1 Introduction: Accelerating to the Moon

The global space economy has been in full expansion for a few years [76, 77, 79] with all the segments growing at a steady pace. The forecast for 2026 shows further record investments in space technology, going even beyond the 2025 private investment (+ 48% to $12.4 billion, of which $3.8 billion only in the final quarter; 93). And while a clear estimate of the global space economy value can be elusive [33, 80, 84, 7, 75] there is little doubt that the sector, now over the US $ 600 billion, is on track to exceed the landmark US$1.8 trillion by 2035 predicted by JP Morgan a few years ago [106].

Compared to these numbers, the cislunar economy is a far smaller [around US $ 12 billion; 2, 18; 92], infrastructure-led system, sitting now at the edge of the sector, together with other high-risk, long-term return segments like suborbital tourism and space mining. Some estimates [99, 109] offers a snapshot of infrastructure market dominated by few big players, a projected growth of approximately $170 billion by 2040, part of which will be coming from in-situ space resources utilisation (ISRU), mainly on the lunar soil. The rest of the revenue will be coming from lunar transportation, estimated to grow up to around $100 billion, the biggest share in terms of contribution and lunar data market [which include both telemetry and environmental data of various kind; 99].

These are comparatively tiny numbers; and yet, the interest in the area keeps growing from national space agencies, governments and commercial operators alike [9, 17, 25, 45]. And if NASA and the USA are on the lead with the Artemis programme and the return-to-the-Moon before-2030 timeline, they are by no mean the only ones with a well-planned lunar agenda.

Over the next decade, the cislunar region is expected to host more than 30 missions, many carrying multiple payloads and experiments. ESA, the European Space Agency, is a major partner in NASA’s Lunar Gateway, which is going to be the first international space station in orbit around the Moon in support the Artemis programme, contributing habitats (Lunar I-Hab [70]) logistical support (Lunar View) and telecommunication systems [Lunar Link; 33].

Among the other frontrunners, there are countries already experienced about missions on the lunar soil, such as India [57], Japan, South Korea, the UAE, and Israel. China, in particular, has established itself as a leading actor with the Chang’e missions [58, 83], which returned the first far-side lunar sample return to Earth in June 2024 and with a crewed lunar landing by 2030 in the plan [59].

Moreover, China and Russia (another country with a longstanding record of lunar missions) are jointly developing the International Lunar Research Station near the lunar South Pole [24], reflecting an ongoing, and quickly intensifying, geopolitical competition on the space sector on Earth.

2025 marked in this sense important changes at a world level, starting with a more prominent influence of defence on space investments and more in general a global shift towards space sovereignty [72]. This is leading, in Europe among other places, to the consolidation of the sector toward ‘national champions’, with countries trying to acquire and control space capabilities across the entire value chain.Footnote 1

But all this flurry of activities, current and prospective, comes with a series of uncertainties, concerns, and unsolved questions on the modalities this second phase is going to unfold, questions that are both conceptual and eminently operational.

First of all, it is the viability/feasibility of the overall effort. Like many segments of the space industry [first of all, space tourism; 86, 46] there are important concerns related to sustainability [94, 98, 78], which resonates with the wider, ongoing debate of space sustainability as a whole as a priority for the global space sector [12, 62, 90, 101].

However, in the specific perspective of cislunar region, these concerns are strongly (and certainly more directly) related to the overall security discourse, due to the already mentioned geopolitics aspects [79, 90].95]; 96 Environmental security, while traditionally grounded in terrestrial ecosystems, will have therefore to be discussed and somehow reframed to serve as a conceptual framework for cislunar sustainability. Section two covers this specific aspect, examining how the two dimensions of environmental security and sustainability may well overlap to some extent but still remain, or so they should, conceptually distinct in outer space, and specifically in cislunar space.

This leads to Sect. 3, which tackles a fundamental and complex issue in cislunar space: defining the extent of its boundaries. A definition that is as much as technical and astronomical (focused on gravitational spheres of influence, Lagrange points, and orbital mechanics) as it is economic and geopolitical (prioritising resource extraction zones, orbital infrastructure, and logistical corridors) and that leads to competing and mismatching boundaries even inside the same national space (the US is a case in point). These boundary constructions shape how risks are perceived and managed, determining whether cislunar space is treated as a neutral physical domain or as an emerging arena of economic competition and strategic vulnerability.

Section 4 explores instead another key point: how this unevenly defined cislunar space is exposed to a composite, three-dimensional risk environment [23, 49], in a perspective that is both shaped by security issues and sustainability challenges. Physical risks include radio frequency congestion, debris propagation, and radiation exposure; economic risks arise from infrastructure fragility, monopolisation of strategic orbital points, and unequal access to resources; while geopolitical and security risks derive from dual-use technologies, escalation dynamics, and the absence of shared situational awareness [8, 44].

