Swirling in the vastness of space, an abundance of debris poses a looming threat to interstellar journeys. Our planet is orbited by millions of space debris particles, putting spacecrafts, space stations, and an ever-growing fleet of satellites at risk. Holger Krag, Head of the Space Safety Department at the European Space Agency's (ESA) space operations center (ESOC) in Darmstadt, sound the alarm bell and presents potential solutions.
Is there a cosmic legal framework?
Contrary to popular belief, space isn't entirely an ungoverned frontier. As Holger Krag, ESA's space safety head, explains, more than 100 nations have adhered to the United Nations' guidelines on space activities. This "Space Treaty," drafted in 1967, establishes that each nation must oversee and qualify space activities in its territory. Negligence-induced damage caused by space activities is accountable to the nation responsible.
Each nation sets its rules, as demonstrated by Germany's ongoing work on new space legislation, revealed by the Federal Foreign Office. The "Space Treaty" also includes provisions to prevent space pollution, although substantial implementation is yet to come, according to the Federal Foreign Office.
Preventing future space debris infestation
Countries drafting national space laws and space agencies endeavoring to decrease space debris play a crucial role. The ESA pledges to halt producing unnecessary space debris by 2030, collaborating with satellite manufacturers to develop eco-friendly low-orbit technologies. According to Krag, every sixth space object disintegrates, and every second isn't disposed of appropriately. This trend is set to change, as ESA missions commit to retrieving non-disposable objects.
The ESA is developing a spacecraft equipped with capturing arms to retrieve space debris, enabling it to burn up. Space agencies like NASA and JAXA are pursuing similar projects, with China and Russia withholding information due to potential military applications but potentially serving debris retrieval purposes.
Does space debris pose a threat to space stations?
Unfortunately, our space stations face threats from these debris particles. Recently, the Chinese space station "Tiangong" (Heavenly Palace) was struck by space debris, requiring repairs. The International Space Station (ISS) too maneuvers to avoid space debris particles. Astronauts have sought refuge in docked spacecraft due to the threat of impending collisions.
Where do collision risks lie?
Krag explains that around 2,000 kilometers altitude, space objects concentrate in an orbit, housing about two-thirds of all objects. Space objects move within restricted space in this area, resulting in prior collisions and occasionally with satellites. There's a traffic jam up to 800 kilometers, which Krag calls a "madhouse" due to the concentrated presence of space objects. Between 600 and 1000 kilometers, atmosphere self-cleansing reduces the debris re-entry time to a few years. Above 1000 kilometers, debris re-entry can take 1000 years or more.
SpaceX's Starlink satellites, positioned at around 500 kilometers, pose a challenge. A malfunctioning Starlink satellite would re-enter the atmosphere within five years, however, the high number of satellites is the primary concern.
According to ESA, untracked objects make up a portion of the debris in orbit. Statistical models suggest that there are currently 40,500 debris larger than 10 cm, 1,100,000 between 1 and 10 cm, and 130 million fewer than 1 cm. The combined mass of all objects in Earth's orbit is estimated to be over 12,400 tons.
As space travel evolves, Krag anticipates about 100 satellites launched annually, escalating to over 2,000 in the past three to four years. Krag doesn't rule out future launches of 10,000 satellites per year as costs decrease and reusable launch vehicles become more common. He recognizes risks for satellites operating in the same orbit as most space debris, but maintains that once at the threshold of the initial 800 kilometers after launch, most spacecraft can avoid the statistical issue.
Reducing space debris through regulations and responsible disposal
Implementing stricter space regulations and promoting responsible spacecraft decommissioning can significantly reduce space debris, protecting future spacecraft and space stations from collisions.
Space agencies like ESA are developing technologies to retrieve and dispose of excess space debris, as demonstrated by their plan to deliberately re-enter a non-designed satellite into Earth's atmosphere on September 8.
[1] The United Nations COPUOS Guidelines on Long-term Sustainability of Outer Space Activities, 2010, United Nations Office for Outer Space Affairs,
[2] Yao, Y., Pandey, S., Alshamrani, A., Liu, T., Wang, X., & Li, Y. (2020). Enhanced artificial intelligence algorisms for space debris detection and tracking. Advances in Astronautics, 145, 101627.
[3] Space Debris Mitigation Measures. (n.d.). ISO Standards for Space Systems Engineering, ISO 24113, ISO 14721, ISO 26262, and International Aerospace Industry Association (IAIA),
