Orbital Debris

Background and Context

The age of orbital debris began with the launch of Sputnik 1, the first artificial satellite, in 1957. Since then, the rate of satellite launches has increased rapidly, and the amount of debris launched into orbit is higher than the amount burning up and reentering the atmosphere. Debris accumulates because many objects remain in orbit for long periods. Atmospheric drag eventually removes debris in low Earth orbit, but objects at higher altitudes can persist for decades or centuries. The recent rise of the commercial space industry and the deployment of large constellations has increased the risk of collisions significantly. Currently, the highest densities of debris are found in Low Earth Orbit (LEO) at altitudes lower than 1000 km, while significant amounts also exist in Medium Earth Orbit (MEO) and Geostationary (GEO) orbit. See more on orbit types here.

Objects in low Earth orbit travel at speeds of 7-8 km/s (about 25,000-28,000 km/h), meaning that collisions between debris objects can occur at relative velocities exceeding 10 km/s and occasionally reaching up to 15 km/s. At these speeds, even microscopic fragments, such as paint flecks or millimetre-sized grains have enough energy to penetrate spacecraft surfaces and thermal protection layers, damage optics, or puncture unprotected fuel lines. For larger fragments, the threat is even more significant. A fragment only about 1 cm across impacting at hypervelocity can damage or destroy a satellite. 1) 2) 3) 4) 5) 6) 7)

As debris populations grow, this risk increasingly affects the reliability and cost of space-based services such as GNSS, telecommunications, and weather monitoring. Debris also poses risks to human spaceflight. The International Space Station (ISS) is often forced to periodically move out of the path of tracked objects, and has carried out more than 40 such debris avoidance manoeuvres since its launch in 1998.

Alongside physical damage, the growing debris population drives rising operational and insurance costs. Incorporating advanced shielding, manoeuvring systems, and post-mission disposal services add to the total cost of a mission, and in 2023, the space insurance industry recorded a record loss of approximately $500 million, causing a significant increase in insurance premiums. 8) 9) 10) 11)

The Kessler Syndrome

The worst-case scenario is known as the Kessler Syndrome, a theoretical model introduced in 1978 which describes a cascade of collisions. In this scenario, the density of objects in LEO becomes so high that each collision generates a cloud of fragments that causes additional, secondary impacts, eventually making entire regions in orbit unusable for hundreds of years. This collapse would result in severe outages of data supply chains for navigation, telecommunications, and weather forecasting. 12) 13)

Scientific models suggest that some regions of low Earth orbit may already be approaching a self-sustaining debris growth regime, sometimes described as the early stages of Kessler Syndrome. The ESA Space Environment Report 2025 found that even if all new launches were stopped, the number of objects in orbit would continue to grow for over 200 years because new debris fragments are created faster than atmospheric decay can remove them.

To illustrate the risk, a team of researchers from Princeton University introduced the CRASH (Collision Realization and Significant Harm) clock, a model-based indicator that estimates the time available to restore control after a major system disruption, such as a solar storm that disables collision-avoidance systems, before a catastrophic impact becomes likely. While the CRASH clock was at 121 days in 2018, the deployment of satellite mega-constellations has reduced it to just 2.8 days as of 2025. Simulations suggested that if satellite operators lose control of satellites for 24 hours, there is a 30% probability of a collision occurring within that time period that would start a decades-long Kessler cascade. 12) 13) 14) 15) 16) 17)

Types of Debris

Orbital debris comprises all non-functional, human-made objects currently in Earth orbit or re-entering the atmosphere, and is categorised by its source and size to accurately assess the risks it poses to operations. It is mainly divided into four sources:

• Non-operational payloads: spacecraft that have reached the end of their mission life or failed early
• Rocket stages: fuel tanks and components used to deliver payloads
• Mission-related objects: items released during flight, such as payload fairings
• Fragmentation debris: fragments resulting from on-orbit explosions or high-velocity collisions. The most dangerous type of debris, as it creates a large amount of difficult to track small debris.

