Space debris: the nightmare of operational satellites

Space debris orbiting Earth — Image generated to provide a good view of the population of objects in the geosynchronous region (~35,785 km altitude). Low Earth orbit (LEO) refers to the region of space located less than 2,000 km from Earth's surface. It is the area most concentrated with orbital debris.
Image source: NASA ODPO (new window)

Scientific summary

The Astronoo article examines space debris, those orbital fragments from decommissioned satellites, abandoned rocket stages and collisions. More than 36,000 objects larger than ten centimeters are being tracked, traveling at nearly 7.8 km/s. The Kessler syndrome describes the possible runaway of chain collisions, threatening telecommunications, satellite navigation and Earth observation. The solutions considered combine mitigation and remediation, but their effectiveness depends on international cooperation. The article highlights the limitations of current systems and the urgency of global governance of circumterrestrial space.

What makes space debris a growing threat to satellites?

This article is devoted to space debris, those artificial objects in orbit that no longer serve any function. Decommissioned satellites, abandoned rocket stages, fragments from explosions or collisions: their number keeps growing. This phenomenon, long underestimated, has become a major concern for space agencies since the 2000s. But what makes this debris a growing threat to modern satellites? The answer lies first in their speed: at 7.8 km/s in low orbit, a fragment of a few centimeters has the energy of a car traveling at full speed. Then, their dispersion turns each collision into a source of new debris, a process described by the Kessler syndrome. Finally, our dependence on satellites (GPS, telecommunications, meteorology, Earth observation) makes each impact potentially costly. The article explores the origin of this debris, the major events that generated it, the consequences for space missions and the solutions considered, from controlled deorbiting to orbital cleanup missions.

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Origin and nature of space debris

Multiple and well-identified sources

Space debris comes from decommissioned satellites, abandoned rocket stages, fragments from collisions or explosions in orbit. In 2025, more than 68,450 objects larger than 10 cm are tracked by surveillance networks, to which are added approximately 1.5 million fragments between 1 and 10 cm and 230 million millimeter-sized fragments. Their relative speed, which can reach \(v \approx 7.8 \, km/s\), gives these debris formidable kinetic energy upon impact.

Table of major space debris-generating events

The table below lists the main generating events of space debris since the beginning of space activities.

Major space debris-generating events
Event	Year	Altitude	Consequences
Explosion of the Fengyun-1C satellite (Chinese anti-satellite test)	2007	865 km	About 3,500 debris initially catalogued; about 1,900 to 2,000 fragments still tracked in 2025
Collision between Cosmos-2251 (Russia) and Iridium-33 (United States)	2009	790 km	First major collision between two active satellites, generating more than 2,000 catalogued fragments
Explosion of an Ariane 1 rocket stage (V16 mission)	1986	~600 km	Several hundred persistent debris, some still in orbit today
Indian anti-satellite test (Mission Shakti, Microsat-R)	2019	300 km	Creation of about 400 debris, critical for the International Space Station (ISS)
Deliberate destruction of the USA-193 satellite (Operation Burnt Frost)	2008	247 km	Debris quickly fell back, but controversy over the militarization of space
Explosion of Pegasus-2 (American rocket stage)	1996	580 km	One of the first major events, with fragments still in circulation
Fragmentation of the Russian satellite Cosmos-1275	1981	975 km	First documented case of spontaneous breakup (defective battery), more than 310 debris
Destruction of the Cosmos-1408 satellite (Russian anti-satellite test)	2021	~480 km	About 1,800 trackable debris, forcing the ISS crew to take shelter in their capsules
Explosion of the Long March 6A upper stage (Yunhai-3 mission)	2022	~830 km	About 793 catalogued fragments, one of the most significant events of the decade
Fragmentation of the Russian satellite Cosmos-2499	2023	~1,170 km	Second known fragmentation of this satellite, generating numerous debris in low orbit
Fragmentation of the Resurs-P1 satellite (Russia)	2024	~355 km	More than 100 debris generated, forcing the ISS crew to take shelter
Explosion of the Intelsat 33E satellite in geostationary orbit	2024	~35,786 km	Several hundred fragments detected, threatening satellites in geostationary orbit
Explosion of a second Long March 6A rocket stage	2024	~800 km	At least 700 new debris, most of which will remain in orbit for decades
Starlink satellite anomaly (probable explosion)	2025	~418 km	Loss of 4,000 m altitude and generation of dozens of fragments; satellite out of control

