Middle Temple Young Barristers' Association


Edmond Boulle



In the 2013 Hollywood blockbuster ‘Gravity’ two astronauts played by Sandra Bullock and George Clooney are the sole survivors of a disaster that leaves the rest of the crew dead and their spaceship, the Shuttle Explorer, catastrophically damaged. The disaster is brought on when fragments from a defunct Russian satellite, exploded by the Russians in an anti-satellite weapons test, collide with the American spaceship. 

The film’s writer and director, Alfonso Cuarón, was no doubt inspired, at least in part, by real life events. In January 2007 the People’s Republic of China destroyed a non-operational Chinese weather satellite, FY-1C, using an anti-satellite missile launched to an altitude of 865km. The following year, in February 2008, the US government used a ballistic missile to intercept a defunct reconnaissance satellite at an altitude of 240km prior to its re-entry into Earth’s atmosphere. On each occasion the kinetic force of the impact created a cloud of fragments of varying sizes and trajectory travelling through space at tremendous velocity. 

‘Gravity’ succeeded in bringing to the public’s attention the phenomenon often referred to as ‘space debris’ or ‘orbital debris’. In fact, Cuarón’s work displayed almost prophetic vision. On 16th July 2015, life came worryingly close to imitating art, when the crew of the International Space Station (ISS) were forced to enter the Soyuz escape module as an emergency precaution in response to passing fragments from a non-operational Russian weather satellite. It is in fact the fourth time that an ISS evacuation has been imminent as a result of space debris. Moreover, since launching in 1998, the Station has had to manoeuver to avoid approaching space debris no fewer than 22 times. 

In the typical style of a Hollywood movie, the focus of ‘Gravity’ is on the potential human cost of space debris. In reality, space debris poses a far more significant threat to the numerous civil and military satellites orbiting the Earth in ‘congested’ orbits. Some facts and figures may help to elucidate this point: 

In almost six decades of spaceflight since Sputnik 1 was launched, nearly 7,000 satellites have been put into orbit of which around 3,600 are still in space. Approximately 1,000 of these are no longer operational. However, the concept of space debris is not restricted to decommissioned or failed satellites. The Inter-Agency Space Debris Committee has defined space debris as all non-functional, man-made objects, including fragments and elements thereof, in Earth orbit or re-entering the Earth’s atmosphere. The sources of space debris also include in-orbit explosions from unstable fuel sources, intentional release of objects during a space mission, spacecraft surface erosion, particles ejected from solid fuel rocket engines during in-orbit manoeuvres and anti-satellite weapons testing. Another significant source of space debris comes from in-orbit collisions. On 10 February 2009 a non-operational Russian satellite, Kosmos-2251, collided with an operational American satellite, Iridium-33, at 776km above the Earth’s surface. The total impact speed was estimated to be 42,120km/h. The collision produced over 2,000 pieces of debris with a length of 10cm or greater, each capable of total destruction of a satellite or spacecraft, as well as many thousands of smaller pieces of debris of less than 10cm capable of inflicting serious damage. 

Various space agencies cooperate to catalogue and monitor space debris in order to provide an early-warning mechanism to satellite operators (known as ‘space situational awareness’). The European Space Agency continually tracks about 23,000 pieces of space debris greater than or equal to 10cm in length. Beyond that, estimates for the total amount of debris vary considerably (400,000 – 750,000 pieces of debris between 1cm and 10cm; and 35,000,000 – 100,000,000 pieces of debris of less than 1cm). In the vastness of space even 100,000,000 pieces of debris may at first appear insignificant. However, the threat is particularly acute because the great majority of operating satellites (and hence most orbital debris) are located within relatively narrow orbital bands according to their function. To generalise somewhat, earth observation satellites tend to be placed in a Low Earth Orbit (LEO) at an altitude of 160 - 2,000km, close enough to accurately use their remote sensing instruments, while communications and meteorological satellites are typically placed in Geosynchronous Orbits (GSO) around 35,000 – 36,000 km from Earth so that they remain in the same position relative to a point on the Earth’s surface. 

