A Sky Full of Stars, Constellations, Satellites and More! Legal Issues for a ‘Darkʼ Sky

2.1 Key Elements of International Environmental Law: ‘Applicableʼ to the Sustainable Use of Outer Space?

Article III of the 1967 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies (Outer Space Treaty)²⁰ requires that activities related to the exploration and use of outer space are to be carried out in accordance with international law. It follows that, as a starting point, certain principles of international environmental law might have some application to space activities; however, the extent of application can only be assessed within the context of the unique legal paradigm of space.²¹

In other words, some principles of international environmental law might be of relevance for space activities and be applicable to the space environment, although it will be necessary to take into consideration the specific legal and other characteristics of outer space rather than simply employing a ‘copy-pasteʼ approach.²² We seek here to identify the most relevant environmental law principles that might be applicable for the preservation of the space environment, in particular by taking into account the challenges of mega-constellations, space debris and astronomy observations.

The genesis of contemporary international environmental law can be traced back to the 1972 Stockholm Declaration on the Human Environment,²³ and the 1992 Rio Declaration on Environment and Development.²⁴

Principle 21 of the Stockholm Declaration and Principle 2 of the Rio Declaration assert that States have the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States,²⁵ or to areas beyond national jurisdiction (ABNJ), which include the high seas and outer space. By its legal characterisation, outer space is an area beyond national jurisdiction and thus encompassed by this principle, which some argue represents a norm of customary law,²⁶ and thus may likely also apply to the space environment.

Based on this principle, the duty of control and due diligence in the conduct of space activities, as part of the more general duty of environmental prevention,²⁷ was implicitly recognised by the words of the International Court of Justice (ICJ) in its 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons:²⁸ ‘the existence of a general obligation of States to ensure that activities within their jurisdiction and control respect the environment of other States or of areas beyond national jurisdiction is now part of the corpus of international law relating to the environmentʼ.²⁹

Furthermore, in the 1997 Gabcikovo-Nagymaros case,³⁰ the ICJ noted that ‘in principle, States are under the obligation to ensure that activities within their jurisdiction and control do not cause damage as well as to respect the environment of other States or of areas beyond their jurisdiction and controlʼ.³¹ This so-called ‘prohibition of the causation of transboundary harmʼ may have acquired customary character and may also have relevance for space activities,³² as well as the protection of astronomical observations.

In connection with its statement on environmental protection being an essential interest of States, the ICJ further emphasised ‘the great significance that it attaches to respect for the environmentʼ of areas beyond national control.³³ The ‘no-harm ruleʼ, which many consider to be a principle of customary international law,³⁴ requires State to avoid, limit and mitigate the risk of environmental damage to other States.³⁵ The principle of preventing transboundary harm, set out in the International Law Commissionʼs (ILC) Draft Articles on the Prevention of Transboundary Harm from Hazardous Activities,³⁶ might arguably also have some application to satellite constellation-related activities. These activities are permitted by international law (Article 1 of the Draft Articles) and must be authorised by an appropriate State under Article VI of the Outer Space Treaty. In addition, they are conducted under the jurisdiction and control of a State (Article 2 of the Draft Articles). In this regard, the State of registration of a mega-constellation will have jurisdiction and control over the relevant satellites according to Article VIII of the Outer Space Treaty.³⁷ Accordingly, all necessary steps should be taken to prevent or mitigate damage (Article 3 of the Draft Articles). This provision brings to mind the principle of due regard in space law and Article IX of the Outer Space Treaty, which requires that: ‘… States Parties […] shall conduct all their activities in outer space […] with due regard to the corresponding interests of all other States […]ʼ and shall ‘pursue studies of outer space […] and conduct exploration […] so as to avoid their harmful contamination […]ʼ or ‘cause potentially harmful interference with activities of other Statesʼ.

Furthermore, Principle 19 of the Rio Declaration specifies that: ‘States shall provide prior and timely notification and relevant information to potentially affected States on activities that may have a significant adverse transboundary environmental effect and shall consult with those States at an early stage and in good faithʼ.³⁸ It refers to a system of notification, which is important to avoid harmful contamination of the environment.