Managing these overlapping threats [48, 108] requires an integrated risk assessment approach that mirrors environmental security models on Earth but adapts them to non-terrestrial dynamics, keeping into a more prominent consideration the security aspects compared to the more general and overarching sustainability discourse. This enables a more accurate threat identification and mapping and offer both scenario analysis in terms of severity and mitigation strategy. The outcomes are discussed in Sect. 5, together with some limitations.

Such an approach, however, is constrained by a characteristic and probably inevitable at these early stages, governance deficit, which, while still existing in Earth’s orbits, is particularly acute in cislunar space. This because existing precedents, largely developed for low Earth orbit, are painfully insufficient in outer space due to differences in scale, permanence of infrastructure, and strategic value. A viable way forward lies in developing a cislunar governance framework that combines environmental security principles, shared risk monitoring, and enforceable norms for sustainable use [50,53, 54, 60].

As argued in the conclusions, in Sect. 6, treating cislunar space through an environmental security lens offers a coherent pathway to balancing exploration, exploitation, and long-term stability, provided governance mechanisms evolve in step with technological and economic expansion.

2 (Contested) Conceptual Dimensions: Environmental Security as a Framework for Cislunar Sustainability

If it’s true that at the onset of the space age in 1957 space and security were intertwined in terms of aims, means, and modalities [88], 70 years later, the security dimension still plays an important role in the space sector, the growing relevance of the so-called commercial space nonetheless. Moreover, even the typical realist approach to security is applicable, and applied in outer space, especially with the renewed geopolitical friction highlighted in the previous section. Dolman is not alone in declaring that the “geopolitical theory developed for the Earth and its geographical setting can be transferred to outer space” with the “strategic application of new and emerging technologies within a framework of geographic, topographic, and positional knowledge,” [30:6].

However, to correctly frame the security discourse in space it is necessary to elaborate on how the concept of space security expanded 82] from what was an original “two-dimensional model of military and environmental dimensions of space security,”[97:4] to a more complex and multifaceted definition that does not only include only non-state actors, e.g., private operators, but also non-traditional kind of threats originating in space, both man-made (debris) and not, such as space weather, space contamination and asteroids among them.

Otherwise said, we need to engage with a non-traditional, less realist approach of security, among which the environmental component was about the first to historically emerge in the debate [20, 29, 61]

As such, environmental security addresses threats that arising from the environment rather than from direct military aggressions. Although there is a variety of causes identified in the literature, it often revolves around the concept of scarcity and the access to vital resources (e.g., in resource wars; [61). But there are also other causes that can provoke a securitization of the environment. When for instance resources are depleted or degraded, the securitization actor (generally the state) can frame this environmental degradation as security threat (not just technical problem) triggering emergency measures [10, 19, 32] which, in certain conditions, increase the likelihood of conflicts.

Though often used interchangeably, ‘Environmental Security’ and ‘Sustainability’ are fundamentally different concepts and treating them as the same is a dangerous oversimplification. While they overlap on issues like climate change, their core questions, solutions, and political consequences diverge sharply.

Environmental Security adopts a security studies lens, asking how environmental change threatens the state, national interests, and political stability. It is inherently anthropocentric, viewing nature as a source of risk to be managed and focusing on acute threats like resource wars, climate-induced migration, and conflict. This type of framing risks, however, ‘securitisation’, in which environmental challenges are met with militarised responses, border fortifications, and authoritarian policies, rather than international cooperation.

Sustainability, which, instead of development and environmental science, is based more on possible/viable ways to meet our present needs without compromising their future availability. It tries to identify a trade-off between economic returns, social needs, and environmental health, at times questioning the ethics behind strategic decisions or industry objectives (e.g., in the already discussed case of space tourism; 86). Sustainability, even in its more ‘technically’ oriented definitions like in ESA’s definition of ‘space sustainability’ [112], combines managing present threats to existing systems with questioning whether that system should work in that way in the first place without endangering the future generations.

In the current discourse, the two dimensions are, more often than not, conflated in one, and this is the case of the recent debate on space sustainability (more about that later on).

The ‘securitisation’ of space is therefore a rather typical case of a realist IR approach [30, 28], where debris crisis is seen (rightly so) more as a by-product of security threats on Earth than a result of economic externalities.

Some authors evaluate this (partial) overlap in a positive way. For instance, Floyd believes that securitisation perspectives do offer a powerful analytical tool for some urgent environmental security issues, such as climate change, offering a neutral framework ground. “A securitisation lens helps researchers understand how climate change becomes seen as a security threat and also that climate security takes different forms with actors prioritizing different threat narratives, referent objects, and providers of security,” [39, 35].

Conflating the two dimensions might well lead, however, to dangerous outcomes.

This approach can prioritise short-term, state-centric stability over long-term, systemic justice.