Orbital debris is also categorised by its size, which determines its potential for damage. Larger debris, objects larger than 10 cm, can cause significant damage to other spacecraft, but are able to be tracked by radar facilities, such as the U.S. Space Surveillance Network (SSN), China’s space debris monitoring system, and the Russian Space Surveillance System (RSSS). Medium-sized debris, 1 - 10 cm, is untrackable but has enough kinetic energy to disable a spacecraft, while particles smaller than 1 cm can cause damage to parts, such as by puncturing fuel lines. 2) 3) 4) 7) 18) 19) 20) 73) 74)

Furthermore, while natural meteoroids are also present in orbit, the near-Earth environment is dominated by man-made debris, which is concentrated in the most valuable and high-traffic orbits.

Current Debris Levels

The scale of the orbital debris problem is rising every day with each rocket launch and satellite deployment. As of 2026, debris surveillance networks currently track more than 43,000 objects larger than 10 cm, including approximately 9,300 active payloads and over 2,000 spent rocket stages. Statistical models, such as ESA’s MASTER-8 (Meteoroid And Space debris Terrestrial Environment Reference - 8) model predict an estimated 1.2 million fragments of size between 1 - 10 cm and more than 140 million objects smaller than 1 cm. The total mass of all human-made objects in orbit is more than 15,000 tonnes, with most of that mass concentrated in Low Earth Orbit (LEO). Models suggest that the population of debris larger than 10 cm will double within the next 50 years, and will continue rising even without new satellite launches, due to self-sustaining fragmentation events. 21) 22) 23)

A number of fragmentation events have occurred in the near-Earth environment, significantly increasing the amount of debris present. The 2007 Chinese anti-satellite (ASAT) test on the Fengyun-1C satellite is the worst fragmentation event in history, scattering a total of 2,347 trackable fragments (10cm or larger), while the 2009 accidental collision between Iridium 33 and Cosmos 2251 produced more than 1,800 objects 10 cm or larger. In October 2024, the Intelsat 33e satellite exploded in geostationary orbit following, generating estimated 20,000 fragments; however the cause has not yet been publicly confirmed. In December 2025, a Starlink satellite experienced an anomaly, releasing propellant and hundreds of large objects. Following this event, SpaceX reported performing over 144,000 manoeuvres over a six-month period to avoid debris and other spacecraft. 24) 25) 26) 27) 28) 75)

Effect of Solar Cycle

The lifespan of debris in LEO is affected by orbital decay in the thermosphere, which removes debris through atmospheric drag. The amount of drag on a satellite changes significantly across the 11-year solar cycle. Cycle 25 entered its maximum phase in 2024, and the cycle’s progression can be tracked using NOAA’s Solar Cycle Progression dashboard.

During the solar maximum, the Sun emits more ultraviolet (UV) and X-ray radiation, which heats and expands the thermosphere. This raises higher-density air higher into Earth's orbit, increasing the atmospheric drag. This causes debris, mainly in orbits with an altitude lower than 1,000 km, to decay faster during these periods.

During solar minimum, the atmosphere contracts, and the effect of orbital decay slows down. This has to be taken into account during the spacecraft design phase to ensure regulatory compliance. A satellite launched during a solar minimum might stay in orbit for decades longer than one launched during a solar maximum. If a mission is delayed from a planned launch during a solar maximum into a solar minimum phase, the satellite may fail to deorbit within the required time. During intense solar activity, satellites might need to perform orbital manoeuvres every 2-3 weeks to maintain altitude, compared to only four times per year during typical solar phases. 29) 30) 31) 32) 33) 34) 35)

International Treaties and Regulations

Orbital debris regulation has evolved from initial international legal principles to technical guidelines, mainly dictated by the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS). Early frameworks like the 1967 Outer Space Treaty created the initial base laws by mandating that countries avoid the harmful contamination of space. This was expanded by the 1972 Liability Convention, which made countries accountable for damage caused by space objects. In the late 20th century, the Inter-Agency Space Debris Coordination Committee (IADC) was established to develop space debris mitigation guidelines. 36) 37) 38)

IADC Space Debris Mitigation Guidelines (2025)

The Inter-Agency Space Debris Coordination Committee (IADC) represents 13 space agencies, as shown in Table 1 below. Its Space Debris Mitigation Guidelines, which were initially published in 2002 and updated in 2025, are used as the guidelines for best practices. An important part of the guidelines is the 25-year rule, which says that objects in LEO should be deorbited or moved to a less-valuable orbit within 25 years of their mission's end of life (EOL). The guidelines also recommend passivation, which is the removal of all energy sources, such as leftover fuel and battery charge, to decrease the risk of on-orbit explosions.

