On a clear night, if you look up you can see Starlink satellites streaming across the sky. With the help of binoculars or a telescope you can see other satellites too, as they orbit our little pale blue dot.
But amidst all of those satellites lies a veritable junkyard of space debris that is growing by the year. With over 9,000 metric tons of debris currently in orbit, this growing problem threatens operational spacecraft and the sustainability of space exploration.
Over 300 million pieces of junk
With upwards of 40,000 objects larger than 10 cm are in orbit, and around 30,000 actively tracked by space agencies, smaller debris is far more numerous: an estimated 1 million objects range from 1 to 10 cm, and 330 million are larger than 1 mm. Most of this material is in low Earth orbit (LEO) where satellites like the slowly failing International Space Station (ISS) and mega-constellations such as SpaceX’s Starlink operate, below 2,000 km altitude.
The debris originates, in large part, from decades of space missions, including spent rocket stages, decommissioned satellites, and fragments from collisions or explosions, such as a 2007 Chinese anti-satellite test that generated over 3,000 trackable pieces.
These objects travel at speeds up to 10 km/s—10 times faster than a bullet—making even small fragments capable of causing significant damage to other spacecraft and a lethal threat to astronauts during space walks.
Risks to Satellites
So how risky is this? Well, sub-millimeter particles regularly impact satellites, causing minor surface erosion but rarely critical damage. Millimeter-sized debris (1–10 cm) poses a greater threat, as these objects are too small to track yet large enough to penetrate spacecraft shielding. Larger debris (>10 cm) is tracked by systems like the U.S. Space Surveillance Network, which monitors about 20,000 objects to enable collision avoidance maneuvers.
The International Space Station, for example, performed 29 debris-avoidance maneuvers between 1999 and 2021, while Starlink satellites executed over 25,000 maneuvers from December 2022 to May 2023 to avoid tracked debris.
The Kessler Syndrome
The Kessler Syndrome is a theoretical scenario where the collision of larger items of junk generate more debris, triggering a sizeable wave that could render LEO unusable for decades. This is one of our space agencies’ greatest fears. With over 5,000 satellites launched since 2019, primarily for mega-constellations (like Starlink), the risk of such an event is increasing. Without action, the Kessler Syndrome could become a reality within 5–20 years, rendering LEO off-limits for everybody.
Efforts to Mitigate Space Debris
So how can we avoid making a mess of our upper atmosphere and near-earth orbit? The junk problem requires prevention, tracking, and active removal. So far, we only appear to be tracking junk, though there are signs that space agencies are beginning to understand they are their own worst enemies.
Modern satellites are designed to deorbit within five years of mission end or relocate to higher “disposal orbits.” Approximately 60–80% of rockets launched in the last decade complied with these standards, with 30% performing controlled reentries since 2017. The United Nations’ Committee on the Peaceful Uses of Outer Space has established international guidelines to encourage similar practices globally.
Advanced tracking systems are critical for collision avoidance. The U.S. Space Surveillance Network uses ground-based radars and optical sensors to monitor objects as small as 3 mm. Australia’s Space Environment Research Centre is developing laser-based tracking to enhance orbit predictions. These systems allow operators to maneuver satellites away from large debris, though smaller objects remain untrackable.
Removing existing debris is a growing focus. The European Space Agency’s ClearSpace-1 mission, planned for 2026, will use a robotic “chaser” satellite to capture a 94 kg PROBA-1 satellite and guide it to burn up in Earth’s atmosphere. Japan has explored technologies like space nets and electrodynamic tethers. The RemoveDEBRIS mission (2018) successfully demonstrated nets, harpoons, and dragsails on dummy targets. Innovative startups like Astroscale are advancing the field of debris removal; its ADRAS-J mission (launched 2024) is currently studying a 2009 rocket stage to plan its removal, while CisLunar Industries is developing methods to recycle debris into materials like metal wire or fuel. Other concepts, such as ground-based lasers or ion beam shepherds, are also under investigation.
Don’t touch my junk!
Given the fractured nature of our geopolitical structures, challenges in addressing space debris persist. Technically, capturing small, fast-moving debris without creating more fragments is unimaginably complex. Economically, cleanup missions are costly, and the financial incentives for private companies remain unclear. Geopolitically, 96% of debris originates from the U.S.,
Russia, and China, but international treaties, such as the 1967 Outer Space Treaty, prohibit removing another nation’s objects without consent. New treaties are being proposed to facilitate cooperative cleanup.
In 2023, the U.S. Senate introduced a bill to incentivize debris removal and recycling. The U.S.
Federal Communications Commission also fined Dish Network in 2023 for improper satellite disposal, signaling stricter enforcement is on its way. However, environmental concerns persist, as reentering debris (approximately three large objects daily) releases aluminum oxide, potentially harming Earth’s ozone layer.
Clear skies
The space debris problem threatens the long-term sustainability of space missions. So what can be done? From improved satellite designs to cutting-edge removal technologies like wooden satellites (planned by Japan and NASA for 2025 to reduce persistent debris), innovation is driving progress. International cooperation, robust regulations, and industry engagement are essential in preventing Kessler Syndrome becoming more than a theory and ensuring space remains accessible. By addressing this challenge, humanity can preserve the orbital environment for future generations of explorers and innovators, or as we are now seeing, a space weapon race utilizing laser technology to combat ICBMs. Golden Dome anyone?