On 15 October 2020, a non-operational Russian satellite and a discarded Chinese rocket stage segment came within 70 metres of colliding over Antarctica. With a combined mass of over 2,800 kilogrammes, a collision between these 2 pieces of space debris would have been destructive and may have produced a significant shower of debris fragments. Due to the objects' altitude, the resulting debris would have been likely to have remained in orbit for a significant period of time and increased the number and distribution of potentially dangerous space debris.
In the 60 odd years of space exploration following the Soviet Union's launch of its first satellite in 1957, space has become increasingly cluttered with derelict satellites, burnt-out rocket stages, discarded trash and other debris, prompting NASA to refer to the lower earth orbit (LEO) as an 'orbital space junk yard'. The European Space Agency recently estimated that there are 34,000 debris objects larger than 10 cm currently in orbit around Earth, along with 900,000 debris objects larger than 1cm.
The European Space Agency's Space Debris Office in its 2020 report on the current state of the debris environment provides that on average over the last 20 years, 12 non-deliberate fragmentation of space debris have occurred in space every year which have created new debris. These fragmentation events are caused by explosions in orbit (from fuel or batteries found in old spacecraft and discarded rocket sections), active space missions (which shed debris), and collisions between space debris and objects in space.
Orbital collisions are not the stuff of science fiction. In LEO, space objects including debris orbit at very high speeds; even a small piece of debris (e.g. a fleck of paint) may cause significant damage at such speeds. As collisions among objects can be highly destructive, there is a concern that without the effective remediation of orbital debris, the collisions will increase and increasingly threaten working satellites and space missions.
The commercial use of space is growing at an increasing rate. The launch of "mega-constellations" (some comprising thousands of satellites) will increase the problems associated with orbital debris. With the increased use of outer space and multiplication of space debris, the European Space Agency predicts that collisions between debris and working satellites will overtake explosions as the dominant source of debris. If LEO becomes too congested with space debris, the threat of collision raises critical questions of the viability of future space exploration prompting development of guidelines around debris remediation.
There is international recognition of the need to deal with orbital debris and to provide an adequate international framework to address the complex legal issues that it raises. Current space treaties do not provide an effective framework to regulate the issue of orbital debris and there is no effective international law regime regarding responsibility to mitigate debris creation, or the remediation of the orbital environment (and who bears the costs). Liability for damage caused by debris raises complex legal issues, with much interpretation left to individual entities (and their lawyers).
In order to fully appreciate the issues raised by the increased volume of space debris, it is important to understand the origins and management of space objects, as well as the factors contributing to the hazard of these objects colliding.
Space is vast. However, Earthling space activities are limited primarily to three orbital regions: LEO, Medium Earth Orbit (MEO) and Geostationary Orbit (GEO). An orbit is the curved path that an object in space takes around another object due to gravity. There are different factors which determine the decision as to the orbit in which a satellite is placed. Today, many communications, navigation, experimental and observation satellites are in LEO, including manned missions such as the International Space Station. The proximity of LEO satellites to Earth makes them achieve far lower latency than GEO satellites, making them ideal for high speed communications.
The US Strategic Command Space Surveillance Network (SSN) identifies, tracks and catalogues space objects larger than 10cm. Currently the SSN is tracking more than 16,000 man-made space objects. Fewer than 1,000 of these objects are operational. The remaining tens of thousands of objects are orbital debris comprising non-operational payloads, derelict rocket bodies, mission-related debris release and fragmentation debris from the disintegration of payloads or rocket bodies. The intentional destruction of satellites (such as the anti-satellite weapon test by China in 2007) may also significantly increase the debris population. More than half of catalogued space debris is fragmentation debris. As orbital debris smaller than 10 cm is not trackable with current radar technologies, the risk of collision risk may be underestimated.
Satellites are used for many different purposes, including meteorology, geology, climate research, telecommunications, navigation, remote sensing and human space exploration. Assisted by lower per-launch costs and cheaper satellite development, space opportunities for commercial companies beyond aerospace and defence are opening up. The expected commercialisation of space adds to the challenge of managing orbital debris. Various commercial companies such as SpaceX, OneWeb and Amazon have signalled their ambitions to deploy mega-constellations of thousands of small satellites in the lower earth orbit to provide affordable and reliable internet connectivity.