This notion is also envisaged in Article IX of the Outer Space Treaty, which deals with the concept that States shall, when conducting space exploration, avoid ‘harmful contaminationʼ of outer space as well as ‘adverse changes to the environment of Earthʼ. Moreover, Article IX provides that State shall adopt appropriate measures and, in particular, shall undertake appropriate international consultations before proceeding with any such activity. These elements are further developed in part 3.

Principle 19 of the Rio Declaration specifically requires a State to notify and consult other States both before and after carrying out any environmentally harmful activities. Such ‘environmental consultationʼ clauses are more specific compared to the general terms under Article IX providing for ‘international consultationʼ.³⁹ The concept of ‘notificationʼ should be detailed with respect to the space environment in order to establish more reliable and appropriate thresholds for its conservation.

When addressing satellite constellation issues, the precautionary principle, set out in Principle 15 of the Rio Declaration, is of possible relevance. The concept implies that, even if the extent of a (environmental) threat is unknown, it is still crucial to take action to eliminate it.⁴⁰ The precautionary principle is the counterpart of the more conventional principle of prevention.⁴¹ ‘Preventionʼ refers to the averting of environmental damage at source through appropriate corrective measures at an early stage.⁴²

Realising the fragility and vulnerability of the space environment,⁴³ as well as the uncertainties associated with the increasing transition to satellite operations through the deployment of satellite constellations, the precautionary principle might potentially be applicable to provide appropriate action and standards for the protection of the space environment.⁴⁴

Certain impacts of large constellations of small satellites on the space environment, and various negative consequences they may have on space activities of other States or entities, including astronomy, are already well documented.⁴⁵ The principles of precaution and prevention are both intended to replace ex post facto corrective measures, which are by definition introduced only when the ecological damage has already occurred, in order to remove or reduce its effects.

Given that the use of such constellations will continue to grow exponentially, we consider it prudent to explore pre-emptive possibilities and adopt measures to reduce the future consequences of mega-constellations on other important activities, including astronomy.

An additional principle of possible relevance may be the ‘concept of common but differentiated responsibilitiesʼ (CBDR)⁴⁶ contained in Principle 7 of the Rio Declaration, which provides that: ‘in view of the different contributions to global environmental degradation, States have common but differentiated responsibilitiesʼ.

This concept is closely related to the notion of sustainable development, which seeks to balance environmental protection and economic development.⁴⁷ It considers that, although all countries have a responsibility for the development of society, including tackling particular (environmental) problems, each has a range of different tools at its disposal.

The Stockholm Declaration points out that: ‘the applicability of standards which are valid for the most advanced countries […] may be inappropriate and of unwarranted social cost for […] developing countriesʼ.⁴⁸ The CBDR approach is intended to take these distinctions into account when targets and benchmarks are applied to global development programmes.

This principle could potentially be of significance in terms of feasible measures to mitigate and remediate space junk⁴⁹ that could conceivably cause interference to astronomical observations.⁵⁰ Indeed, some COPUOS State members have argued that: ‘States most responsible for the creation of space debris and the States having the capability to take action on space debris mitigation should make a greater contribution to space debris mitigation efforts than other Statesʼ.⁵¹

Newer States that have more recently started to undertake space activities face the challenges associated with the environmental degradation of space for which they are not responsible, but nevertheless from which they (like others) are nonetheless potentially adversely affected. One possibility is that those States that have generated space debris make efforts to clean up outer space, through active debris removal and other appropriate means.⁵²

This is, however, a seductive and overly simplistic conclusion. For one thing, the issue remains to determine which State is responsible for causing which and what level of space debris. In addition, the technology to remove space debris largely remains with developed States. More generally, it is by no means clear as to how to ‘encourageʼ those responsible States to actually undertake such activities without providing financial (and other) incentives, as opposed to a ‘stickʼ approach.

Furthermore, concerning the deployment of mega-constellations, it is usually clear which States and operators conduct the activity and, while these have historically predominantly been spacefaring nations, the Rwandan application⁵³ referred to earlier illustrates that the range of space ‘actorsʼ is continually expanding, and easy identification may not always be entirely straightforward. With this in mind, the CBDR principle is highly complex and, in practical terms, may seem inappropriate or not feasible for application to the case of proliferating space debris.

