1.2 Phases and uncertainties Because operational practices evolve over time, the model does not assume a single, static future. Instead, it projects the risks from 2025 to 2040 in three developmental eras: Confidence intervals applied to each five-year modelling phase TABLE 1 Phase Period Description Uncertainty Constellation revolution 2025–2030 Rapid deployment of large constellations per ITU filings ±10% Constellation maturity 2030–2035 Improved reliability, lower failure rates ±20% Constellation evolution 2035–2040 Mergers, migration to lower orbits ±50%These uncertainty levels determine the confidence intervals applied to each five-year modelling phase. In practice, they define how widely the model’s outputs – such as object counts, collision probabilities and debris growth rates – may vary from baseline scenarios. A ±10% uncertainty reflects relatively reliable inputs, since near-term launch manifests and constellation plans are well documented. By contrast, the ±50% uncertainty reflects the compounding unpredictability of future operator behaviour, market consolidation, regulatory enforcement and unplanned fragmentation events. The wider the uncertainty band, the greater the dispersion of projected debris densities and collision risks that feed into the economic model. 1.3 Translating population into risk Even small annual probabilities accumulate to form a notable threat across tens of thousands of spacecraft. For instance, a satellite operating near 805 km in 2035–2040 faces a 1.5% chance of an anomaly and a 0.55% chance of mission-ending impact per year, small individually but substantial collectively. To translate broad projections into specific risk probabilities for a typical satellite, it is crucial to understand the annual likelihood of an impact for a representative satellite (3 m2 cross-section) from three different categories of debris, each with a different real-world consequence. Specific risk probabilities for a typical satellite TABLE 2 Symbol Description Likely effect PC(HNT) Probability of collision by hazardous non-trackable debris (5 mm–1 cm)Causes a non-mission-ending anomaly, such as temporary service disruption or partial damage PC(LNT) Probability of collision by lethal non-trackable debris (>1–10 cm)Causes mission-ending damage or total loss of the satellite PC(Cat) Probability of close approach with tracked objectRequires an operator to perform a collision-avoidance manoeuvre Clear Orbit, Secure Future: A Call to Action on Space Debris 9

Clear Orbit Secure Future 2026