Kessler syndrome: Alarming projections of risks

A catastrophic scenario imagined in 1978

The Kessler syndrome is a catastrophic scenario proposed in 1978 by the American astrophysicist Donald J. Kessler (1940-). It describes a domino effect in space where the density of space debris in Earth orbit becomes so high that collisions between objects generate even more fragments, creating an uncontrollable chain reaction. In the long term, some orbits could become unusable for decades, threatening GPS navigation, telecommunications and Earth observation.

Main consequences of space debris

Multiple impacts on space activities

Collisions with operational satellites and the saturation of low orbit constitute the two most immediate threats.

Saturation of low Earth orbit (LEO) by thousands of hyper-velocity fragments.
Increased risk of collisions with operational satellites, threatening telecommunications, navigation (GPS) and Earth observation.
Blocking access to space for decades, rendering certain orbits unusable.

Table of consequences of space debris

The table below summarizes the main consequences of space debris on space and terrestrial activities.

Consequences of space debris
Consequence	Affected domain	Concrete example	Potential impact
Risk of collision with active satellites	Telecommunications and navigation	Starlink performed more than 300,000 avoidance maneuvers in 2025; a collision could occur every 2.8 days if operators lose control	Loss of GPS, Internet and telephone services; saturation of low orbit
Increase in space mission costs	Space industry	The debris tracking and removal market reached 1.1 to 1.2 billion dollars in 2025; a removal mission costs about 90 million dollars per object	Higher launch, insurance and satellite operation costs
Risk to astronaut safety	Human spaceflight	The return of the Chinese Shenzhou-20 mission was delayed in November 2025 after a probable micro-debris impact on the spacecraft	Immediate life-threatening danger in low Earth orbit (LEO) for crews
Blocking of certain orbits	Earth observation	The Kessler syndrome, now documented by ESA, could render low orbit unusable; the space environment health index has deteriorated by an order of magnitude in one year	Loss of access to strategic orbits for decades
Pollution of the space environment	Sustainability of space	68,450 objects larger than 10 cm are tracked in 2025, to which are added 1.5 million fragments between 1 and 10 cm and 230 million millimeter-sized fragments	Threat to the future of space activities and exploration
Threat to future generations of satellites	Constellations being deployed	Starlink has more than 9,400 satellites in orbit and OneWeb about 654; these constellations must plan regular maneuvers (41 per year per satellite for Starlink)	Increasing complexity of space traffic management and cascading risks
Risk of uncontrolled fall to Earth	Ground safety	At least one space object falls back to Earth every day; in 2025, a Chinese rocket debris was found near a mine in Australia, and a 500 kg metal ring fell in Kenya	Material damage or injuries, with increased risk as orbital traffic grows
Scientific disruption	Astronomy and sky observation	According to a study published in Nature in 2025, 96% of images from certain space observatories could be contaminated by satellite trails within ten years	Drastic decline in the quality of astronomical surveys and loss of scientific data
Geopolitical risk	International security	China accused Starlink satellites of dangerous approaches twice near its space station; mega-constellations are perceived as a threat to sovereignty and regional stability	Increased tensions between space powers and difficulties in international cooperation

Solutions considered to limit the problem

Two complementary axes: mitigation and remediation

To prevent near-Earth space from becoming a veritable dumping ground, space agencies and companies are working on various solutions. Two main axes stand out: avoid adding new debris and clean up those already there.

Main technical and political solutions

The solutions are divided between mitigation and remediation, complemented by international coordination measures.