Another element of terrestrial environmental law and sustainable development is the ‘polluter pays principleʼ – the idea that the person or organisation that causes pollution should pay for the damage it causes (or perhaps for the ‘rightʼ to cause such damage).⁵⁴ Principle 16 of the Rio Declaration stresses that: ‘National authorities should endeavour to promote the internalization of environmental costs and the use of economic instruments, taking into account the approach that the polluter should, in principle, bear the cost of pollution, with due regard to the public interest and without distorting international trade and investment.ʼ

In the case of mega-constellations, it will often be relatively easy to identify the launching State(s) and the owner(s) of the constellation; however, it becomes more complicated when space debris is generated. It is difficult, although not always entirely impossible,⁵⁵ to ascertain the ‘originalʼ polluter in the case of space debris – particularly if there are multiple owner/operators of different satellites within a particular constellation, and thus to prove that a specific space object has caused damage to another space object and the space environment. Naturally, this becomes even more difficult if the damage is caused long after the generation of the debris in the first place.

Lastly, the principle of sustainable use is of particular relevance in the case of space activities, including with respect to the use of LEO.⁵⁶ This principle advocates the utilisation of any resource in such a way as to prevent their extinction, as well as the idea of intergenerational equity,⁵⁷ making resources available to all. Accordingly, it requires that resources should be used in a controlled manner.⁵⁸

The application of this principle to outer space is highly valuable in a number of respects, especially in relation to mega-constellation programmes and space debris mitigation and remediation measures. Within this context, the issue of space traffic management is closely connected with the sustainable use of outer space and that, without the development of an effective system of space traffic management through regulation and monitoring, the use of outer space by future generations cannot be assured.⁵⁹

The principles of environmental law considered here can potentially be adapted to the protection of the space environment from the effects of space debris, the growing number of satellites being launched into ‘popularʼ orbits and the adverse impacts on astronomy and associated activities from increasing light pollution. In saying this, however, it bears repeating that a clear determination of the extent to which any of these principles may apply (if at all) to the unique environment of space is not straightforward and must be carefully considered by stakeholders in the adoption of mitigating measures as well as in the development of associated best practices and standards.

2.2 Articles I and IX of the Outer Space Treaty: Free Access to and Use of Outer Space and ‘Due Regardʼ

Principle 2 of the 1963 Declaration of Legal Principles Governing the Activities of States in the Exploration and Use of Outer Space⁶⁰ stipulates that ‘outer space and celestial bodies are free for exploration and use by all States on a basis of equality and in accordance with international lawʼ. This principle in part reflects the terms of Article I of the Outer Space Treaty, which provides that:

the exploration and use of outer space, including the Moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries […]. Outer space, including the Moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies. There shall be freedom of scientific investigation in outer space […]

As noted, the exploration of space can be carried out by astronomers with telescopes, while its physical exploration is conducted by human spaceflight and robotic (and other) space probes. Article I of the Outer Space Treaty can arguably be interpreted so as to implicitly include ground-based astronomy, which may help us to understand how different needs, and the freedoms of exploration and use of outer space, can best be balanced.

Astronomical observations represent an important methodology for accessing, exploring and using outer space. However, the deployment of large constellations of small satellites could have negative consequences for States and others engaged in astronomy as a space exploration activity. Hence, an appropriate coordination and balance must be found between astronomical observation and satellite activities that, at the same time, might allow for economic and developmental benefits for States and operators to accrue, while not unduly interfering with other equally important space activities.⁶¹

Article I must be reconciled with Article IX of the Outer Space Treaty, which demonstrates that the exploration and use of space is not completely unfettered – such activities must be undertaken within important behavioural requirements. In other words, the principle of freedom of exploration and use of outer space must also take account of, inter alia, the imperative to preserve the space environment.

The concept of cooperation, mutual assistance, avoiding harmful interference, and consultations – essential elements within the terms of Article IX – had been previously articulated in Principle 6 of the 1963 Declaration of Legal Principles referred to above.

Article IX requires that, in the exploration and use of outer space, States Parties to the Treaty shall be guided by ‘the principle of cooperation and mutual assistanceʼ and shall conduct their activities ‘with due regard to the corresponding interests of all otherʼ States Parties. In addition, they shall ‘pursue studies of outer spaceʼ and conduct their activities so as to avoid ‘harmful contaminationʼ of the space environment.