An example here is the migration flows resulting from climate change, which are addressed focusing on the symptoms (e.g., the illegal migrants) instead of mitigating the structural causes (global inequality, fossil-fuel dependency, collapsing on the international bodies/treaties limiting emissions, and so on).

Most importantly, and worryingly, framing the environment through a security lens encourages. the nation states to act in self-interest, prioritising national security over global cooperation. This competitive logic undermines the collaborative frameworks essential for protecting shared “commons.”

By viewing resources as threats to be managed rather than a collective responsibility, securitisation risks damaging the very international stewardship needed for long-term, sustainable solutions.

Applying these concepts to outer space reveals that the domain is facing increasing challenges 96, 97], as self-interested actions by independent actors deplete shared, limited resources because no single entity owns or regulates them. There is, as a matter of fact, a growing literature on this subject, which addresses the management of Earth’s orbits, a so-called Area Beyond National Jurisdiction (ABNJ) prone, as the much as others, to the “tragedy of the commons” due to self-interested behaviours and a lack of ownership mechanisms [31, 40, 41, 47, 88, 103].

The debate about environmental security in space has been recently reinterpreted in terms of sustainability, and a lot of discussions, both in the industry and in academia, are ongoing to understand how the space sector could keep growing at this pace in a way that is both equitable and sustainable in the long-medium term[107].

The challenge in this case comes from another perspective: even the agreed definition of the concept ‘space sustainability’ is hard to come by, let alone its implementation.

Multiple definitions exist, often overlapping but lacking unified metrics.

One of the most commonly adopted is the one from the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS) which defines it as “the ability to conduct space activities indefinitely into the future, ensuring equitable access to the benefits of space exploration and use for peaceful purposes, while preserving the outer space environment for future generations.” [100].

In comparison, the definitions from the major space agencies often emphasise technical responsibility over the UNCOPUOS philosophical principles.

The European Space Agency (ESA) focuses on responsible use to ensure future service availability, explicitly mentioning debris management, collision prevention, and minimizing environmental impact. NASA’s definition aligns closely, centring on preserving the environment through debris mitigation, best practices, and international collaboration. The UK Space Agency similarly prioritises minimising debris creation and avoiding harmful interference.Footnote 2

A more ambitious framework is proposed instead by the Scottish Space Agency, which divides the concept into three pillars: sustainability in space (environmental friendliness of space activities), for space (sustainable technologies), and from space (using space data to support the Earth’s environment).

The significant limit of these definitions is the lack of agreed metrics and targets, such as defining clear limits in terms of number satellites in specific orbits or setting regulatory measures for emission controls in stratosphere.

While technical guidelines do exist, such as the Inter-Agency Space Debris Coordination Committee (IADC) recommendation for satellites to de-orbit within 25 years of their end-of-life [12] for GEO and NASA’s five years in LEO [69], these are best practices rather than binding laws.

The regulatory framework underpinning these efforts relies, with little changes, on the Five UN Treaties from the 1960s and 1970s [68], particularly the Outer Space Treaty (OST), which designate space as the "province of all mankind".Footnote 3

This framework is increasingly considered outdated and inadequate, for obvious reasons.

The rise of objects in space, such as satellites, space stations, and non-operational objects like space junk and debris, has increased rapidly due to the commercialisation of space and the expansion of private companies in the worldwide space sector (not just the EU or the US). With 80 + countries now sending their satellites into orbit [33], the probability of a cascading chain of collisions due to the debris crisis has increased, commonly known as a Kessler Syndrome [12, 62], and poses potential catastrophic environmental and economic consequences.Footnote 4

The current governance structure struggles to address critical issues like the debris crisis and necessitating a radical rewriting of international regulations to ensure long-term viability.

In addition to that, regulatory cohesion is also challenged by competing national visions, and the emerging national legislations that regulates selected aspects of the space activities, at times clashing, explicitly or not, with the existing regulatory framework.

However, the most controversial and significant piece of national regulation detailed in the sources is the US Executive Order (EO) 13,914, issued in 2020, explicitly rejects the notion of outer space as a “global commons,” challenging the historical understanding of the UN treaties.Footnote 5 his national measure challenges the historical understanding of the UN Treaties.

While the measure applies only at the national level without binding international effects, it sets a significant precedent by removing the "constraining concept" of global commons [85], thereby potentially complicating efforts to achieve equitable resource exploitation and sustainable growth. This move is seen as steering the regulatory framework in a contrary direction to the "province of all mankind" ethos established by the 1967 Outer Space Treaty.

While the measure solely applies at the national level and lacks international binding effects, it originates from the leading country in the space sector and sets a significant and noteworthy precedent. This situation presents a significant obstacle to achieving both equitable resource exploitation and a sustainable responsible growth.

