is a more complex, logarithmic scale.

It compares the calculated impact risk of a specific object to the “background hazard.” The background hazard is the average, ever-present risk from all other asteroids of a similar size or larger, up to the date of the potential impact.

• A Palermo Scale value of 0 means the object is just as dangerous as the random background hazard.
• A value of -2 means the object is only 1% as dangerous as the background hazard (in other words, not concerning).
• A value of +1 means the object is 10 times more dangerous than the background hazard.

The Palermo Scale is the technical tool used by IAWN experts to prioritize which objects require the most immediate follow-up observations.

The Other Half of the Equation: SMPAG

IAWN’s job is to warn. But what if a warning is issued? What if an impact is confirmed, and there are several years of lead time? This is where the second UN-endorsed body comes in: the Space Mission Planning Advisory Group (SMPAG).

SMPAG (often pronounced “sam-page”) is the forum for the world’s space agencies. Its purpose is to prepare for an actual mitigation mission – a plan to deflect the asteroid. While IAWN is the “warning” network, SMPAG is the “action” planning group.

SMPAG brings agencies like NASA, ESA, Roscosmos, CNSA, and JAXA to the same table. They don’t just discuss how to deflect an asteroid; they discuss the practical, real-world problems:

• Who builds the spacecraft?
• Who provides the launch vehicle?
• Who pays for it?
• What are the legal implications under the Outer Space Treaty?
• What if the deflection attempt fails?

By having these discussions before a threat is found, SMPAG lays the groundwork for a rapid, collaborative international response.

Testing the System: Mitigation and Exercises

The work of IAWN and SMPAG is not just theoretical. The world is actively testing its ability to respond to a threat.

The DART Mission: Humanity’s First Test

On September 26, 2022, humanity conducted its first-ever test of planetary defense. The Double Asteroid Redirection Test (DART) mission, led by NASA and managed by the Johns Hopkins Applied Physics Laboratory (APL), was a spectacular proof of concept.

The target was Dimorphos, a small “moonlet” asteroid orbiting a larger asteroid named Didymos. This binary system posed no threat to Earth, but it was a perfect target. From Earth, astronomers could measure the time it took Dimorphos to orbit Didymos (about 11 hours and 55 minutes) by watching the “eclipses” or regular dips in brightness as one passed in front of the other.

The DART spacecraft, about the size of a vending machine, traveled for 10 months and autonomously slammed into Dimorphos at 14,000 mph. The mission’s goal was to see if this “kinetic impact” could change the moonlet’s orbit.

The results were astonishing. Astronomers had predicted the impact might shorten the orbit by 7 to 10 minutes. Instead, the orbital period was shortened by 32 minutes. The spacecraft didn’t just give the asteroid a simple “push.” The impact blasted tons of rock and debris (known as ejecta) off the asteroid’s surface. This cloud of ejecta streaming into space acted like a thruster, giving the asteroid a massive secondary “recoil” push.

The DART mission, which was observed by telescopes around the world and in space (including a small companion satellite from the Italian Space Agency called LICIACube), proved two things. First, humanity has the technology to intercept a distant asteroid. Second, the kinetic impactor technique works, and it works better than expected.

A follow-up mission from ESA called Hera is now en route to the Didymos-Dimorphos system. When it arrives, it conducts a detailed “crime scene investigation,” studying the impact crater, measuring the mass of Dimorphos, and analyzing the physics of the collision to help refine models for future deflection missions.

Other Mitigation Concepts

The kinetic impactor is the most mature technology, but SMPAG considers others, especially for different types of threats (e.g., larger asteroids, or those with short warning times).

• Gravity Tractor: This is a slow and steady method. A heavy spacecraft would fly alongside the asteroid for months or years. It wouldn’t touch it. Instead, the tiny, mutual gravitational pull between the spacecraft and the asteroid would be enough to gently and predictably tug the asteroid onto a new, safe trajectory.
• Nuclear Standoff Explosion: For a “last resort” scenario – a very large object or one discovered with only months to spare – a nuclear device is the only option with enough energy. The plan would not be to blow the asteroid up (which could create a dangerous “shotgun blast” of fragments). Instead, the device would be detonated at a “standoff” distance near the asteroid. The intense radiation would vaporize one side of the asteroid, creating a massive, rocket-like thrust that would push it off course.

Planetary Defense Exercises

To test the human side of the system, IAWN and NASA’s Planetary Defense Coordination Office (PDCO) regularly conduct hypothetical asteroid threat exercises.

In these exercises, a “virtual” asteroid is “discovered” and given a high probability of hitting Earth in several years. Over the course of months, exercise participants (scientists, engineers, and communications specialists from IAWN member agencies) receive fictional data “injects” that mimic the real flow of information.

They practice the entire process:

1. Coordinating follow-up observations.
2. Characterizing the “threat” (its size, composition).
3. Calculating the impact footprint.
4. Communicating the evolving risk to each other and to the public (via mock press releases).
5. Convening SMPAG to develop and present mitigation options.

These exercises are invaluable. They identify gaps in the system, test international communication protocols, and build the personal relationships and trust needed to manage a real crisis.

Current Capabilities and Future Challenges

The U.S. Congress mandated NASA in 2005 to find 90% of all NEOs that are 140 meters in diameter or larger. An object of this size would not end civilization, but it could wipe a state or small country off the map.

As of today, that goal has not been met. While astronomers have found over 95% of the 1-kilometer “civilization-enders” (and none pose a threat), they have only found an estimated 40-50% of the 140-meter objects. There are thousands still out there, undiscovered.

The challenge is twofold. First, these objects are small and often very dark. Second, ground-based telescopes are blind to objects approaching from the direction of the Sun, as the Chelyabinsk event proved.

To close this gap, a new generation of “finders” is coming online, and their data will be channeled through IAWN.

• Vera C. Rubin Observatory: Currently under construction in Chile, this massive ground-based observatory conducts the Legacy Survey of Space and Time (LSST). It will scan the entire available sky every few nights with unprecedented depth. It’s expected to increase the known population of NEOs by a factor of 10, finding tens of thousands of new objects and providing high-precision tracking for them.
• NEO Surveyor: This is NASA’s next-generation planetary defense mission. It’s a space-based infrared telescope specifically designed to find and track hazardous asteroids. It will be placed at the Sun-Earth L1 Lagrange point, a gravitationally stable spot between the Earth and the Sun. From this vantage point, it can look “outward” from Earth’s orbit and spot the asteroids that ground-based telescopes miss, including those in the “Sun glare” blind spot. NEO Surveyor is the mission designed to finally meet the 140-meter congressional mandate.

Summary

The International Asteroid Warning Network (IAWN) is a model of global cooperation. It formalizes the process of discovery, tracking, characterization, and warning for a natural hazard that affects the entire planet. It is not a single agency but a “network of networks,” connecting the world’s best scientific and technical assets to create a unified system of defense.

IAWN ensures that data is shared, calculations are verified, and communications are clear. It works in lockstep with the Space Mission Planning Advisory Group (SMPAG) to prepare for a mitigation response, should one ever be needed.

Through real-world tests like the DART mission, humanity has moved planetary defense from the realm of science fiction to scientific fact. While the threat from asteroids is real, the ongoing work of IAWN and its global partners demonstrates that it is a solvable problem. The key remains finding all the hazardous objects first. With new assets like the Vera C. Rubin Observatory and NEO Surveyor on the horizon, the network is poised to complete its inventory, standing as a silent, coordinated guardian for the planet.