Narrowing our view of space to these functional orbital bands, the threat posed by space debris is suddenly much more stark. The problem is further compounded by a phenomenon referred to as ‘collisional cascading’ or the Kessler syndrome: A self-sustaining process whereby debris generated in a collision subsequently collides with other debris or space objects, leading to an ever increasing fragmentation of the debris population. Put simply, the amount of space debris is increasing while the natural decay of orbits (causing objects to burn up in the Earth’s atmosphere) is not enough to compensate. Consequently, space debris poses a serious hazard to governments, international organisations and private commercial and non-commercial entities wishing to carry out space activities. 

Moreover the situation is made more critical by the entrance into the market of an increasing number of non-governmental entities including universities, research organisations, SMEs and large multi-national corporations, enticed by the fast-growing global market for satellite data and derived applications and the plummeting cost of access to space and space technologies. Most recently Space X and OneWeb have announced their intentions to launch LEO constellations of 4,000 and 650 microsatellites respectively in a race to provide broadband internet access to remote parts of the world. OneWeb raised $500m of funding from backers including Virgin Galactic and Airbus Defence and Space for a project estimated to cost between $1.5bn and $2bn. Satellites have become commodities capable of sustaining billion-dollar businesses through lucrative contracts, negotiated by satellite operators, to access and use the data they send back to Earth. Meanwhile, certain categories of off-the-shelf satellites, such as CubeSats or NanoSats, have made space accessible to SMEs, universities and research organisations. Against this backdrop the issue of liability for damage caused by space debris to satellites in orbit have assumed a great deal of significance.


The following two sections of this article shall consider some of the issues a private entity, such as a commercial satellite operator, might encounter if it were to seek to recover damages for loss of a satellite as a result of a collision with orbital debris. 

Identifying the source of the debris 

The commercial satellite operator would first have to ascertain the source of the debris to identify the potential defendant. In practice, this factual enquiry would sometimes present an insurmountable obstacle. As mentioned above, certain space agencies track some (but by no means all) debris as part of space situational awareness programmes. As well as location data, the monitoring programme may include data on the origin of a piece of debris where this has been notified by a State participating in the programme or where it is self-evident from the circumstances in which it was created (e.g. following a fuel explosion on board a satellite whose location is known). In many cases the source of smaller fragments of debris would remain a mystery or would not be capable of proof, effectively preventing any claim from being brought. 

However, let us assume that the origin of the offending piece of debris is ascertainable and that the space agency holding that information is willing to share it with the stricken party. The commercial satellite operator (the ‘claimant’) would be faced with the difficult question of where to go to seek a remedy. There is unfortunately very little clarity, and no established practice or precedent, concerning the appropriate forum for pursing a claim for damage sustained in outer space. 

Recourse at national level 

If both parties to the dispute are private entities the claimant might try to bring a claim in national courts. However, there are a number of potential legal obstacles in doing so: 

- It is reliant on the national court to which the claim is submitted accepting jurisdiction. 

- It is uncertain how conflict of law rules would apply to determine the applicable national law when the damage occurred in outer space. 

As well as practical considerations: 

- The defendant may not be covered by third party liability (TPL) insurance at the time of the collision. Not all States require satellite operators to carry TPL insurance as part of national licensing requirements for space activities and those that do (such as the UK) typically mandate TPL insurance to cover the launch and first year of in-orbit operations only. 

- An uninsured defendant, especially an SME, university or research organisation may not have sufficient assets against which a judgment may be enforced. 

If the defendant is a public authority (e.g. a national space agency) then it will be protected via State immunity from being sued in a foreign court and may benefit from Sovereign immunity in national courts unless such immunity is waived.

The claimant must otherwise seek redress through the State. Here we enter the realm of public international law with its sub-division of legal instruments collectively referred to as ‘Space Law’. 

Liability in Space Law 

The basic or primary instrument of space law is the Outer Space Treaty 1967 (‘OST’). As of 2015, the OST has been ratified by 103 States (including all space-faring nations) and signed by a further 25 States. International treaties address States rather than their private entities. The drafters of the OST nonetheless recognised in 1967 that non-governmental (private) entities, as well as governmental entities, were involved in space activities. The OST (Article VI) therefore imposes the unusual burden on State Parties of general, international responsibility for all national activities in outer space, whether carried out by governmental agencies or private entities. 

