Space Debris Is Piling Up in Orbit and Could One Day Lock Us and Our Satellites on Earth

The oldest piece of tracked space junk still in orbit is Vanguard 1, an American satellite launched in 1958 that stopped transmitting in 1964. It has been circling Earth for over six decades, doing nothing except taking up space. Around it, according to NASA and the European Space Agency, are approximately 27,000 objects large enough to be tracked from the ground, defunct satellites, spent rocket stages, fragments from explosions and collisions. Below the tracking threshold sit an estimated one million pieces between one centimetre and ten centimetres across. Each one travels at speeds between 7 and 8 kilometres per second in low Earth orbit. At that velocity, a paint fleck the size of a fingernail carries the kinetic energy of a bowling ball thrown at highway speed.
The debris field is not evenly distributed. Low Earth orbit, the band between roughly 200 and 2,000 kilometres above the surface, is the most crowded, because it is where most satellites operate. The International Space Station circles at about 400 kilometres and has had to perform debris-avoidance manoeuvres dozens of times. In 2021 alone, the ISS crew was directed to shelter in the Soyuz capsule three times as a precaution. Geostationary orbit, at 35,786 kilometres, has its own graveyard ring where retired satellites are nudged when they run low on fuel, parked rather than removed.In 1978, NASA scientist Donald Kessler published a paper describing what happens if orbital debris reaches a critical density. One collision produces fragments. Those fragments collide with other objects, producing more fragments. The cascade accelerates until the debris density makes certain orbital altitudes effectively impassable, not for years, but for centuries, because there is no atmosphere at those heights to drag fragments down. This is the Kessler syndrome, and it is no longer purely theoretical.
The first major collision it predicted happened in 2009, when an active American Iridium communications satellite struck a defunct Russian Cosmos satellite over Siberia. The impact generated over 2,000 trackable fragments. In 2007, China tested an anti-satellite weapon by destroying its own Fengyun-1C weather satellite, creating the single largest debris cloud in history, more than 3,000 trackable pieces, many of which will remain in orbit for decades. These two events alone added roughly 5,000 new tracked objects to the catalogue. The Kessler cascade does not require a dramatic trigger. Enough slow accumulation, and the chain reaction becomes self-sustaining without any single catastrophic event to start it.GPS navigation, weather forecasting, internet connectivity in remote areas, disaster early-warning systems, agricultural satellite data, all of it depends on satellites in the orbits most threatened by debris accumulation. For India, the consequences are direct. ISRO operates a constellation of Earth observation satellites, communication satellites, and navigation satellites under the NavIC system. The Chandrayaan and Mangalyaan missions launched from Sriharikota depend on the same orbital corridors that debris is filling. The upcoming Gaganyaan crewed mission, India's first human spaceflight programme, will carry astronauts into low Earth orbit, the most debris-dense zone.
ISRO has its own Space Situational Awareness Control Centre, established to monitor and respond to conjunction alerts, warnings that two objects are predicted to pass dangerously close. The agency performed a collision-avoidance manoeuvre for Chandrayaan-2's orbiter in 2022. These manoeuvres consume fuel, and satellites carry a finite amount. Every evasive burn shortens the operational life of the spacecraft. The debris problem is already costing missions years of service life, not just theoretical future access.Several technologies are in development for active debris removal. The European Space Agency's ClearSpace-1 mission, planned for launch in the coming years, aims to capture a single piece of rocket hardware and drag it into the atmosphere for reentry and burnup. Japan's Astroscale has tested magnetic capture systems for defunct satellites. These are proofs of concept, not solutions at scale, removing one object at a time from a field of millions.

The more immediate lever is preventing new debris. The Inter-Agency Space Debris Coordination Committee, which includes ISRO, NASA, ESA, and the space agencies of Russia, China, Japan, and others, has established guidelines recommending that satellites in low Earth orbit deorbit within 25 years of end-of-mission. Compliance is voluntary and inconsistent. SpaceX's Starlink constellation, which aims to put tens of thousands of satellites in low Earth orbit, has committed to autonomous deorbit capability and has demonstrated reentry of defunct units. Critics point out that the sheer number of Starlink satellites, over 6,000 already launched, changes the collision probability calculations regardless of deorbit plans.
Tracking is the other frontier. Ground-based radar and optical systems can reliably track objects above about ten centimetres. The gap below that threshold is where the real risk lives. A one-centimetre aluminium sphere at orbital velocity will punch through a spacecraft wall. No current system tracks objects that small at scale.The Kessler threshold is not a cliff with a precise edge. Modelling by NASA's Orbital Debris Program Office suggests that even if all launches stopped today, the existing debris population in certain altitude bands would still grow through collisions among objects already up there. The window for meaningful intervention is open, but the models indicate it narrows with each passing year of unmanaged launches and unremoved hardware.

India has a specific stake in this beyond the operational. ISRO's ambitions, Gaganyaan, the Chandrayaan-4 sample return mission, future lunar and deep-space programmes, require reliable, affordable access to low and medium Earth orbit. A degraded orbital environment does not affect all nations equally. Countries with the budget to track debris, manoeuvre satellites, and build redundancy into their constellations absorb the cost more easily. Agencies operating on tighter margins, as ISRO famously does, carry the risk more sharply.
The arithmetic of the debris problem is uncomfortable: the objects already in orbit outnumber the capacity to remove them by orders of magnitude, the technology to close that gap does not yet exist at scale, and the incentive structure of commercial spaceflight keeps adding to the total. What the Kessler syndrome actually threatens is not dramatic, no Hollywood fireball, no single catastrophic day. The more plausible outcome is a slow narrowing of what is accessible, altitude band by altitude band, until the cost of operating in orbit becomes prohibitive for everyone except the largest programmes. By then, the junk will have been circling long enough that no one alive remembers when the sky was clean.