Space debris can remain in orbit for a very long time depending upon its size, nature and altitude. The higher the altitude, the longer the orbital debris will typically remain in the Earth's orbit. At typical collision speeds of 10km/s in orbit, subject to the size of the debris, a collision with space debris has the potential to damage critically or destroy operational satellites and manned spacecraft, including the International Space Station, threaten the safety of astronauts, deviate satellites from their orbits, threaten the functionality of operating satellites and accelerate the degradation of operational satellites. In 2020, the International Space Station (which resides in LEO) was forced to manoeuvre its path three times to avoid potential collisions with space debris. Not all orbital debris is trackable and therefore, it may not always be possible to manoeuvre from the path of the debris and avoid a collision. Whilst a significant amount of orbital debris is unlikely to survive the severe heating during re-entry to Earth, there is also a risk that large re-entering objects can cause potential safety and environmental threat to objects on Earth.
The significance of orbital space debris is more than an environmental issue. In 2020, the Organisation for Economic Co-operation and Development (OECD) published its first report on the economic cost of space debris. The OECD estimates that the economic expense of protecting missions from space debris amounts to an estimated 5 to 10% of the total mission costs for GEO satellites, which could be hundreds of millions of dollars. In LEO, the relative expense per mission could be even higher than 5 to 10%.
If LEO becomes too congested with space debris, the threat of impact raises critical questions of the viability of future space exploration. The OECD report critically states “the main risks and costs lie in the future, if the generation of debris spins out of control and renders certain orbits unusable for human activities.” The partial or complete loss of LEO may endanger launches to higher orbits, GEO and MEO, and eventually lead to the Kessler syndrome. The Kessler Syndrome posits that at a certain point, collisions between space debris could cause a cascading effect leading to exponential increase of space debris causing LEO to be unusable
Given the risks of not addressing orbital debris and the economic costs of space debris, international agencies, national authorities and private commercial enterprises have become increasingly involved in raising awareness and developing means to address the growth of space debris.
Debris mitigation requirements and practices that have been developed and adopted to guide launch and space object operators include limiting or minimising debris release for space systems through improved design. The measures also aim to focus on end-of-use satellite and rocket body disposal, and active detection of on-orbit collisions during mission planning (through the use of shielding to protect the spacecraft), as well as redirecting satellites post-mission towards re-entry to earth or moving satellites to graveyard orbits. Many States also require debris mitigation measures as part of the licensing process for space launchers and operators. In tandem with mitigation measures, active debris removal is necessary to reduce existing orbital debris. The European Space Agency has signed a contract with ClearSpace SA to remove orbital debris with the mission planned to remove its first debris by 2025.
However, it remains the case that as a matter of international law (i.e. as between States) there is no obligation to enforce debris mitigation or prevention measures; the mitigations adopted to date are voluntary on a State by State basis. Without an effective regime that provides necessary authority or power to force compliance, voluntary compliance with international guidelines to reduce space debris may be slow to encourage the necessary changes in the space industry and assist with minimising (or indeed clearing) orbital debris posing threats to the future of space activity.
Orbital debris is not addressed explicitly in current international law. As private commercial space activity increases, new risks and challenges arise in relation to space exploration.
Three treaties with potential relevance to orbital debris issues are the:
Three articles in the Outer Space Treaty contain language pertinent to orbital debris issues. Article VI requires that signatory nations to the Convention "bear international responsibility for national activities in outer space". Article VII makes signatory nations that launch or procures the launching of an object into outer space "internationally liable for damage caused by objects (and the component parts of those objects). Finally, Article IX requires signatory nations to "conduct all their activities in outer space … with due regard to the corresponding interests" of other signatory nations. Article IX also provides that studies by signatory nations (or their nationals) of outer space and exploration should be conducted "so as to avoid their harmful interference" and where signatory nations have reason to believe that a planned activity or experiment would cause potentially harmful interference with other space activities they should "request consultation" concerning the activity or experiment.
With creative interpretation, the above Articles might be used to support an argument that signatory nations are obliged to avoid the creation of, reduce, and even remove, space debris to allow all States to participate in the exploration and the use of outer space with acceptable risk from debris. However, there are challenges – for example, Article IX does not define what constitutes harmful contamination or what would constitute appropriate measures to mitigate the creation of new debris.
The Liability and Registration Conventions are relevant to the liability of signatory States for damage caused by their space objects.
Article III of the Liability Convention deals with damage that occurs in outer space and makes signatory nations liable to other nations for damage caused by space objects for which they are the "Launching State". Nations are responsible and may be held liable for the commercial activities of their citizen private companies in space, including (arguably) for the consequences and resulting damage of space debris created by those activities. Liability for any and all damage caused by a space object in space attaches upon a finding of fault. This liability arises regardless of when the space object was launched and includes defunct or derelict space objects, with most commentators agreeing that the Liability Convention covers orbital debris.
