The LEO is increasingly crowded with inactive satellites, rocket stages, and other debris, posing a risk to spacecraft operations. According to current estimates (European Space Agency, 2025b), there are an estimated 1.2 million objects capable of causing damage. Of these, 50,000 large objects are particularly capable of triggering catastrophic fragment-generating collisions through the Kessler Syndrome (Space.com, 2025). This effect describes a regime in which increasing object density causes self-sustaining collision cascades, severely disrupting existing satellites. Kessler’s collision frequency C scales approximately as: C ∝ n 2 σ v

Where n is object number density, σ is effective cross-sectional area, and v is relative velocity. Since collisions scale with n ², even small reductions in n will disproportionately reduce collision frequency, creating a nonlinear positive feedback loop (Kessler and Cour-Palais, 1978). Additionally, larger objects have greater σ, yielding higher collision probability. Thus, debris mitigation policies should aim to remove large objects due to cascading effects on LEO ecosystems. While mitigation efforts in the status quo, they are insufficient to prevent long-term instability (Liou and Johnson, 2006). Long-term risks of orbiting debris in the LEO are projected to increase, which is demonstrated by simulations graphing the Total Number of Objects in Orbit Over Time. Using existing data from NASA Orbital Debris Charts (NASA Technical Reports Server, 2024), Figure 1 shows that recent years have seen an exponential increase in debris; this may be attributed to the privatization of space, necessitating active removal.

Recent attempts to remedy this issue, such as the FCC 5-year deorbit rule (Federal Communications Commission, 2024), have failed to successfully address this issue. As the rule only requires satellites in the LEO to deorbit within 5 years after mission completion, it does not prevent collisions that are resultant of existing large objects. Additionally, it measures time, not risk; treating all post-mission satellites as equally hazardous is misguided, as collision risks differ by object size. Different measures, such as ADR, have emerged as potential solutions, with previous missions such as RemoveDEBRIS (University of Surrey, Surrey Space Centre, 2025), ClearSpace-1 (European Space Agency, 2025a), and Astroscale ELSA-d (Astroscale, 2025) demonstrating improvements in the feasibility of capturing and removing debris. However, such attempts often focus on single missions, without long-term enforcement or accountability upon organizations. At most, these have consisted of technology demonstrations without large-scale action. Evidently, ADR must become more widely applied to meaningfully reduce debris risks. So, this raises a critical question: At what rate will ADR become measurably more effective than mitigation alone?

Unlike previous studies that evaluate ADR feasibility or simulate long-term debris evolution, this study aims to identify whether a nonlinear transition point exists at which ADR qualitatively alters long-term debris dynamics (Liou, 2011) under an existing regulatory regime. This analysis is intentionally exploratory in nature, and the emphasis is on detecting regime change under policy assumptions, not predicting exact quantitative results. Thus, analysis can reframe ADR as a policy design variable rather than a purely technical variable.

This study focuses on debris in the 500–600 km range of LEO, which is densely populated and long-lived with respect to orbital decay. Many commercial and scientific missions including Starlink operate in this range, making collisions highly detrimental. Mitigation rules such as the FCC 5-year deorbit rule are designed for this range due to its long-term risk. Objects within this region experience slow natural deorbiting, making it particularly sensitive to long-term debris growth and high collision risk. Thus, it is exceedingly relevant to study 500–600 km LEO. This analysis is restricted to large objects (>10 cm), as they have the most consequential collisions and generate the majority of debris fragments.

Orbital debris was obtained from publicly available Two-Line Element (TLE) sets from CelesTrak and Space Track archives. Analysis modelled long-term population trends as well as current counts of satellite debris to determine a baseline. To ensure minimal error, analysis removed duplicate objects with incomplete orbital parameters to preserve consistency of datasets. Gemini AI assisted in code generation with manual verification.

The simulations revealed that while standard FCC 5-year deorbit rules slow the rate of collision risk increase, it will not prevent the debris environment from worsening. Thus, more proactive measures such as ADR are necessary in order to stabilize debris counts in the next 30 years.