The final element of the provision requires States to engage in ‘appropriate international consultationsʼ if they have reason to believe that their proposed space activity would cause ‘potentially harmful interferenceʼ to the activities of other States, and also gives the opportunity for other States to request such consultations regarding planned activities by another State if they have reason to believe that those activities will have such a potential impact. This appears relevant in the case of the (potential) impact of mega-constellations on astronomy observation and, if this is the case, would require that consultations be conducted between the parties involved in appropriate circumstances.

As noted, in certain respects, Article IX represents a limit to the freedom of exploration and use of outer space. States are required to consider whether and how the exercise of their own rights and freedoms impact on the space activities of other nations. Thus, space activities carried out by a given State should reflect not only its own interests but take account of the ‘correspondingʼ interests and rights of the other States Parties to the Outer Space Treaty.⁶²

In addition, Article IX refers to the principle of ‘due regardʼ,⁶³ which implies that States, and private entities authorised by their respective State, should carry on space activities with a certain standard of care, attention, or observance. This idea of due regard is also referred to (albeit in a very different context) in the 1982 United Nations Convention on the Law of the Sea (UNCLOS) in Article 87(2), which states: ‘These freedoms [of the high seas] shall be exercised by all States with due regard for the interests of other States in their exercise of the freedom of the high seas, and also with due regard for the rights under this Convention with respect to activities in the Areaʼ.⁶⁴

Both the high seas and outer space are, as noted, regarded at law as being beyond national jurisdiction and are often thought of as belonging to the category of res communes omnium⁶⁵ which, while prohibiting national appropriation, recognises the right to use and exploit these areas and their resources with due diligence, by taking into account the interests and rights of other States when they conduct activities in those areas. Article IX appears to introduce an objective ‘due diligenceʼ concept within the particular circumstances. Due diligence typically requires the taking of all reasonable and appropriate measures that might be expected in order to examine and evaluate the risks that may affect a specific situation, so as to appropriately address them.

As noted, Article IX also deals with the notion of ‘harmful contaminationʼ. The provision implies that any contamination which would result in harm to another Stateʼs programmes is to be avoided. However, Article IX does not specify under what circumstances it would be necessary to adopt appropriate measures, or indeed which measures would in fact be appropriate. Nevertheless, one can argue that the obligation to take all appropriate measures to prevent harm, or to minimise the risk, would apply to existing as well as ‘possible futureʼ activities that might involve such a risk.

Article IX deals as well with mechanisms of consultation with regard to the avoidance of potentially harmful interference in outer space. As noted, a State (or its nationals) that plans an activity or experiment has the obligation, before proceeding, to undertake appropriate international consultations with other States Parties if it has reason to believe that such activity or experiment would cause potentially harmful interference to the activities of those other States in the peaceful exploration and use of outer space.⁶⁶

In this context, one could argue that operators should, in appropriate circumstances, be required to enter into consultations with the relevant astronomers before deploying a mega-constellation programme (assuming that their reasonable investigations would enable them to be made aware of those astronomical activities).⁶⁷ Such consultations should be undertaken at an international level given the environmental and technical issues raised.

In addition, a State potentially affected by an activity to be conducted by another State may request that the latter enter into consultations regarding that specific mission/activity. In this regard at least, consultation could be viewed in part as an element in a more effective environmental protection regime for outer space.⁶⁸ However, it should be noted that, in relevant circumstances, the proposed activity might have already been authorised by an appropriate State (as required by Article VI of the Outer Space Treaty) and conducted by a private entity, while the activities of amateur astronomers do not require such authorisation.⁶⁹ Coordination and information sharing is therefore a paramount requirement.

To sum up these observations, States Parties to the Outer Space Treaty have to: (1) conduct their space activities with due regard to the corresponding interests of all other States Parties to the Treaty; (2) carry out their activities in outer space in a way that avoids harmful interference with the missions of others; and (3) engage in international consultations when necessary and required. Moreover, it can be argued that Article IX could, in appropriate circumstances, apply with respect to terrestrial activities such as ground-based astronomy that are potentially affected by mega-constellations and other activities conducted in outer space. That said, this provision has never been applied to cover such a contingency.

Nevertheless, even if Article IX provides some relevance for safeguarding the space environment,⁷⁰ it lacks precision,⁷¹ in particular concerning the terms ‘appropriate measuresʼ and ‘harmful contaminationʼ, and also with regard to the scope of its application.