Another US Orbital Debris Mitigation Standard Practices (ODMSP) established in 2001, the Orbital Debris Mitigation Standard Practices (ODMSP) serve as a framework for addressing the increase of orbital debris in near-Earth space. Limitations: While these practices provide a structure for mitigation, the sources note they were not designed for operations beyond the geosynchronous orbit (GEO). As human activity extends toward the Moon, there is an urgent need to update these practices to cover cislunar space effectively.

And this is where the next, formidable challenge starts.

3 Boundaries of Cislunar space: An Elusive Security Object?

Any research aiming at discussing in detail the sustainability challenges that the exploitation of the cislunar space faces has to clear an important roadblock first: defining what the cislunar space is in the first place.

If anything, because even the extent of this domain can vary according to the different agencies and interest group, and this alone is part of the challenges.

What is commonly intended as ‘cislunar space’ includes that region of outer space beyond Earth’s geosynchronous orbit (XGEO; [25]). In distance terms, it starts after 36,000 kms from the surface of the Earth (the GEO border) and it extends slightly after the Moon’s orbit (the Moon is on average 384,400 kms away from the Earth).

Otherwise said, it is a huge three-dimensional region, defined by the gravitational influence of both the Earth and the Moon [91], not by exact coordinates.

The working NASA’s definition [14] is spelt in a slightly different way, covering overall the same areas but in a more extended version. It includes the Earth’s orbits (LEO, GEO, HEO) and even LLO (lower lunar orbit).

However, the US policymakers adopt a different one.

In the 2022 National Cislunar Science & Technology Strategy (NCSTS). “Cislunar space is the three-dimensional volume of space beyond Earth’s geosynchronous orbit that is mainly under the gravitational influence of Earth and/or the Moon. Cislunar space includes the Earth-Moon Lagrange point regions, trajectories utilizing those regions, and the lunar surface,” [74:3].

This mismatch in definition, only a matter of astrophysics until now, is going to create governance problems down the line, if anything, for the complexities linked to the identification of the applicable regulatory framework, existing in the case of Earth’s orbits and virtually absent in cislunar space.

This will be especially relevant for what concerns measures of SSA (Space Situational Awareness), debris management and even RF (radio frequency) allocations. And if 2022 NCSTS definition is clearly more interested in the definition and utilisation of cislunar resources, hence the specific and narrower focus, the fact that it comes from the same space player (US) that elsewhere defines it differently and more broadly (NASA) creates dangerous ambiguities, which will be discussed in their specific implications in the following sections.

Figure 1 illustrates also another important aspect in the definition of cislunar space in functional and operational terms, and namely, the identification of areas of strategic interest in it: the Earth–Moon Lagrange points (generally called EMLs), about which much has been written.Footnote 6

Fig. 1
Fig. 1
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source: Author’s elaboration on Creative Common Licence Image

The cislunar space

Cislunar space is regarded as a single, continuous region encompassing the entire gravitational domain of the Earth–Moon system, extending from high Earth orbit through lunar orbit and associated transfer trajectories. It represents an enormous operational volume used for transit, orbital operations, and sustained space activities.

Within this region, the Earth–Moon Lagrange points (L1–L5) are mapped as discrete, mathematically defined locations where gravitational and inertial forces are in equilibrium.

The Earth-Moon system, like any other two-body system in space, contains five such points: L1, L2, and L3 constitute unstable equilibrium locations requiring continuous correction, while L4 and L5 form conditionally stable regions positioned 60 degrees ahead of and behind the Moon in its orbital path.

These points are highly localised relative to the scale of cislunar space and are not physical “places” in the conventional sense, which is a common misconception.

They are not, otherwise said, ‘fixed parking spaces’ but rather gravitational "harbours" around which spacecraft execute complex periodic trajectories in their vicinity, e.g., halo orbits, Lyapunov orbits, and Near-Rectilinear Halo Orbits (NRHO), all maintained through active station-keeping manoeuvres, and traversing extended three-dimensional trajectories that can span tens of thousands of kilometers.

These areas are huge by any standard and it defies intuitive understanding.

L1, situated approximately 320,000 km from Earth (85% of the Earth-Moon distance), and L2, positioned on the lunar farside, each anchor orbital families extending across volumes measuring trillions of cubic kilometers.

This vast spatial availability creates a critical paradox: Lagrange points feel congested not because physical space is scarce, but because functional value is concentrated and everything, including the physics of radio frequency spectrum, does function in a very different way compared to what we are used to know.

Otherwise said, Lagrange points are functionally valuable not because of spatial scarcity (not the case), but because they enable strategically advantageous positioning for communications relay, observation, and system coordination. This distinction clarifies why operational, spectrum, and governance challenges tend to concentrate at Lagrange points despite the vast physical volume of cislunar space as a whole.

The implications of all this are explained and discussed in the next section.