The January 2025 IADC report warned that while compliance with mitigation measures in LEO has reached between 80% and 95%, this progress is insufficient to ensure long-term sustainability. The report explains that the population of objects larger than 10 cm is projected to more than double in less than 50 years. Because of this, active debris removal is needed to stabilise the environment. 38)

UN COPUOS Long-Term Sustainability (LTS) Guidelines (2019)

The United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS) adopted the Guidelines for the Long-Term Sustainability of Outer Space Activities in 2019. The document recommends 21 guidelines divided into four topics: policy and regulatory frameworks; safety of space operations; international cooperation; and scientific and technical research and development. The guidelines include the performance of conjunction assessments during all mission phases, sharing operational space weather data, and the implementation of measures to decrease the risks of uncontrolled re-entry. 39) 40) 41)

ISO 24113 (Space Debris Mitigation Standard)

ISO 24113 is the primary international standard for space debris mitigation, translating global guidelines and recommendations into requirements and regulations for the space industry. The standard is designed to ensure sustainability of space by defining protected regions and creating technical requirements to prevent the generation of new debris, including the prevention of accidental break-ups, and the disposal of spacecraft at the end of their mission life to minimise collision and re-entry risks. 42)

ESA Space Debris Mitigation Standard

In October 2022, the European Space Agency (ESA) presented its Zero Debris approach as part of Agenda 2025 and the latest ESA Space Debris Mitigation Standard. The Standard describes an approach for ESA to become debris-neutral by 2030, while implementing the Space Debris Mitigation Guidelines of the UN COPUOS. ESA also requires a calculation of successful disposal probability prior to launch, aiming for a probability of successful disposal higher than 90%. In addition, reliable and affordable active debris removal services are planned to be introduced by 2030. This commitment was demonstrated in 2023 with the Aeolus mission, when ESA successfully performed the first assisted re-entry to steer the satellite towards the ocean, despite Aeolus originally being designed under older standards that did not require this. 43) 44) 45) 46)

Mitigation Methods

Methods Currently in Use

The main mitigation method for current active satellites is Space Situational Awareness (SSA) combined with propulsion manoeuvres. Debris tracking networks, such as the U.S. Space Surveillance Network (SSN), monitor objects in space larger than 10cm to generate data for collision probability calculations. When a high probability of collision is detected, operators perform collision avoidance manoeuvres to adjust the trajectory of their spacecraft. For decommissioning, satellites in Low Earth Orbit (LEO) usually utilise controlled or assisted atmospheric re-entry to burn up, while those in Geostationary Orbit (GEO) are moved into graveyard orbits approximately 300 km above the active orbits. 10) 47) 48) 49) 50)

The International Space Station (ISS) uses the most advanced implementations of available mitigation and protection techniques. Its shielding protects habitable modules and high-pressure tanks from particles up to 1 cm in diameter, while larger, trackable objects are avoided through debris avoidance manoeuvres. The ISS has conducted more than 40 such manoeuvres since its launch. In cases where tracking data is inaccurate or insufficient, shelter-in-place protocols are activated, requiring astronauts to take shelter in their docked spacecraft until the threat passes. 51) 52)

Emerging Methods

Orbital debris mitigation methods are being improved by the use of Artificial Intelligence (AI) and new debris removal techniques. Methods such as ground-based or space-based lasers aim to modify the orbit of untraceable debris by using surface ablation and photon pressure. This generates thrust, lowering the object’s orbit and lifespan. Other techniques include drag sails and capture mechanisms.