3.1 Environmental Impact Assessment in Areas Beyond National Jurisdiction: the Case of the High Seas

Principle 17 of the Rio Declaration emphasises that: ‘Environmental impact assessment, as a national instrument, shall be undertaken for proposed activities that are likely to have a significant adverse impact on the environment and are subject to a decision of a competent national authorityʼ.

While the Rio Declaration is a non-binding instrument,⁷² many countries have included environmental impact assessment (EIA) requirements within their national environmental law frameworks.⁷³ International obligations to carry out EIAs also exist in relation to activities that take place in areas beyond national jurisdiction.⁷⁴ Such obligations can be identified in the 1991 Protocol to the Antarctic Treaty on Environmental Protection,⁷⁵ and the 1982 UNCLOS.⁷⁶ In the 1997 Gabcikovo-Nagymaros case, the ICJ held that there was a duty to conduct EIAs before proceeding with serious transboundary projects.⁷⁷

The starting point for an EIA is the idea that the impact of (potentially) environmentally harmful projects should be analysed before the authorisation of the project, in order to be able to take an appropriate decision given all possible (reasonably foreseeable, identifiable and measurable) impacts of that project.⁷⁸ In this sense, an EIA is in some ways a practical application of the precautionary principle in order to as much as possible prevent environmental harm, since it is necessary to understand the environmental impacts of a project as early as possible. A precautionary approach is desirable where the long-term effects are little known, and those effects will also emerge cumulatively with other ongoing changes in large-scale ecosystems.

If one considers general State practice in relation to the high seas, scientists continue to make important discoveries about marine depths in locations that are ABNJ, which are in most cases distant places that support life throughout the global oceans and are home to some of its most fascinating and valuable species. With new and emerging activities threatening the health of these ecosystems, safeguarding their biodiversity is increasingly important.

To ensure that they do not upset the fragile and interconnected marine environment,⁷⁹ the conduct of high seas activities and any associated impacts must be fully understood and carefully managed, and an EIA is a significantly important tool in this effort.⁸⁰ EIAs allow policymakers to identify the potential effects of proposed projects, explore alternative solutions, and determine ways to prevent, mitigate and control environmental harm.

United Nations General Assembly Resolution 69/292 underlines the fact that States should commit to developing an: ‘international legally binding instrument … on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdictionʼ.⁸¹ After years of discussions by States at the United Nations, the final text of the instrument (‘Agreement under the United Nations Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdictionʼ (BBNJ))⁸² contains provisions addressing the issues relating to EIAs.

UNCLOS establishes the mandate of the International Seabed Authority (ISA) to: ‘organise and control activities in the Area, particularly with a view to administering the resources of the Area.ʼ ‘The Areaʼ refers to the seabed beyond the 200 nautical mile limits of national jurisdiction. UNCLOS requires that the ISA manage potential mineral-related activities of the Area for the benefit of humankind as a whole – where both the Area and its resources are considered ‘the common heritage of [hu]mankindʼ.⁸³

Central to the mission of the ISA is the ‘effective protection of the marine environmentʼ and management that allows development of the Areaʼs resources to contribute ‘to agreed international objectives and principles, including the Sustainable Development Goals (SDGs)ʼ.⁸⁴ While the ISA does not govern seabed mining within any nationsʼ exclusive economic zones (EEZs), deep-water mineral extraction is also being pursued in these areas. Management here is likely to reflect the progression of what might be developed and implemented by the ISA. The evolution of this is being carefully watched.

The ISA is currently developing regulations for commercial-scale deep-seabed mining: ‘The Mining Codeʼ. This relates to both exploration and exploitation of minerals.⁸⁵ These regulations are necessary in order to meet the mandate of the ISA to protect the marine environment.

In 2019, the ISA began to hold consultations on a series of draft ‘Standards and Guidelinesʼ⁸⁶ which set out how impact assessment of deep-sea mining projects should be undertaken, in particular for EIAs. The documents are a component of the Mining Code (exploration and exploitation) and are intended to operationalise the exploitation regulations and outline the process and criteria by which projects will be appraised for acceptability and granted permission.

These standards aim to ensure that EIAs for activities in the Area are designed with a view to protecting and conserving the marine environment; to anticipate and avoid or minimise harmful the environmental effects of exploitation activities; and to ensure that environmental considerations are expressly addressed and incorporated into the ISA decision-making process.