Here is the case to note one final point: cislunar space comes with a series of unique complexities for human missions. While it is legally governed by general outer space law, it is in practice operationally ungoverned, given that the existing space governance frameworks assume conditions like the ones existing in LEO/GEO.

Cislunar space breaks all those assumptions.

Legally, most space governance frameworks assume physical congestion (like GEO slots).

There are, in the present conditions, no orbital filing system for Lagrange orbits, no cislunar traffic management authority, no spectrum coordination regime tailored to deep-space environments (ITU spectrum rules are Earth-centric, and obviously no whatever debris management policy in place.

In these conditions, the risks of conducting cislunar operations look like driving blind on an unknown road.

And this is where we need to begin.

4 A Composite Risk Assessment in Cislunar Space: managing three-dimensional threats

From orbital conditions to handling of radio frequencies to deal with debris-creating operation disasters, the environmental security risks in cislunar space are enormous and poorly modelled, if fully understood at all.

While a full technical analysis of these risks is well-beyond the scope of this study (both for reasons of space and target audience) some brief discussion of the threats in cislunar space is essential, if anything to start thinking about a way of addressing them, at a governance level even before moving to an operation phase.

Figure 2 present a radar chart of the most relevant cislunar environmental security risks mapped across five critical domains, each represented as a radiating axis from the central origin. Severity intensifies radially outward on a graduated scale from 1 (low risk) at the center to 3 (high risk) at the periphery, with intermediate gradations at 2 (medium) and 2.5 (medium–high).

Fig. 2
Fig. 2
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source: author’s elaboration on data ITU, ESA, NASA, NSTC

Cislunar space domain typology severity radar chart

The polygon traces the risk profile, calculated on projections and data simulations that will be explained in the following subsections.Footnote 7

The total enclosed area of polygon provides an aggregate systemic risk metric, with larger polygonal areas signalling greater cumulative exposure across the cislunar domain.

This visualisation shows (a) RF Spectrum and (b) Functional Space Congestion as the most acute vulnerabilities in terms of projection, and therefore the ones with the largest gap areas requiring urgent regulatory intervention [a gap analysis and remediation actions is carried out in Sect. 5].

c) Debris Management presents moderate divergence, indicating emerging but not yet critical risks.

Finally, d) Orbital Position and e) Operations exhibit relatively lower profiles, suggesting adequate current governance or limited hazard levels.

At the present state, it probably requires ongoing monitoring but less urgent regulation.

4.1 Radio Frequency Spectrum: A Finite Environmental Resource

The radio frequency (RF) spectrum is one of the most urgent areas where active measures will be soon needed to avoid adverse consequences.

It constitutes a unique type of shared resource: non-depletable yet congestible, where degradation occurs not through consumption but through interference, overcrowding, and incompatible simultaneous use [104].

As in the case of air or water quality, spectrum can be polluted and rendered unusual or at least heavy degraded without coordinated governance, i.e. the "tragedy of the commons" dynamics we discussed in Sect. 1.

The International Telecommunication Union (ITU), established in 1865 as a UN specialized agency, manages global spectrum allocation through binding Radio Regulations (RR) updated periodically at the World Radiocommunication Conferences [52].

The latest RR, i.e., the RR 2024 Edition [52], allocates radio frequencies in the spectrum from 9 kHz to 275 + GHz across frequency bands, three geographic regions (Europe/Africa, Americas, Asia/Pacific), and service types (fixed, mobile, broadcasting, satellite, radio astronomy), establishing mandatory coordination procedures, interference resolution mechanisms, and enforcement frameworks based on state sovereignty and bilateral agreements, frequently updated to reflect the change in technology.Footnote 8

ITU is one of the most experienced and solid government bodies, but the last five had put a lot of strain in the governance framework, and LEO mega-constellations, already active or upcoming (Starlink, OneWeb, Kuiper, Guowang, Qianfan, etc.) are the ones mainly responsible for this situation. In addition to frequence grab cases including in the same administrative ITU regions, they generate interferences in a few service bands and create serious issues for radio astronomy [71] and even astronomical observation as a whole [63, 73, 99].Footnote 9

However, if the situation on Earth is dire, this is nothing compared to how bad it can be compared to cislunar space, an environment that fundamentally differs from the Earth’s orbits in sheer physical terms.

Simply put, the absence of atmosphere and ionospheric absorption enable cleaner long-distance signal propagation, which means interference are far more likely even along great distances. This could become extremely critical around Lagrangian points, which we have already seen maximise conditions for connectivity. In the case of satellites operating near EML1 or EML2 (therefore maintaining simultaneous line-of-sight to Earth, the lunar surface, and other cislunar spacecrafts) the vacuum of space would allow electromagnetic signals to propagate cleanly without attenuation, resulting in picking up disturbance from other antenna’s emissions or out-of-band transmissions interfering with receivers from very far away stations. A nightmare scenario.

