Space sustainability is the capacity to use orbital and cislunar environments safely, equitably, and without degrading the conditions that future missions and future generations will need. It sits at the intersection of orbital debris mitigation, spectrum coordination, collision avoidance, and the broader governance of shared space infrastructure. For states in Africa, Latin America, Southeast Asia, and small island nations, the question is not whether space sustainability matters, but whether the institutions that measure and enforce it will reflect their interests. A Space Sustainability Index would make visible the gap between treaty language and operational reality, and it would give smaller space actors a tool to hold larger ones accountable.
This article argues that a public, independently maintained index is a necessary institutional response to the accelerating congestion of low Earth orbit. It is not a substitute for binding rules, but a mechanism for making non-binding norms legible, comparable, and politically actionable. The index should be designed with the same care as the orbital systems it evaluates.
Why an Index, and Why Now
The current governance architecture for space sustainability is fragmented. The Outer Space Treaty of 1967 establishes broad principles, including the obligation to avoid harmful contamination of space and celestial bodies. The Liability Convention and Registration Convention create partial accountability mechanisms. The Inter-Agency Space Debris Coordination Committee has produced widely cited debris mitigation guidelines, and the UN Committee on the Peaceful Uses of Outer Space has endorsed a set of long-term sustainability guidelines. Yet none of these instruments provides a clear, comparable measure of how individual states or operators are performing over time.
An index would fill that gap. It would aggregate data on debris production, post-mission disposal rates, collision avoidance practices, registration completeness, and compliance with international guidelines. It would not replace the existing treaty system, but it would make the system’s implementation gaps harder to ignore.
The urgency is not hypothetical. The number of tracked objects in orbit has risen sharply with the deployment of large constellations. The European Space Agency estimates that more than 36,000 objects larger than 10 centimeters are currently tracked, with many more smaller objects untracked. Even a small fraction of these objects colliding can generate cascading debris, a scenario known as the Kessler syndrome. For equatorial and low-latitude states, the risk is not evenly distributed. Debris in low Earth orbit passes over all latitudes, but the capacity to track, predict, and avoid it is concentrated in a handful of spacefaring nations.
What the Index Should Measure
A credible Space Sustainability Index must be built on observable behavior, not aspirational statements. The following categories are essential.
1. Debris Mitigation Compliance
This includes the share of a state’s or operator’s spacecraft that successfully complete post-mission disposal within the recommended 25-year window, the use of passivation measures to prevent explosions, and the release of mission-related debris. The index should distinguish between design compliance and operational compliance. A satellite may be designed to deorbit, but if it fails before the maneuver is completed, the design promise means little.
2. Collision Avoidance Transparency
States and operators receive conjunction warnings from the U.S. Space Surveillance Network and, increasingly, from commercial providers. The index should track whether operators publish their collision avoidance policies, share ephemeris data, and participate in data-sharing platforms such as the Space Data Association. Transparency here is not a bureaucratic nicety; it is a form of risk reduction for everyone.
3. Registration and Identification
The Registration Convention requires states to register space objects with the UN. Yet many objects remain unregistered or are registered late. An index should measure registration timeliness, completeness, and the accuracy of orbital information. For smaller states, this is a matter of legal clarity: if an object causes damage, the victim must be able to identify its owner.
4. Spectrum and Orbital Slot Discipline
Radio frequency interference and orbital slot squatting are sustainability problems too. The International Telecommunication Union allocates spectrum and orbital positions, but enforcement is weak. An index could track how often operators exceed their assigned power levels, cause harmful interference, or fail to bring satellites into use within the required timeframe.
5. Capacity Building and Equitable Access
Sustainability is not only about avoiding harm; it is also about ensuring that the benefits of space are shared. The index should include a measure of how states contribute to capacity building, data sharing, and training for emerging space actors. This is particularly relevant for the blog’s focus regions, where space agencies are young and budgets are limited.
Design Principles for the Index
An index is only as good as its methodology. The following principles should guide its design.
Independence from Single-State Control
The index should not be owned by any single spacefaring nation. A consortium of universities, research institutes, and civil society organizations from multiple regions would be more credible. The Space Sustainability Rating, developed by the World Economic Forum, the European Space Agency, and the Massachusetts Institute of Technology, is a useful starting point, but it is voluntary and operator-focused. A state-level index would complement it.
Open Data and Reproducibility
Every score should be traceable to public data sources. If a state disputes its score, it should be able to see exactly which data points were used and how they were weighted. This is not just a technical requirement; it is a legitimacy requirement. An index that cannot be audited will not be trusted.
Differentiated Baselines
Not all states have the same capacity to comply with sustainability guidelines. A state that has launched three satellites should not be judged on the same scale as one that has launched three thousand. The index should use per-capita or per-launch metrics where appropriate, and it should include a separate measure of capacity-building contributions so that smaller states are not penalized for their size.