Mitigation: to avoid creating more debris, when a satellite completes its mission, it should be removed from its orbit instead of being left abandoned. International rules recommend bringing it down into the atmosphere within 25 years, where it burns like a shooting star.
Remediation: to recover existing debris, projects are testing nets, harpoons or robotic arms capable of capturing a debris to make it fall toward Earth. In 2018, a European mission, RemoveDEBRIS, proved this was possible.
Use of ground-based lasers: the idea is to point a laser from the ground to give a small push to debris, enough to modify their orbit and make them fall back faster.
Electric propulsion and braking sails: some satellites could carry large sails that increase air resistance, helping them descend faster at end of life.
International coordination: no nation can manage this problem alone. That is why the UN and several international organizations are trying to impose common rules to make all space actors accountable.

Scenarios for the evolution of space pollution

Three possible trajectories

The future of the orbital environment depends directly on the choices made today regarding debris management. Three main scenarios are envisaged by experts:

Optimistic scenario: strict application of international rules (deorbiting after 25 years, passivation of stages, better launch coordination). In this case, debris density could stabilize at a manageable level, allowing sustainable use of circumterrestrial space.
Trend scenario: continuation of the current rate of launches and debris production, with only partial mitigation efforts. We would see a slow but continuous increase in fragments, making certain orbits increasingly risky and costly to exploit.
Pessimistic scenario: multiplication of accidental or deliberate events (collisions, anti-satellite tests), triggering a Kessler syndrome. Chain collisions could render low Earth orbit (LEO) largely unusable for decades, with a major impact on telecommunications, navigation and scientific research.

Inaction, a risk of runaway

These scenarios show that inaction greatly increases the risk of uncontrollable runaway. Conversely, rapid and ambitious international cooperation can maintain space as a common good accessible to future generations.

References

FAQ: Everything you need to know about space debris

What is space debris?

Space debris is an artificial object in orbit around Earth that no longer serves any useful function. It can be a decommissioned satellite, an abandoned rocket stage, a fragment from a collision or explosion, or a piece lost during a space mission. A distinction is made between catalogued debris, whose size generally exceeds 10 cm, and micro-debris, too small to be tracked individually but capable of causing significant damage.

How many space debris are currently in orbit?

Surveillance networks identify more than 36,000 objects larger than 10 cm in Earth orbit. To this are added about one million objects between 1 and 10 cm and several hundred million fragments smaller than one centimeter, estimated by statistical modeling. The vast majority is concentrated in low Earth orbit (LEO), between 600 and 1,000 km altitude, where most observation satellites and telecommunications constellations circulate.

What is the Kessler syndrome?

Proposed in 1978 by astrophysicist Donald J. Kessler, this scenario describes a runaway of collisions in orbit. When debris density becomes too high, each collision generates new fragments, which in turn produce others. This chain process could render certain orbits unusable for decades, threatening telecommunications, satellite navigation and Earth observation.

Can space debris fall back to Earth?

Yes, but most disintegrate in the atmosphere. In low orbit, debris undergoes slight atmospheric drag that gradually brings it down. Small fragments burn up entirely during re-entry. More massive objects, such as rocket stages or certain satellites, can reach the ground. These falls remain statistically very rare, but recent cases, such as the fall of Long March rocket debris in 2020 and 2022, have revived concerns.

Are there solutions to clean up orbit?

Several approaches are being studied. Mitigation consists of not creating new debris, by deorbiting satellites at end of life and passivating rocket stages. Remediation aims instead to remove existing debris, using nets, harpoons, robotic arms or ground-based lasers. The European RemoveDEBRIS mission demonstrated in 2018 the feasibility of some of these techniques. No solution is yet deployed on a large scale.

Why is international cooperation essential?

Circumterrestrial space is a common good that knows no borders. Debris created by one country can threaten the satellites of all others. No nation can therefore manage the problem alone. The recommendations of the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), as well as the guidelines of the Inter-Agency Space Debris Coordination Committee (IADC), aim to harmonize practices. Their effective implementation remains a major political challenge.