Recognising the extremely hazardous nature of space activities (though not yet aware of the dangers posed by space debris), the State Parties also agreed the ‘liability principle’ (Article VII): State Parties are liable to other State Parties (or their natural or juridical persons) for any damage caused by a space objects or its component parts for which the State Party is the ‘launching State’. The term ‘launching State’ can describe four possible scenarios: 

(i) The State that launches an object 

(ii) The State that procures the launch of an object 

(iii) The State from whose territory and object is launched 

(iv) The State from whose facility an object is launched

It is therefore possible for more than one State to qualify as a launching State in respect of the same space object. 

In summary, the OST lays the foundations for a liability regime that makes launching States liable for damage done by governmental or non-governmental entities to other State Parties, their governmental or non-governmental entities. 

The Liability Convention 1972 

The OST’s liability principle has been significantly elaborated through a separate and subsequent international treaty known as the Liability Convention 1972. As of 2015, the Liability Convention has been ratified by 92 States (including all space-faring nations) and signed by a further 21 States. The Liability Convention establishes a victim-orientated lex specialis which goes beyond the provisions of the OST and public international law. Some of its key features are: 

- Joint and several liability of launching States (Article V) 

- Absolute liability for damage caused by a space object on the surface of the Earth or to aircraft in flight (Article II) 

- Fault based liability for damage caused by a space object in outer space (Article III) 

- Unlimited liability on the basis of restitutio in integrum (Article XII) 

- The possibility for claims to be presented by natural or juridical persons who suffer damage through their State of nationality or permanent residence (Article VIII) 

If, therefore, the claimant is a private legal entity of a State Party to the Liability Convention, that State will be entitled to bring a claim on behalf of the claimant against any or all States identified as launching States in respect of the space debris. The claimant State will not have the difficult burden of proving precisely which launching State caused the damage. Each launching State can be held independently liable for the full amount of compensation. 

The Liability Convention includes a mechanism for the settlement of disputes. Attempts should first be made to settle any claim through diplomatic channels. If settlement is not reached, a Claims Commission shall be established at the request of either party (Article XIV). A Claims Commission is an arbitral body with power to decide its own procedure and to make a final and binding award if the parties so agree (Articles XV-XX). 


The Liability Convention contains no specific reference to space debris. It contains only its general formulation of fault-based liability in respect of damage caused by a space object elsewhere than on the surface of the Earth. This section shall consider how that general formulation might apply to the specificities of damage caused by space debris. Two issues stand out for particular attention: First, is ‘space debris’ a ‘space object’ within the meaning of the treaty? Second, how is ‘fault’ to be assessed in such cases? 

Is debris a ‘space object’? 

The Liability Convention provides that a ‘space object’ includes component parts of a space object as well as its launch vehicle and parts thereof. However, the treaty offers no further definition of what constitutes a ‘space object’ or its ‘component parts’. It does not appear that whether an object is functional or not plays a part in its classification as a ‘space object’. A defunct or decommissioned satellite would remain a ‘space object’. More problematic is the definitional ambiguity surrounding what constitutes a ‘component part’. It is uncertain whether every fragment of debris is a ‘component part’ of a space object merely because it came from or was emitted by a satellite or other spacecraft. If ‘component part’ is a more restrictive concept, denoting something more than origin, then it will depend on the nature of the debris in each case. A fuel tank or protective fairing would be more likely to constitute a ‘component part’ of a space object than a small fragment of a solar panel broken off in a previous collision or a tool dropped by an astronaut during a space walk. 

Fault-based liability 

The Liability Convention provides that liability for damage caused in outer space should only arise where there is fault. Article III clarifies that the fault must be that of a launching State or of persons for whom it is responsible. The reference to fault is unusual in public international law. Liability in public international law normally attaches to the violation or breach of an international obligation. The reference to fault is puzzling because it presumes the existence of a recognised standard of care in international law against which actions may be judged. In fact, no such mandatory standard exists as a point of reference. Furthermore, the Liability Convention has never been invoked in any court, nor any Claims Commission set up, and hence no interpretation or clarification of fault has been offered (the Iridium-Kosmos collision described above was never formally settled). 