Forward-Looking Indicators
The index should not only measure past behavior. It should also track commitments, such as pledges to join the Zero Debris Charter or to adopt the UN long-term sustainability guidelines. These forward-looking indicators create incentives for improvement, not just punishment for past failures.
What the Index Would Reveal
A well-designed index would expose several uncomfortable truths. First, the gap between treaty ratification and treaty implementation is wide. Many states have ratified the Outer Space Treaty and the Registration Convention but have not enacted domestic legislation to enforce their obligations. Second, the largest space actors are not necessarily the most sustainable. High launch rates can mask low compliance rates if the denominator is large enough. Third, the burden of space debris is not shared equally. States that have contributed little to the problem may face disproportionate risks because they lack the tracking and avoidance infrastructure to protect their assets.
For the blog’s core audience, these findings matter. A state in Southeast Asia that is planning its first Earth observation satellite needs to know which launch providers and which orbital regimes are safest. A small island state that relies on satellite communications for disaster response needs to know whether the constellations it depends on are managed sustainably. An index would give these states a common reference point.
Objections and Tradeoffs
Critics will argue that an index is too soft, that it cannot force compliance, and that it may be gamed. These objections have merit. An index is not a treaty. It cannot impose sanctions or revoke licenses. But soft instruments can shape behavior when they are tied to reputation, market access, and diplomatic standing. The Corruption Perceptions Index and the Environmental Performance Index have influenced national policy without any binding force. The same can happen in space.
There is also a risk that an index could be captured by the very actors it is meant to evaluate. To mitigate this, the index should be governed by a multi-stakeholder board with representation from all regions, and its methodology should be subject to periodic independent review. No single state or company should have veto power over the indicators.
Finally, some will argue that an index is premature because the data are incomplete. It is true that many states do not publish detailed information about their space activities. But the index can be designed to work with the data that are available, while also creating pressure for more transparency. A state that refuses to publish its debris mitigation data would receive a low transparency score, which is itself a meaningful signal.
A Regional Perspective
The index should not be a tool of the Global North. It should be co-designed with input from Africa, Latin America, Southeast Asia, and small island states. These regions have a direct stake in space sustainability, but they are often absent from the technical working groups where the rules are written. An index that is developed in Geneva or Washington and then exported to the rest of the world will not be legitimate.
One practical step is to establish regional data hubs that collect and verify sustainability data from local operators. These hubs could be hosted by regional space agencies or universities, and they could feed into the global index. This would build local capacity while also improving data quality. It would also create a natural next step for this blog: a recurring column that tracks the index’s development and highlights regional contributions.
From Measurement to Action
An index is not an end in itself. It is a tool for changing the conversation. Once states and operators can be compared on a common scale, the next step is to use that comparison to drive policy. The index could inform launch licensing decisions, insurance premiums, and bilateral cooperation agreements. It could also be cited in UN debates and in national space legislation.
For the blog’s editorial thesis, the index is a natural fit. It connects the abstract language of international space law to the concrete realities of orbital infrastructure. It gives smaller states a way to assert their interests without waiting for a new treaty. And it creates a durable content pillar: a series of articles that explain the index’s methodology, profile its regional partners, and analyze its findings.
The case for a Space Sustainability Index is not a case for more bureaucracy. It is a case for making the existing system work better. The treaties and guidelines already exist. What is missing is a way to see whether they are being followed. An index would provide that visibility, and visibility is the first step toward accountability.
Frequently Asked Questions
What is a Space Sustainability Index?
A Space Sustainability Index is a composite measure that scores states or operators on their adherence to space sustainability practices, including debris mitigation, collision avoidance transparency, registration compliance, and capacity building. It is designed to make non-binding guidelines comparable and politically actionable.
How would a Space Sustainability Index help smaller space actors?
Smaller states often lack the tracking and avoidance infrastructure to protect their satellites. An index would give them a common reference point to assess the sustainability of launch providers, orbital regimes, and constellation operators. It would also create pressure for more transparent data sharing, which benefits all actors but especially those with limited resources.
Is a Space Sustainability Index legally binding?
No. An index is a soft governance instrument. It cannot impose sanctions or revoke licenses. However, soft instruments can shape behavior through reputation, market access, and diplomatic standing. The Corruption Perceptions Index and the Environmental Performance Index have influenced national policy without binding force, and a space sustainability index could do the same.
Who should maintain the index?
The index should be maintained by a multi-stakeholder consortium of universities, research institutes, and civil society organizations from multiple regions. It should not be controlled by any single spacefaring nation. Regional data hubs in Africa, Latin America, Southeast Asia, and small island states could feed into the global index, building local capacity while improving data quality.
This article is part of a series on institutional design for space governance. A follow-up piece will examine how regional data hubs could be structured and funded.