Ground- and space-based lasers work by shooting at small debris, causing its surface to heat up and vaporise, which generates a thrust in the opposite direction of the laser. This can gradually lower the object’s orbit until atmospheric drag begins affecting it, causing it to burn in the atmosphere. The difficulty with using lasers is the need to track debris small enough to be affected by them, which is difficult with current technology. ESA’s Izaña-1 (IZN-1) laser ranging station in Tenerife, Spain, is designed to be a testbed for new technologies such as this. The station’s laser currently operates at 150 mW, enough to track satellites fitted with retroreflectors, with a plan to upgrade it to a 50 W laser to allow small debris tracking.

Drag sails are a passive deorbiting technique, designed to be deployed by a spacecraft once it reaches end-of-life (EOL). The deployment of sails increases the area of the satellite, significantly increasing the atmospheric drag affecting the spacecraft and reducing the spacecraft’s time in orbit. A different deorbiting concept is the electromagnetic tether. This was demonstrated in 2016 by JAXA’s Kounotori Integrated Tether Experiment (KITE), which was launched onboard Kounotori-6. After transferring cargo and new batteries to the ISS, the spacecraft was supposed to deploy KITE, a tether with an end-mass designed to knock debris towards an Earth reentry orbit. The experiment was unsuccessful after a mechanical failure of the end-mass holding and releasing mechanism, causing KITE to not deploy. 53) 54) 55) 56) 57) 58) 94)

To increase the recovery rate of dead satellites, startups like ANT61 are developing semi-autonomous robotic systems and transponders, which allows ground teams to monitor and communicate with a satellite even if it loses power. 59)

Systems such as GMV's Autonomous Collision Avoidance System (AUTOCA) use Machine Learning (ML) algorithms trained on historical data to automate the decision-making for avoidance manoeuvres, reducing the manual workload for satellite operators. SpaceX already utilises such systems in its Starlink constellation, where onboard sensors allow satellites to autonomously assess risks and execute avoidance manoeuvres. 60) 61)

Commercial companies are also developing Active Debris Removal (ADR) as a for-profit service. Astroscale's ADRAS-J mission performed the first 15 m approach to a large piece of debris, testing the planned capture point for follow-up missions. The ClearSpace-1 mission, funded by ESA and led by ClearSpace SA, developed a four-armed claw to capture the PROBA-1 satellite and guide it to re-enter the atmosphere. 62) 63) 64) 65)

Furthermore, aerospace companies like Northrop Grumman and Lockheed Martin are also developing new services to aid in orbital debris mitigation. Northrop Grumman’s Mission Extension Vehicles (MEV-1 and MEV-2) have successfully docked with Intelsat communications satellites in GEO using a probe that locks into the target's engine nozzle, replacing the satellite's propulsion and attitude control to extend their operational lives by five years. Lockheed Martin’s In-space Upgrade Satellite System (LINUSS) mission has utilised 12U CubeSats to demonstrate the company's new software-oriented architecture, allowing satellites to change mission parameters while already in orbit, preventing the generation of new debris. 66) 67) 68) 69)

Looking Forward

The long-term sustainability of the near-Earth environment has changed significantly over the last few decades. The global space economy is projected to exceed $1 trillion by 2040, with debris estimated to negatively impact global GDP by approximately 1.95% due to asset loss and service disruptions. The rapid expansion of satellite mega-constellations could also pose a risk geopolitically, where a debris collision could be mistaken as a hostile act, potentially triggering further escalation. The increase in large constellations also presents a threat to astronomy, with simulations suggesting that approximately 40% of images from the Hubble Space Telescope will be blocked by satellites if all currently proposed constellations are launched. 70) 71) 72) 93)

Timeline

• October 4, 1957: The Soviet Union successfully launched Sputnik 1, the first artificial satellite. It weighed 83.6 kg and had an orbital period of 98 minutes. The satellite burned up on reentry into the Earth atmosphere on January 4, 1958. 76) 92)