Even if claimant and defendant States to a particular dispute can agree on a standard of fault to be applied by a Claims Commission, a claimant is likely to face an uphill struggle to establish fault in any dispute involving space debris. Space debris is by its very nature beyond the immediate control or influence of any State or private entity; A launching State may well not have the resources or capability to continuously track the debris in order to provide an early-warning system to nearby third party satellites; The stricken satellite may in fact possess in-orbit propulsion but nonetheless fail to manoeuvre to avoid the oncoming debris (as was the case for Iridium-33). The situation becomes even more complex if the debris is itself the product of an earlier collision (Kessler syndrome). 

A claimant State might instead choose to argue that the space debris should not have been created or allowed to remain in orbit and thereby pose a threat to other operational spacecraft? There are unfortunately no binding international norms compelling States to ensure that space objects are safely disposed of at the end of their operational life. Instead, a considerable number of international instruments have developed that contain standards or guidelines on ‘space debris mitigation’1. 

1 Some prominent examples of space debris mitigation and standards include: the United Nations Space Debris Mitigation Guidelines 2007; the Inter-Agency Space Debris Coordination Committee Guidelines 2002; the European Code of Conduct for Space Debris Mitigation 2004; ISO standard 24113 ‘Space Systems – Space Debris Mitigation Requirements’. 

In essence ‘space debris mitigation’ deals with the management, design and operation of space missions to minimise new debris creation. It is a more developed and more technically feasible concept than ‘active debris removal’. Examples of space debris mitigation measures include: 

- Removing spacecraft from congested orbits by using residual fuel to send them into a safe ‘graveyard orbit’ where they will remain for millennia. 

- De-orbiting satellites in LEO to allow them to burn-up in the Earth’s atmosphere within 25 years after end-of-life. 

- Avoiding activities that create a risk of harm, including the intentional destruction of satellites. 

- Limiting the release of objects during a mission. 

- Passivation of fuel systems to avoid in-orbit explosions

None of these measures are legally binding under public international law (they are ‘soft law’). However, governments and space agencies are increasingly referring to them and make them applicable through national space legislation as part of governmental authorisation requirements to carry out space activities. 

There is scope for a claimant State to argue that a launching State was at fault by reference to these prevailing best practice standards or guidelines. Take, for example, the ‘Gravity’ scenario, in which a launching State intentionally destroys its satellite and thereby creates an increased risk of harm from debris. Similarly, an argument for fault could be made against a State that authorises a private entity to launch a space object whose design or operational parameters fall short of the recognised international standards. We might say that although a launching State is not bound by those standards it ignores them at its own risk2. 

2 Consistent with this analysis the UK regulator is currently considering waiving one of the prerequisites to obtaining a licence - TPL insurance up to €60m - for certain categories of satellite complying with debris mitigation guidelines: 

3 Though Space Law often draws its inspiration from the international law of the High Seas, there is no equivalent, for example, to the Nairobi International Convention on the Removal of Wrecks 2007 (in force 2015). 


Liability for damage caused by space debris in outer space occupies an increasingly important position in Space Law discourse. It is a matter that vexes satellite operators, insurers and national regulators and offers very few straightforward answers. 

Where legal or practical considerations prevent a claim from being pursued in national courts, a claim may yet lie at State level. Although there are no norms in public international law dealing specifically with liability for damage caused by space debris3, Space Law does possess a mechanism for compensating governmental and private entities who suffer loss as a result of third party space activities. However, it is untried and untested and appears to be an awkward fit for claims involving damage inflicted by space debris. 

At the time the Liability Convention was drafted space was largely the preserve of a handful of government space agencies. The dangers of space debris were not in contemplation, much less fully understood. The Liability Convention is therefore a blunt instrument, not particularly well-suited to claims involving space debris. In particular, it is uncertain whether the Convention’s notion of a ‘space object’ extends to fragments of space debris. Additionally, the Convention leaves open the question of what standard of fault ought to be applied. Consequently, a private entity wishing to recover compensation for a satellite destroyed or damaged by space debris will have to contend with a great deal of legal uncertainty. 

The author would like to thank the Middle Temple Young Barristers Association for its generous support towards his international internship at the European Space Agency (Legal Services Department) from 2013 – 2015. The author was the Executive Secretary to the European Centre for Space Law and is a member of the International Institute for Space Law. He currently works for the Satellite Applications Catapult in the UK. 

Background image by DAVID ILIFF. License: CC-BY-SA 3.0