International space law is a branch of public international law. Norms of treaty law and customary law provide a foundation for the behavior of the subjects of international law performing space activities. Five multilateral space treaties are in effect, which are complemented by important recommendations of international organizations such as United Nations (UN) General Assembly Resolutions and International Telecommunication Union (ITU) Regulations.
The Inter-Agency Space Debris Mitigation Coordination Committee (IADC), a non-governmental body composed of several space agencies (for instance, the European Space Agency, the United States National Aeronautics and Space Administration, the Japanese Aerospace Exploration Agency, the Russian Federal Space Agency), issued its Space Debris Mitigation Guidelines in 2002. The IADC defines “space debris” as “all man-made space objects including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional” (IADC, 2002, Revision 1, 2007, 3.1. Space Debris). Although the term “space debris” was not included in any space treaty, the drafters of the space treaties considered space objects as “hazardous” because “component parts of a space object as well as its launch vehicles and parts thereof” detach in course of normal launching operations, because space objects can fragment during an attempted launch, and because space objects that re-enter Earth’s atmosphere and survive friction have the potential to cause damage. In addition, radioactive and chemical substances on board space objects may represent a hazard to populations and the environment on the Earth.
Besides the threats to aircraft in flight and to persons and property on the surface of the Earth, space debris in orbit is increasing alarmingly and poses a threat to manned space missions and non-manned space objects. While the Convention on International Liability for Damages Caused by Space Objects (Liability Convention, 1972) considers the threats of space objects during launch, in outer space, and when entering the Earth’s atmosphere, there have been efforts to minimize the generation of space debris in orbit, outside the framework of the space treaties.
The IADC Space Debris Mitigation Guidelines are a comprehensive list of recommendations to launching states, owners, and operators of space objects. They are increasingly recognized by states through the creation of codes of conduct, national legislation, recommendations of international organizations, and state practice. Furthermore, non-governmental institutions, like the International Organization for Standardization, are providing more detailed technical instructions for the implementation of the Space Debris Mitigation Guidelines, which are a breakthrough for the application of the guidelines by states of different economic and technical standing.
Even though states are reluctant to accept new obligations through treaties, recommendations and state practice are becoming powerful instruments to avert the dangers of hazardous space debris that may create damage on the Earth or in orbit. Space debris also is becoming one of the drivers for the initiatives of the United Nations on the long-term sustainability of outer space activities to promote the existing mitigation guidelines and to formulate new guidelines for clearing outer space of debris.