There are difficulties establishing liability under the Liability Convention. For compensation to be payable, a victim nation must demonstrate proof of fault, causation and damage. The Liability Convention does not define "fault" and it is unclear how this term is applied in practice, nor does it provide assistance on a standard of care for determining fault. It has been argued that the use of "fault" in the Liability Convention was intended to equate to common law negligence, which requires a duty of care and its breach; however, this has not been fully accepted and alternative arguments have been made, for example based on the civil law standard of how "the reasonable man" would have responded under the subject circumstances. Other commentators have advocated for a strict liability system as an alternative to a fault-based system, such as the form of strict liability regime found in the primary international aviation liability agreement, the Montreal Convention 1999.
Proving common law fault generally requires that the wrongdoer fell below a required standard or care. Potentially, for the purposes of the Liability Convention, the requisite standard of care may take into account national and international standards concerning the creation (or mitigation) of space debris or guidelines for conducting space activities, but there is considerable scope for debate concerning the detail of the standards to be applied. Once again, the position is not helped by the lack of mandatory international standards of conduct regarding debris mitigation.
Another obstacle associated with fault-based liability is the difficulty of proving a causal connection between the accident and damage. The most practical problem in establishing liability for damage caused by orbital debris is proving who is responsible for the debris. The Registration Convention seeks to provide information to assist with determining liability by mandating that all "launching States" maintain a register of objects launched into space. Article VI of the Registration Convention directs nations with monitoring or tracking facilities to aid in the identification of space objects that cause damage. However, proving that damage has been caused by space debris may be difficult. It may not be possible to trace the damage to orbital debris or to the owner of the original launched object. Currently, only space debris larger than 10cm is tracked and catalogued. Therefore, the origin of smaller pieces of orbital debris, that cannot be tracked or catalogued by the launching State, is likely to be uncertain.
There is also a question of who has jurisdiction to hear space debris claims and of the law applicable to any such claim in private national law. The Liability Convention only applies to States and each country has authority to make laws regulating various outer space activities by their nationals. Whilst the Liability Convention scheme focuses on diplomatic solutions to address claims caused by a space object, Article XI leaves open the possibility for claims to be brought before the national courts or administrative tribunals or agencies of a Launching State. Article XXIII of the Liability Convention also allows States to enter into their own agreements without interference from the Liability Convention.
The Liability Convention establishes joint and several liability when there is more than one Launching State. The existence of multiple Launching States increases the available jurisdictions for disputes for orbital damage claims to be brought. In the absence of an international convention or other international legal regime providing a clear liability regime for damage caused by orbital debris, national laws will most likely be applied in respect of claims arising from private commercial space activities. For courts unfamiliar with space matters, this can lead to the interpretation of the treaties based on the application of domestic law resulting in a less than uniform treatment of liability. Against this backdrop, the potential for different national laws and legal regimes to apply creates ample opportunity for parties (and their lawyers) to engage in extended argument over which jurisdiction is appropriate and which law should be applied.
In addition to the liability challenges raised, the lack of a clear mechanism for dispute resolution in the Liability Convention and the need to involve signatory nations to bring claims against other nations on behalf of private operators for whom they are responsible has inevitably resulted in the Liability Convention not being commonly used or relied upon. There has yet to be a claim on the basis of damage occurring whilst in orbit. The Liability Convention has not been widely applied, with the only instance arising out of the re-entry of a Russian spacecraft which caused radioactive debris to be scattered on Canadian territory. The claim was settled by diplomatic means.
The possibility of having numerous dispute resolution avenues and applicable laws raises the spectre of uncertainty, and a very significant barrier to enabling wide commercialisation of orbital space. Without an adequate legal international framework addressing the regulation of orbital debris and liability issues, an operator suffering loss in orbit will face very significant issues when seeking to recover compensation for damage caused by orbital debris.
As discussed above, without an adequate legal regime addressing liability and complex issues related to space debris collision, addressing the growing mass of space debris creates ongoing challenges. There is a case for the leading space-faring nations taking the lead in developing international, as well as national, laws and policies on orbital debris. The issue of damage caused by unidentified sources of debris will no doubt remain; that in turn makes it all the more important to establish a legal regime that enforces the protection of this most valuable common heritage of all mankind.
The sustainable future of human activities in outer space demands pro-active action to support long term sustainability of space activities and avoid the real possibility of the Kessler theory coming true. Donald Kessler, retired head of NASA’s orbital debris programme has stated:
"The longer you wait to do this the more expensive it’s going to be. Given the economy, we’ll probably end up putting it off, but that’s really not very wise. This scenario of increasing space debris will play out even if we don’t put anything else in orbit".
The law in this growing area of interest remains untested and unclear and therefore, has the potential to be of great importance to current and future users of space. It is a topic that needs to be watched carefully and clarified for the benefit of all concerned.