While application by analogy is not appropriate, certainly some of these elements could be take into consideration within the context of deployment of mega-constellations and its impact on astronomy, perhaps in terms of a ‘Space Codeʼ, comprised of appropriate standards and guidelines. Moreover, one idea is that the Secretariat of COPUOS, the United Nations Office for Outer Space Affairs (UNOOSA), could be given a mandate related to the preservation of the space environment, given the impacts that mega-constellations and space debris have on environment and other space activities.

3.2 A Sustainable Impact Assessment for Space Activities

The concept of an EIA is not a well-established tool in the international law of outer space. However, the negative effects of some space activities are well known, including the potential ‘overcrowdingʼ through a proliferation of mega-constellations and the creation of space debris on the space environment, both of which also have consequences for astronomy.

This gives rise to the question as to whether there exists an obligation on (authorising) States to conduct EIAs on potential space activities,⁸⁷ including possibly a strategic environmental assessment (SEA)⁸⁸ and a sustainability impact assessment (SIA), in order to minimise light pollution and protect the dark and quiet skies before such authorisation.

An SIA could be particularly relevant for space activities in that it may increase awareness of the potential for developing more sustainable policies, strategies and action plans.⁸⁹ As regards large constellations of small satellites and their impact on astronomy, performing an SIA would be a major refinement to an EIA and would, for instance, cover the key elements of the 2019 Guidelines for the Long-Term Sustainability of Space Activities (LTS Guidelines).⁹⁰ This might include the implementation of policies that support the objectives of minimising the impacts of human activities on Earth as well as on the outer space environment (Guideline A.2), and the adoption of appropriate safety measures to protect the Earth and the space environment from harmful contamination (Guidelines A.4 and D.1).

An SIA could be required of private entities⁹¹ and contractors as a pre-condition to obtaining a licence from the appropriate State. They would have to comply with any standards and rules encompassed in the assessment along with any other conditions included with the licence approval.

4.1 Developing and Implementing a Set of Technical and Regulatory Provisions to Promote Safe Access to Outer Space

As noted, the number of satellites in orbit, and particularly in LEO, continues to increase, and the instances of close approaches requiring coordination between operators are growing.⁹² In this context of ever-expanding space activities, it is becoming an imperative to devise appropriate and effective rules for Space Traffic Management (STM).⁹³

According to the International Academy of Astronautics (IAA), STM represents: ‘the set of technical and regulatory provisions for promoting safe access into outer space operations in outer space, and return from outer space to Earth free from physical or radio-frequency interferenceʼ.⁹⁴ With the advent of numerous non-governmental entities into the realm of space activities, the positioning of mega-constellations, the increase of space debris,⁹⁵ and the growing number of launch vehicles, appropriate ‘rules of the roadʼ are necessary in order to ensure the safety and security of space operations and to preserve the long-term sustainability of space activities.⁹⁶

Space Traffic Management is most likely relevant throughout all elements of a typical mission – during the launch, in-orbit operation and re-entry phases. The United Nations Space Treaties provide for some significant frameworks relevant for the future establishment of a more comprehensive STM regime, such as the registration of space objects, and requirements for notification and consultations. A comprehensive STM system should also relate to the terms of Article IX of the Outer Space Treaty, which (as noted above) provides an obligation on all States Parties to pay due regard to the corresponding interests of other States Parties and to act so as to avoid potential harmful interference to the activities carried out by other States in outer space.

Notwithstanding this, the provisions of the United Nations Space Treaties alone are not sufficiently comprehensive to meet the challenges of new space activities without additional augmentation.⁹⁷ The myriad issues raised by the increasing proliferation of mega-constellations and of orbital space debris highlight even more the impacts for astronomical observations, thus meaning that an effective STM system becomes ever more urgent.

The issue of STM was added as a new single item to the agenda of the Legal Subcommittee of COPUOS in 2016 under the title ‘General exchange of views on the legal aspects of space traffic managementʼ,⁹⁸ but no concrete results have as yet been formulated. However, some relevant elements are present in ‘soft lawʼ documents, such as the 2019 LTS Guidelines, which provide practical approaches for pre-launch conjunction assessment and the promotion of collection, sharing and dissemination of space debris monitoring information. There is a necessity to disseminate such data also with astronomical requirements.