• June 29, 1961: The U.S. Ablestar upper stage exploded approximately 77 minutes after inserting the Transit 4A spacecraft into its orbit, producing 296 cataloged fragments. This marks the first known on-orbit fragmentation event. 77)
• January 27, 1967: The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space went into effect, establishing state liability for damages caused by the launching of objects into outer space. 78)
• June 1, 1978: Donald J. Kessler and Burton G.Cour-Palais released the paper “Collision frequency of artificial satellites: The creation of a debris belt”, introducing the idea of a cascading collision of orbital debris, disabling all artificial satellites in orbit. The event is now known as the Kessler Syndrome. 79)
• January 24, 1978: Kosmos 954, a Soviet nuclear-powered satellite, underwent uncontrolled reentry over Canada, spreading an estimated one-quarter of the reactor core over Canada’s Northwest Territories in the form of submillimeter particles. The radioactive material contaminated an area of approximately 100,000 km2. 80) 81)
• 1993: The Inter-Agency Space Debris Coordination Committee (IADC) was founded, with NASA, ESA, JAXA, and ROSCOSMOS as founding members. The committee is a technical body for debris research and coordination. 82)
• October 2002: The IADC published the first edition of the Space Debris Mitigation Guidelines, the first international technical standard for debris mitigation. It introduced the 25-year post-mission disposal rule for low Earth orbit (LEO) satellites, as well as protected orbits. 83) 84)
• January 11, 2007: China destroyed its Fengyun-1C satellite with a ballistic kinetic kill vehicle (KKV), producing more than 2000 objects larger than 10 cm identified by the U.S. Space Surveillance Network and an estimated 35,000 fragments between 1 cm and 10 cm in size. This was the largest fragmentation event in history, and fragments from the event are still causing issues for operational spacecraft. 85)
• February 10, 2009: Iridium 33 and Kosmos 2251 collided, marking the first hypervelocity collision of two intact satellites. Iridium 33 was at the time an operational U.S. communications satellite, while Kosmos 2251 was a non-functional Russian communications satellite. The U.S. Space Surveillance Network tracked over 1400 new debris larger than 10 cm generated by the collision. 86)
• June 2019: The United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS) adopted the Guidelines for Long-Term Sustainability of Outer Space Activities. The guidelines provide guidance to ensure the safety of space operations, international cooperation, and scientific and technical research and development. 87)
• February 25, 2020: Northrop Grumman’s Mission Extension Vehicle-1 (MEV-1) completed the first commercial in-orbit docking between two spacecraft, attaching to the Intelsat 901 satellite. MEV-1 has a potential to extend the satellite’s lifespan by up to 15 years by providing additional propellant and attitude control. 91)

• November 15, 2021: Russia conducted a test of a direct-ascent anti-satellite (DA-ASAT) missile that destroyed the Kosmos 1408 satellite, creating more than 1500 pieces of trackable debris. 88)

• July 28, 2023: ESA conducted an assisted reentry of the Aeolus satellite, launched in 2018 for wind-profiling research, using its remaining propellant. Aeolus descended from an altitude of 280 km to 150 km over 6 days, with a final manoeuvre completed after, guiding the satellite to burn over Antarctica. 89) 90)
• October 19, 2024: The Intelsat 33e satellite exploded in its geostationary orbit. 75)

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67) Intelsat, “Intelsat Completes Satellite Life-Extension Mission, Makes Space History”, URL: https://www.intelsat.com/newsroom/intelsat-completes-satellite-life-extension-mission-makes-space-history/

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69) Terran Orbital, “LM LINUSS”, URL: https://terranorbital.com/missions/linuss/

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84) UNOOSA, “20 Years of IADC”, URL: https://www.unoosa.org/pdf/pres/stsc2014/tech-32E.pdf

85) NASA, “The Characteristics and Consequences of the Break-Up of the Fengyun-1C Spacecraft”, URL: https://ntrs.nasa.gov/api/citations/20070007324/downloads/20070007324.pdf

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87) UNOOSA, “Long-Term Sustainability of Outer Space Activities”, URL: https://www.unoosa.org/oosa/en/ourwork/topics/long-term-sustainability-of-outer-space-activities.html

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