To the vacuum of physics, we need to consider the regulatory vacuum as well.

Importantly, ITU Radio Regulations do not explicitly exclude cislunar space, but their applicability is ambiguous: “1.64 space station: A station located on an object which is beyond, is intended to go beyond, or has been beyond, the major portion of the Earth’s atmosphere,” [52, art 1.64]. This makes it potentially extendable in XGEO. This somehow clashes with other articles, such as coordination and notification [art 22], in which the coordination zones and power flux-density limits are explicitly instead designed for GEO and LEO, not Lagrange points or lunar orbit.

In any case, and this is an even bigger challenge, ITU geographic regions remain undefined beyond geostationary orbit, simply because the coordination procedures, optimised for the Earth’s orbits geometries, are incompatible with Lagrange point dynamics and the cislunar space physics as such.

Assigning frequences on EMLs will require a rewrite of several articles, and probably the creation of a bespoke geographic zone with specific guidelines and procedures.Footnote 10

The World Radiocommunication Conference 2023 [WRC-23] in Dubai, the latest to date, saw some important discussions around non-geostationary satellite systems (NGSO), particularly in new orbits and a specific focus on satellite issues. And while some initial consultations were made on specific themes (e.g., lunar SMZs and space-to-space communications; [2]) no specific agenda items regarding cislunar exploration were included.Footnote 11

The road ahead seems a long way indeed.

4.2 From Operations to SSA Establishment: Safeguarding the Cislunar Space ViabilityFootnote 12

While less immediately severe compared to RF spectrum allocations, there are other environmental threats that challenge the security and viability of expansion in cislunar space. The radar chart shows their risk threshold but does not make immediately clear how interlinked they actually are.

We have already discussed how narrow could prove to be subset of optimal orbits even in such a vast area such as the EMLs.

This creates not overcrowding as it could be in Earth’s orbits but a functional and operational congestion, in the same way it takes place in terrestrial airspace: the sky might be wide and clear but routes and approach corridors to landing points can still become crowed [37, 38, 49]. The result could be a fierce competition for strategically optimal trajectories and an unfair first move advantage for the ones that have secured earlier the best spot.

There are other important challenges that will have to be addressed before operations can be started for good on a sustained pace. If RF spectrum pollution is the cislunar equivalent of water pollution (e.g. invisible, cumulative, and reversible only through cooperative action) debris would be more alike to soil contamination. Once created, mitigation measure would be enormously difficult [15, 16, 37, 45] while tracking mechanisms are still virtually not existent. Again, the present situation in Earth’s orbits, while dire, would be not remotely compared to a breakup in cislunar space, which is a non-decaying environment where debris would stay there indefinitely unless cleaned up.

5 Closing the Gaps. A Roadmap for Cislunar Governance

“Employing a future cislunar STM architecture will be more challenging. The 10 XGEO STM volume evaluated in this work is 15.5 times larger than the SDA volume and 999 times larger than the LEO-GEO volume. With a 12-h warning time it may require 72 satellite observers to provide adequate coverage,” [108:5].

One of the aims of Fig. 2 is to transform multidimensional cislunar sustainability challenges into an actionable (visual) roadmap for mapping possible governance interventions. Without a measurable target sustainability threshold, showing where the current-state polygon extends beyond a (hypothetical) target boundary, signalling where the governance gaps are more urgent, its applicability, however, remains theoretical. This is one of the limitations of the present study, which will need more data and analysis for the model to become more functional (Tables 1 and 2).

Table 1 Elms definitions
Full size table
Table 2 A comparison between earth’s orbits & cislunar space conditions
Full size table

Still, it can offer important indication in terms of gap analysis and a roadmap for remediation [36], as presented in Table 3.

Table 3 Top environmental gaps in cislunar space
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The literature is almost univocal in advocating measure for additional research and experimentation to the relatively unknown cislunar SSA setting that will need to exist to avoid the nightmare scenario discussed in the previous section.

These are of course early days, but some solutions will have to be found relatively quickly in the next 5–10 years, as we assessed on the threat matrix shown before.

Which takes us back to the most serious challenge that must be made to make sure to successfully tackle all the issues we previously examined: a shared cislunar governance that can prevent them to happen in the first place.

If we reframe what we identified as cislunar space threats in the previous section, we end up with a list of main gaps to close before we face the likely adverse consequences.

These are the starting points from where the remediation actions begin to fill the gap before the cislunar space reach the difficult (if not impossible) to reverse conditions discussed in Sect. 4.

Given the lack of clear data and relatively limited studies, they are still largely conceptual. But they are sufficient to indicate a roadmap for future actions.

