Most space debris is not the result of slow wear and tear. A surprising amount of it was created in a few seconds, by a handful of events that each turned a single satellite into thousands of fragments. Understanding these events is the best way to understand why debris has become one of the biggest problems in spaceflight — and why Kessler syndrome is taken seriously.
These are also the clouds you can isolate on SatFleet Live: each one has its own filter in Space debris mode, so you can see exactly where its fragments are right now.
Fengyun-1C: The Worst Debris Event Ever
Fengyun 1CFengyun-1C was an old Chinese weather satellite in a polar orbit. In January 2007, China destroyed it with a ground-launched missile in a test of its anti-satellite (ASAT) capability. The impact turned a single spacecraft into the largest debris cloud ever catalogued.
The altitude made it far worse. At around 865 km, the upper atmosphere is so thin that fragments lose speed extremely slowly, and the orbit sits in one of the busiest bands used by Earth-observation and weather satellites. Nearly two decades later, a large share of the cloud is still being tracked, and it has spread from a tight cluster into a full shell surrounding the planet.
Iridium 33 vs. Cosmos 2251: The First Satellite Collision
Iridium 33 Cosmos 2251This one was not a test. Over northern Siberia, Iridium 33, an active American communications satellite, collided with Cosmos 2251, a Russian military satellite that had been dead and uncontrolled for years. They met at nearly 12 km/s, and both were destroyed instantly.
It was the first accidental collision between two intact satellites, and it proved that the scenario Donald Kessler had warned about in 1978 was not theoretical. Its two debris clouds are still in orbit today, which is why SatFleet Live gives each of them its own filter: you can compare how the fragments of each satellite have spread differently.
Close approaches between satellites happen constantly. At the time, predictions of a near miss between these two were not flagged as high-risk, and Cosmos 2251 had no way to manoeuvre. The collision is one of the main reasons operators now receive far more systematic conjunction warnings.
Cosmos 1408: The Test That Threatened the ISS
Cosmos 1408In November 2021, Russia destroyed its defunct Cosmos 1408 satellite with a missile. The fragments spread across orbits that crossed the path of the International Space Station, and its crew was ordered to shelter inside their docked spacecraft, ready to leave if the station was hit.
Because the test happened much lower, at around 480 km, the atmosphere worked faster. Most of the trackable fragments have already re-entered, and the cloud is now a fraction of its original size. It is the clearest illustration of how much altitude decides the damage: a similar test at Fengyun-1C's height would still be a problem in the next century.
Rocket Bodies: The Slow-Motion Problem
Rocket bodiesNot every debris source is a single dramatic moment. Since the first launches, upper stages of rockets have been left in orbit after delivering their satellites. They are the largest and heaviest objects in the debris catalog, and some have exploded years later because of leftover propellant or pressurised tanks, creating clouds of their own.
Experts often single them out as the most dangerous objects in orbit, because a collision involving a multi-tonne stage would produce far more debris than any test so far. We cover them in detail in Rocket Bodies in Orbit.
Other Breakups and Anti-Satellite Tests
Several other events have added to the problem, and their fragments appear on the map under Other debris:
The United States shot down a failing satellite at very low altitude. Its debris re-entered within months.
India destroyed one of its own satellites at around 300 km. Most fragments fell back quickly, though some were thrown into higher orbits.
A Chinese rocket stage broke apart in low orbit shortly after launch, creating hundreds of trackable fragments in a band already crowded with satellites.
A communications satellite broke up in geostationary orbit, about 36,000 km up, where there is no atmosphere at all to clear the fragments.
What These Events Teach Us
Altitude is everything. The same type of event can be a temporary nuisance at 300 km or a problem for a century at 850 km. See How Satellite Orbits Work for why.
One event can outweigh decades of routine operations. A single missile test created more trackable debris than years of normal launches.
Debris spreads. Every cloud starts as a tight cluster and slowly smears into a shell around the whole planet, crossing the paths of satellites at every orbital angle. That is the mechanism behind Kessler syndrome.
And for anyone on the ground wondering about falling pieces: most fragments from these events are small and burn up completely when they re-enter. The real odds are covered in Can Space Debris Hit You?
See Each Debris Cloud Live
Open the SatFleet Live map and switch to Space debris mode. The origin filters let you turn each cloud on or off — Fengyun 1C, Cosmos 2251, Iridium 33, Cosmos 1408, Rocket bodies and Other debris — and the size filter splits them by radar cross-section into large, medium and small. Show only one cloud at a time and rotate the globe in 3D to see how far it has spread. The data comes from Space-Track.org and refreshes twice a day.
Frequently Asked Questions
What was the worst space debris event in history?
The Chinese anti-satellite test that destroyed the Fengyun-1C weather satellite in January 2007. It created more than 3,000 trackable fragments at around 865 km of altitude, the largest debris cloud ever recorded, and much of it is expected to stay in orbit for decades.
Have two satellites ever collided in space?
Yes. On 10 February 2009, the active communications satellite Iridium 33 and the defunct Russian military satellite Cosmos 2251 collided at about 790 km over Siberia. It was the first accidental collision between two intact satellites and produced more than 2,000 trackable fragments.
What was the Cosmos 1408 anti-satellite test?
In November 2021, Russia destroyed its defunct Cosmos 1408 satellite with a ground-launched missile at around 480 km. The test produced more than 1,500 trackable fragments and forced the crew of the International Space Station to shelter in their spacecraft. Because of its lower altitude, most of that debris has since re-entered.
Is debris from Fengyun-1C still in orbit?
Yes. At around 865 km the atmosphere is too thin to remove fragments quickly, so a large share of the Fengyun-1C debris is still being tracked today and much of it will remain for decades. You can see it live on SatFleet Live in Space debris mode.
Why are anti-satellite tests so damaging?
A missile strike shatters a satellite into thousands of pieces that spread into new orbits, crossing the paths of other satellites at speeds of around 10 km/s. The higher the test, the longer that debris lasts, and each fragment raises the risk of further collisions.
How can I see these debris clouds?
Open SatFleet Live's live map and switch to Space debris mode. Filters let you show or hide the Fengyun 1C, Cosmos 2251, Iridium 33 and Cosmos 1408 clouds, rocket bodies and other debris, and filter by radar size. The data comes from Space-Track.org and refreshes twice a day.
Isolate Any Debris Cloud in 3D
Fengyun-1C, Iridium 33, Cosmos 2251, Cosmos 1408 and every rocket body — free, live, no account required.
Open Space Debris Mode