Figure 2 compares Estimated Debris Count (LEO 500–600 km) vs. Time. The baseline scenario, assuming 90 percent compliance +0 ADR, saw a 517.3 percent increase in debris count. A total of 2,142 debris (±30) were estimated by 2055. Each incremental increase in ADR saw a decrease in projected debris counts. The analysis indicates that the threshold for when ADR succeeds in reducing the debris population is removal of ∼60 objects per year. However, this number is scenario-specific, and a proxy rather than a universal value. This value should be interpreted as an illustrative marker of regime change rather than a precise quantitative requirement. In this scenario, there was a 1.44 percent decrease, meaning that the debris population shrunk, as large objects that were primed for collision were removed. While ADR of 10–50 large objects succeeded in flattening the curve, the total number of debris continued to rise. Thus, these did not stabilize the environment to the degree necessary by this study’s metrics. As seen in the scenario assuming ADR of 5 objects, removing greater amounts of debris will incrementally decrease the estimated environmental debris. This places the system further into the region of negative net debris growth, where not only is debris stabilized, but it is also reduced. While this is the ideal scenario for future policy recommendations, it is not always realistic as ADR is cost-intensive and institutionally complex. This reveals the utility of a “threshold”: if removal of 80–100 large objects is not feasible, it is important to remove at least ∼60.

This was supported by Figure 3, which used object density x cross-section x relative velocity as a proxy. Under this simulation, the flux metric represents relative collision intensity, where a higher flux correlates to more frequent collisions. In the baseline scenario, flux rate increased linearly. Even assuming compliance as high as 90 percent, the status quo will see increasingly difficult operations. Thus, Figure 3 demonstrates that current compliance is not enough, as the risk fails to drop. This is contrasted to ADR, which shows a downwards trend in flux.

Specifically, in scenarios assuming ADR of at least ∼60 large objects, the collision flux declined significantly, indicating a sustained reduction in collision flux. While the collision risk declined below its baseline value at ADR 70 and 80, the resultant debris growth from projected collisions in ADR 60 is still net negative; thus, positive collision growth can still produce net negative debris due to less colliding objects.

Therefore, the threshold is impactful in multiple metrics; removal of large objects reduces the chances of high-energy collisions, which in turn generate smaller fragments upon impact.

In order to more quantitatively determine the marginal benefit per object removed, simulations analyzed Net Growth Rate vs. ADR Level. Figure 4 depicts the net growth rate of debris in a bar chart, which helps to locate the “tipping point”, or where the bars turn negative.

This point occurred at ∼60 ADR, where negative numbers represented the net remediation benefit; this was where debris was removed faster than it was added. Following, this backs up that removing at least ∼60 large objects per year has significant benefits; not only does it stabilize debris growth and reduce collision risks, but it causes a net decrease in added objects per year, actively remediating environments. The identified threshold is supported by trends across multiple metrics, including debris population growth and net growth rate, and is not inferred from the collision proxy alone.

Therefore, even near perfect compliance with current mitigation will result in stagnation, not recovery. Failure to shift mitigation efforts will prove detrimental, with debris accumulation becoming increasingly positive; this will magnify the risk of collisions that severely harm existing and future space operations. Thus, it is beneficial for regulators to shift to more proactive measures. This may look like adopting qualitative ADR targets, which sets reasonable goals for future policies. However, it is necessary to clarify that the identified threshold is not proposed as a fixed regulatory mandate, but rather as a reference point that may inform long-term policy design. Policy implications should be framed around shifts in system behavior rather than exact targets. Because the results depend on simplified dynamics and controlled assumptions, the value of this study primarily lies in informing directional policy. Specifically, policymakers may consider centering removal around ∼60 large objects per year, which offers high potential for a trajectory towards sustainable recovery. This precise numerical threshold is contingent on idealized assumptions, but the existence of a minimum viable ADR regime is still a robust implication of nonlinear collision dynamics, making it useful for informing policy. While current technological limitations limit the probability of achieving this exact value, it is important for policymakers to consider the demonstrated potential of ADR. Groundworks laid in RemoveDEBRIS, ClearSpace-1, and Elsa-d support the potential for achieving this threshold, providing a concrete focal point for future mitigation efforts; however, this study proves that limited ADR utilized in these projects is insufficient at its current scope. The potential of substantially increased ADR rates reaching orbital sustainability is evidenced by simulations modelling debris population growth and the collision proxy, which is a useful indicator of relative risk reduction, but is not intended to justify precise safety claims. In order to guide their recommendations, regimes may consider requiring ADR capacity as a condition for approval of major new launches, which aligns incentives and encourages large-scale adoption. Importantly, this does not necessitate a single actor being held liable for the removal of ∼60 objects annually. Rather, it is more realistic for this requirement to be distributed across corporations, countries, and licensing regimes. While ADR remains expensive, the relatively low number of necessitated removals demonstrates feasibility through collective, sustained action. Framing ADR as a collective goal rather than individual mandate reduces widespread resistance and offers potential for long-term sustainability. This study demonstrates that ADR is not only a preventative measure but also may actively reverse long-term instability if properly legislated.