5.1 Cislunar Spectrum Protocol (RF Governance)

Cislunar communications must be classed as critical infrastructure rather than an open-access commons, the way they are strictly regulated on Earth [52]. As discussed in Sect. 3 and 4, without a clear allocation and coordination, cumulative interference will degrade navigation, teleoperation, and safety-of-flight services [36, 74, 89]. A dedicated protocol will have to establish predictable electromagnetic order across the Earth–Moon system.

There are some important technical aspects that will have to be taken into consideration (corridor-based spectrum filings tied to NRHO and EMLs, preapproved material registers for components prior to deployment, mandatory emission masks to prevent out-of-band leakage and spillovers, power transmission thresholds) to limit as much as possible systemic RF pollution [21, 55].

Finally, cross-country coordination tools and shared databases would help prevents conflicts, solve adjudication clashes and adjust scheduling to avoid congestion, shifting governance from dispute resolution to prevention.

5.2 Cislunar Debris Prevention Measures

One of the main challenges discussed in Sect. 4 is that debris in cislunar space does not naturally decay. Even minor fragmentation events can and will create permanent hazards and operation disruption on a scale unseen (so far) on Earth.

Preventive measures will be absolutely mandatory to ensure the sustainability of cislunar operations [15, 3, 13]. This will require protocols that do not exist yet on Earth but whose effectiveness will have to be flawless in cislunar space. Probes and satellites will have to adhere to strict design standard preventing all causes of debris formation [33, 44], from explosions to break-up scenarios, and include a clear-cut end-of-life de-orbit solution. These safeguard regulations should be clearly linked to licensing, without which no operations should be allowed.

Immediate reporting of breakup events and close monitoring of them from a supernational agency will ensure the possibility of deployment of ADR measures to address the issues.

5.3 In-Orbit Operations, Safety Regulations, and SSA

The clear and most urgent gap to close here is to set up operational traffic management at strategic nodes, such as the Near-Rectilinear Halo Orbits (NRHO) and EMLs [37, 42]. As they will function as cislunar logistics hubs this will require structured traffic management to prevent coordination failures as activity scales, and, therefore, radio interferences or, worse, debris creation. Standardised approach and departure corridors, analogous to aviation airways, can enable efficient tracking and deconfliction through common routing.

A functional coordination of the kind we see on Earth with IATA will be required to ensure resilience and interoperability, with standardised incident reporting protocols and response playbooks for emergency scenarios and fragmentation events. This will be absolutely crucial to safely scale up operation with multiple countries/ operators, especially if, as it is likely, they will adopt different protocols [89].

Last but not the least, the creation of a bespoke cislunar SSA (Space Situational Awareness [5, 6, 8, 9, 43]) as a foundational infrastructure that ultimately control and supervise governance mechanisms enforcement will be essential, although this is probably the most challenging to achieve. But a multilateral agreement on standards and mission planning procedures will be mandatory to prevent conflicts, misunderstandings and avoid catastrophic incidents.

5.4 Filling the Governance Gap

The clear precondition to create the conditions for the remediations discussed in the previous section remains, of course, filling the multilateral governance vacuum in cislunar space.

This requires urgent institutional consultations at the highest levels across multiple diplomatic venues and forum.

The first and most obvious is the UN Committee on the Peaceful Uses of Outer Space (COPUOS), which has the merit of already having successfully developed Long-Term Sustainability (LTS) Guidelines for Earth orbit [100].

Extending COPUOS's mandate would mean using the existing regulatory and technical expertise in a way that secures multilateral participation. This large participatory setting is essential in the medium-long term viability of the decisions adopted, especially if they are going to be stringent, as they will likely be.

However, and this is a bane multilateral bodies are fraught with, consensus-based decision-making within COPUOS's 100 + member states presents significant constraints in terms of reaching timely decisions, especially given the accelerating pace of cislunar activities [54].

For the delicate RF spectrum allocation of frequences, an effective governance in cislunar space will requires coordinated action across several domains, diplomatic, technical, operational among others. This is probably the one simplest to address: the ITU has 150 + years of experience in handling them on Earth. It could incorporate in its jurisdiction the cislunar spectrum management, possibly in a dedicated agenda item at upcoming World Radiocommunication Conferences [WRC-27 or WRC-31, if 2027 is too early for an operational roadmap] to prevent spectrum-grab scenarios from first-mover players. Eventually, it could set up a Cislunar Spectrum Coordination Authority as a specialized ITU body, in coordination with UN COPUOS, to overseas possible (and likely) interference disputes, and enforce compliance.Footnote 13

Regional and bilateral agreements, in primis the Artemis Accords, offer a short-term but still potentially precious interim solution with immediate measures. Now signed by 50 + nations, they are establishing preliminary norms especially in functional and operational terms, though their legally non-binding nature limits enforceability [27, 87].

