Space debris is growing from being a nuisance to becoming a threat. In the past, states launched objects into outer space without consideration for environmental effects or collision risks. Today, there is more awareness that outer space must be kept safe and clean for future use, and technical and legal rules for debris mitigation and remediation are needed.

Satellites usually operate for 10-15 years and are then left in space. Currently, some 20,000 objects larger than 5 cm in diameter are being tracked. Eventually they will re-enter the earth’s atmosphere, but depending on the size of the object and the height of the orbit, this can take a very long time.

Spent satellites can cause damage on earth, as the Cosmos 954 crash in Canada in 1978 demonstrated. Article II of the 1972 Liability Convention provides that in such a case the liability of the launching state is absolute.

Non-manoeuvrable debris can also collide with active satellites while in space, as seen during a head-on collision in 2009. The ISS had to carry out several manoeuvres to avoid debris. Another (partial) collision took place on 23 May 2013 and incapacitated Ecuador’s first satellite. Article III of the Liability Convention provides for fault liability in such cases. This can be a challenge hundreds of kilometers up in space, which perhaps explains why there is no case law. Damage has to be caused by a space object (does that include an inactive satellite or a lost screw driver?) to a space object, persons or property of another state. Environmental damage to space does not seem to be covered, but Article IX of the 1967 Outer Space Treaty does require states to enter into consultations when harmful contamination may occur.

The UN and debris mitigation

In 2007 the UN adopted the Space Debris Mitigation Guidelines. These non-binding guidelines can become binding through incorporation into national law, and could become customary law with sufficient state practice and opinio iuris. Although ‘hard law’ protagonists will argue that a new treaty is needed, the prospects are not so good. The last UN space treaty dates back to 1979 and has only 15 state parties. Admittedly, that treaty addresses the controversial issue of commercial exploitation of space resources, and consensus on a space debris mitigation treaty might be easier. Of course a treaty would be the ideal solution in the long run. The term ‘space object’ must be clarified to include inactive satellites, which remain the responsibility of the state and may give rise to liability for damage, even if they cannot be controlled. Binding rules may provide an incentive for states to boost their satellites to higher (unused) orbits or to de-orbit them so they burn up.

Next step: debris remediation

Calculations indicate that if 5 large objects are removed each year, the cascading effect predicted by Kessler could be halted. To reverse the trend, 10 large objects need to be removed each year. Hence, ‘active debris removal’ (ADR) is the next step, and several technical solutions are on the drawing board of public and private entities. They include nets, harpoons, tethers and more (see this movie about a Swiss solution). Commercial, legal and policy issues are manifold. Students of Leiden University’s LLM programme in Air and Space Law recently visited Dutch Space, an EADS Astrium company, which is also active in this field. Technical and legal challenges of active debris removal were addressed. Legal issues include questions of ownership, prior permission, liability, payment, security, insurance and the like. An analogy with marine law, especially the salvage and wreck removal conventions of the International Maritime Organisation, as well as with international environmental law are of interest in this context. This confirms once more that space law is not an isolated field but must be seen in the broader context of many other legal disciplines.