Space debris, also known as space junk, refers to defunct human-made objects in space—primarily in Earth's orbit—which no longer serve a useful function. These include spent rocket stages, old satellites, fragments from their disintegration, and other discarded equipment. As of now, there are about 128 million pieces of debris smaller than 1 cm, around 900,000 pieces between 1 cm and 10 cm, and approximately 34,000 pieces larger than 10 cm orbiting Earth. This accumulation poses a significant risk to active satellites, space missions, and the International Space Station due to the high velocities at which these objects travel, which can reach speeds of up to 28,000 kilometers per hour.
The issue of space debris started with the launch of the first satellite, Sputnik, in 1957, and has exponentially grown with the intensification of space activities. Notable events, such as China’s anti-satellite missile test in 2007 and the collision between Iridium 33 and Cosmos 2251 in 2009, have significantly increased the amount of debris. These events alone contributed thousands of pieces of debris to the near-Earth environment, highlighting the fragility and complexity of maintaining a clean orbital environment. Each fragment, regardless of size, has the potential to damage or destroy satellites and other spacecraft due to the kinetic energy involved in collisions.
Monitoring and managing space debris have become critical to the sustainability of future space operations. Organizations like the United States Space Surveillance Network and the European Space Agency's Space Debris Office track objects as small as 2 cm in low Earth orbit and 10 cm in geostationary orbit. There are various collision avoidance strategies, such as maneuvering satellites to avoid predicted collisions and designing new satellites to withstand impacts. Additionally, there are emerging technologies and ideas, including lasers to nudge debris off collision courses, nets, and harpoons to capture and remove debris, and even satellites designed specifically to rendezvous with and deorbit large pieces of junk.
Despite these efforts, the problem of space debris remains a significant challenge. With the increasing number of satellites being launched each year, especially from private companies like SpaceX, which plans to deploy thousands of satellites for its Starlink internet service, the density of objects in space will continue to grow. This increase underscores the urgent need for comprehensive space traffic management and more effective debris mitigation standards globally. The long-term goal is to achieve a sustainable environment around Earth, which will be critical for the safety and success of future explorations and satellite services. Ensuring the orbital environment is clean and safe not only protects current space assets but also secures the future of space exploration endeavors.