Space Debris: The Growing Problem of Orbital Junk

Space debris, also called space junk or orbital debris, refers to defunct satellites, spent rocket stages, fragments from collisions, and other human-made objects orbiting Earth with no useful purpose. Since the dawn of the space age in 1957, decades of launches have left a growing cloud of debris that poses a real threat to active spacecraft, astronauts, and the long-term sustainability of Earth orbit.

How Much Debris Is Up There?

The U.S. Space Surveillance Network tracks more than 30,000 objects larger than 10 centimeters in low Earth orbit. Statistical models estimate an additional 500,000 pieces between 1 and 10 centimeters, and over 100 million particles smaller than 1 centimeter. Even a centimeter-sized fragment carries enough kinetic energy at orbital speeds (roughly 28,000 km/h in LEO) to seriously damage or destroy a satellite.

Where Does Debris Come From?

• Spent rocket stages: Upper stages left in orbit after deploying their payloads are one of the largest classes of debris.
• Defunct satellites: Satellites that have exhausted their fuel or suffered system failures remain in orbit for years or decades.
• Collisions: The 2009 collision between Cosmos 2251 and Iridium 33 created over 2,000 tracked fragments.
• Anti-satellite tests: Deliberate destruction of satellites, such as the 2021 Russian ASAT test on Cosmos 1408, generates hundreds of new tracked debris objects in a single event.
• Paint flakes and microparticles: Thermal cycling and micrometeorite impacts erode spacecraft surfaces, shedding tiny but damaging particles.

The Kessler Syndrome

In 1978, NASA scientist Donald Kessler proposed a scenario in which the density of objects in orbit reaches a tipping point: collisions produce more fragments, which cause more collisions, creating a runaway cascade. If the Kessler syndrome were to occur, entire orbital bands could become unusable for generations. While we have not reached that threshold, the growing number of objects in LEO makes debris mitigation increasingly urgent.

Tracking Debris on Track The Sky

Track The Sky includes a space debris and fragmentation event tracker that visualizes known debris objects on the 3D globe alongside a timeline of historic collision and ASAT test events. The conjunction alert system monitors close approaches between any two tracked objects, showing how close passes happen regularly in crowded orbital regions. You can also use the reentry tracker to monitor objects losing altitude due to atmospheric drag, watching them spiral down toward atmospheric reentry.

What Is Being Done?

International guidelines now encourage operators to deorbit satellites within 25 years of mission completion. Agencies like ESA are developing active debris removal missions, and companies are testing technologies like nets, harpoons, and robotic arms to capture and deorbit large debris. SpaceX's Starlink satellites are designed to deorbit autonomously within five years if they fail, using atmospheric drag at their low operational altitude.

The debris problem is solvable, but it requires international cooperation and responsible practices from every spacefaring nation and commercial operator. By making debris data accessible and visual, tools like Track The Sky help raise awareness of this critical challenge facing the space environment.