Space junk is a collection of objects orbiting the Earth that were sent into space by humanity but no longer serve a functional purpose. These objects emerged as a by-product of space exploration and have become a serious threat over time. The first example of space junk was Sputnik I, orbited on October 4, 1957. After orbiting for three months, the satellite was operational for only three weeks and remained a dysfunctional piece of garbage the rest of the time. Today, space junk jeopardizes both active spacecraft and future space activities. This article examines the occurrence, sources, effects on spacecraft and monitoring challenges of space junk.
Formation and Sources of Space Debris
Space debris is created by two main mechanisms: orbital abandonment of spacecraft that have completed their missions and fragmentation as a result of collisions. Abandoned rocket stages, satellites and other objects collide with each other over time, breaking into smaller fragments. For example, on February 10, 2009, a defunct Russian satellite (Cosmos 2251) collided with an active US Iridium satellite, producing about 2,000 new pieces of debris. This event demonstrated the self-replication cycle of space junk. Other sources of debris include solid rocket engine dust, paint flakes, coolants leaking from the RORSAT nuclear satellites and Project West Ford clusters. The interaction of micrometeorites with spacecraft contributes to the formation of smaller debris particles. Low Earth Orbit (LEO), in particular, is one of the main concentrations of this debris.
The Dangers of Space Debris on Spacecraft
Space junk poses a significant risk to active spacecraft and satellites. Moving at high speed in orbit, these objects can cause serious damage in the event of a collision. An estimated tens of millions of small pieces of debris (such as paint flakes, rocket fuel residues) cause sandblasting-like surface abrasions. To mitigate these effects, thin layers of foil are added to spacecraft; the plasma from the collision vaporizes and protects the interior surfaces. However, sensitive components such as solar panels and optical devices lack this protection and are subject to constant abrasion. Larger pieces of debris can render spacecraft non-functional upon impact. For example, a 1 kg piece of debris can generate additional waste that creates new collision risks. Manned space missions are also affected by this hazard; while the International Space Station is protected from debris smaller than 1 cm, it may need to maneuver to avoid larger objects.
Space Debris Monitoring and Challenges
Monitoring space junk is a critical step to avoid collision risks. Systems powered by radars, telescopes and laser technologies determine the position and speed of orbiting objects. Structures such as the US Space Surveillance Network (SSN) generate warnings, anticipating potential collisions. However, current equipment cannot track objects smaller than 5 cm in Low Earth Orbit and 50 cm in Earth Stationary Orbit. Of the approximately 600,000 pieces of debris larger than 1 cm, only about 19,000 can be observed. These limitations create uncertainties in the estimation of debris trajectories. Measures such as maneuvering can only be implemented when the trajectory of the objects is known exactly, which necessitates the development of tracking systems.