Moreover, the fact that central players in outer space (e.g., Russia, China) have not subscribed them creates further gaps. Technical coordination frameworks, such as the NASA-ESA LunaNet interoperability standards, show a way forward in which technical cooperation creates de facto governance structures ahead of formal treaties [66, 69]. There is an obvious risk that fragmented approaches from different space agencies result in an incompatible regulatory setting [51]; let alone when the field of application is blurry or poorly defined, as clarified in Sect. 3 [22, 23]. Yet, they have the value of providing immediately applicable operational guidance where none are present.

Another complex point relates to the integration in the overall space governance of commercial and/or private space actors, which remains to date critically underdeveloped on Earth, let alone in cislunar orbit [48, 55, 56]. The emerging national legislations are full of jurisdictional ambiguities, in particular to the ‘resources’, however defined, beyond geostationary orbit, leaving cislunar (and in general XGEO) commercial operations in regulatory limbo [50]. A working governance framework will require aligning commercial interests with sustainability objectives through multilaterally negotiated licensing conditions (for RF and strategic orbital points), an expanded liability frameworks extending Outer Space Treaty Article VII to environmental damage, and market-based, or commercially negotiated mechanisms such as orbital-use fees or debris-mitigation bonds [104].

All these intermediate, partial measures should ideally converge in a comprehensive Cislunar Environmental Protocol, analogous to the Antarctic Environmental Protocol (1991), which would tackle all the five gaps of the tables and establishing binding obligations for debris mitigation, spectrum coordination, cislunar SSA, and more in general, outer space operation sustainability.

The Protocol should incorporate quantitative sustainability metrics [16, 26, 65, 64, 67], mandatory environmental impact assessments for major cislunar missions, and enforceable penalties for non-compliance. As in the case of the Earth’s orbits, the regulatory challenge lies not, or not only, in technical feasibility but in a shared, global agreement on best practice and solid governance guidelines before unsustainable practices become unreversible.

6 Conclusions: Environmental Security and Governance as a Precondition for Cislunar Sustainability

In 2026, dangers and opportunities of the space sector are under everybody’s eyes.

“The opportunity is real, but so are the risks. Orbital congestion, debris, cyberthreats, and a first-come, first-served approach to spectrum and prime orbital slots could turn access into exclusion. Just a few entities still own most of the active satellites in a few countries, and coordination rules can be hard to navigate for agencies with thin budgets and small technical teams,” [106:16].

If this is true for the space sector on Earth, this is even more the case for the cislunar orbit, which not only presents some unique characteristics but also opportunities [1, 18, 21, 34, 35]; yet, it is also of such a complex access that a first-mover advantage has the possibility to make it inaccessible to the rest of the humanity in space.

Protecting the environment of this peculiar region between Earth and the Moon is a critical security concern, far beyond a simple engineering problem. We have seen here how the radio frequency (RF) spectrum is a fragile, finite environmental resource, and its health is vital even absent a traditional concept of ‘depletion’.

More broadly, the entire cislunar environment, encompassing orbital mechanics, debris accumulation, and resource availability, represents a delicate system demanding careful stewardship. Earth benefit from roughly 150 years of governance experience, a history marked by imperfect but ultimately functional frameworks for managing shared resources.

Nonetheless, we've seen how postponing rules in Low Earth Orbit (LEO) and Geostationary Orbit (GEO) has resulted in lasting damage, like the impeding danger of a Kessler Syndrome (satellite debris cascade) and progressive crowding of radio frequencies.

The stakes are even higher in cislunar space, which currently lacks any established governance structure, despite physical conditions that render coordinated action even more critical for long-term sustainability. The International Telecommunication Union's (ITU) existing regulatory framework, designed for terrestrial and near-Earth operations, is geographically and technically inapplicable to the unique challenges of cislunar space. Its parameters and assumptions don't account for the vastly different distances, orbital dynamics, and long-term environmental impacts prevalent in this region.

Equally critical is debris, which once formed will remain hovering for vast stretches of time [23]. Vital scientific opportunities like the Moon's shielded zone could be lost forever [51], as the space will not naturally clean itself up [4] in shorter or longer timespans like in Earth’s orbits.

The regulatory vacuum only adds to this situation.

As argued in the previous section, cislunar space governance is underdeveloped [102, 105], crippled by competing definitions about its domain, and relies only on voluntary agreements like the Artemis Accords, which lack enforcement [27] and are not being negotiated on a multilateral basis. Following Ostrom [81] on managing shared resources under the lenses of environmental security, this article argues that preventive and proactive governance is both possible and urgently needed.

Without proactive intervention, the cislunar RF environment, and the broader cislunar space environment, faces a “tragedy of the commons” scenario significantly more severe than the congestion already observed in Low Earth Orbit. The time at our disposal is limited, with a window of opportunity that rapidly closing (over 50 missions are planned by 2035). Without robust, enforceable frameworks, we risk repeating the LEO mistakes in a region of space where the costs of error are exceedingly elevated and restoration is impossible.