Some crucial elements of STM can also be identified within national space legislation, policy, regulations and licensing regimes.⁹⁹ Nevertheless, these national frameworks deal primarily with issues related to the preservation of the space environment, the mitigation of space debris, and safe launches. In addition, States like Australia and South Africa are, as noted above, now adopting policies and strategies that include issues relating to astronomy and the preservation of space environment.¹⁰⁰

The way forward for effective STM necessitates technical coordination and cooperation between the relevant actors involved. Developing an STM system capable of effectively and comprehensively managing launches, in-orbit operations, and re-entries will require practical adherence to important principles of cooperation, mutual assistance, due regard, the duty to consult, and notification.

A probable first step is to incorporate these rules into national space regulations and licensing regimes.¹⁰¹ Another option is to develop an informative platform within the United Nations as a mechanism for integrating the efforts of States, international intergovernmental organisations, spacecraft operators and specialised national and international non-governmental organisations in the collection, systematisation and provision for general use and analysis of information on objects and events in outer space.¹⁰²

In 2021, during the sixtieth session of the COPUOS Legal Subcommittee session and the fifty-eighth session of the COPUOS Scientific and Technical Subcommittee, the impact of large satellite constellations on radioastronomy and optical astronomy was underscored, as well as the necessity to identify STM standards that would generate mutual benefits. This was important in particular in view of the increasingly complex and congested space environment resulting from the growing number of objects in outer space, the diversity of actors in outer space and the increased number of space activities, which each pose a challenge to the safety and sustainability of space activities.¹⁰³

In that connection, there were calls to keep dark and quiet skies for science and society,¹⁰⁴ in particular regarding non-geostationary orbit satellites.¹⁰⁵

Space Traffic Management could be considered with a view to developing and implementing a set of technical and regulatory provisions to promote safe access to outer space, the safety of operations in outer space, and safe return from outer space, free from physical or radio frequency interference. Hence, both legal and technical aspects of STM should be developed. The international community must strive towards a legally binding instrument for STM negotiated under the aegis of the United Nations, and both private and public stakeholders should be included in the development of any related strategies and regulatory frameworks.¹⁰⁶

The growing use and development of large constellations of small satellites, if anything adds to this imperative to implement comprehensive STM measures.¹⁰⁷ The increasing deployment of satellite constellations will lead to Earthʼs orbits becoming more crowded in the coming years.

Space Traffic Management encompasses safety issues that require international coordination and harmonised rules. In June 2022, European Ministers responsible for space adopted a set of conclusions related to STM.¹⁰⁸ The conclusions strengthen the EUʼs common position on STM and underline the necessity of sharing capacities, information and best practices amongst Member States in order to address strategic and competitiveness challenges in space. The Ministers underscored the importance of strengthening EU space surveillance and tracking capabilities, and of coordinating legislation and standardisation of governance requirements.

As large constellations of satellites pose a heightened risk for the safety and sustainability of space activities, in particular with regard to the mitigation of space debris, and present challenges for astronomical observation, a comprehensive STM system could enhance the safe and sustainable conduct of space activities.¹⁰⁹ There is a need to manage the orbital environment with appropriate standards and best practices for the maintenance and stability of the satellite industry, and also to pay proper account to the importance of astronomical observations for humanity.

4.2 Radio-Quiet Skies: STM and ITU Coordination

By the 2030s, if one adopts a ‘business-as-usualʼ case, more than 5,000 satellites could potentially be sighted above the horizon at any given moment in the case of a typical mid-latitude observatory.¹¹⁰ Of those, thousands could be illuminated, and thus affect all-optical wide-field images obtained at twilight, perhaps with the exception of those taken by the smallest optical telescopes.¹¹¹

Large constellations of satellites also pose a challenge to radio astronomy.¹¹² Though certain narrow frequency bands are protected by the International Telecommunication Union (ITU), and some telescopes are located in protected radio-quiet zones,¹¹³ the sheer number of new satellites will result in thousands of additional radio transmitters moving rapidly across the sky. These are bound to affect measurements made by highly sensitive radio telescopes. With this in mind, the establishment of STM rules will need to be carefully coordinated with ITU requirements.¹¹⁴