Rules that pay rent: debris mitigation on the graph

Agent rules that pay rent are operational guidelines that must be checked against real-world data to assess compliance. In the context of space debris, these rules are used to evaluate the state of satellites and other objects in orbit. The process involves querying a structured graph of space objects and deriving signals from the data. These signals must be both precise and traceable to their assumptions to be useful in safety-critical domains. This lesson explores how compliance signals can be computed symbolically from a graph of space objects.

Signal Computation from Graphs

The same computational machinery that evaluates mappings between objects can also compute operational signals. This machinery applies three distinct rules, each with its own set of assumptions, to a structured graph of space objects. These rules are executed in seconds, providing a rapid assessment of compliance with debris mitigation guidelines. The process involves traversing a graph where nodes represent space objects and edges represent relationships such as launch date, operational status, or orbital decay. The output of each rule is a signal that reflects the state of the system under a specific assumption.

Each rule operates under a specific assumption ledger, which documents the conditions under which it is valid. These assumptions are essential to interpreting the signal correctly. For example, one rule assumes that objects launched more than 25 years ago are likely to be non-operational. The signal derived from this rule is a count of objects that meet this criterion, along with metadata about their status and type.

Debris Mitigation Guidelines and Baseline Limits

The baseline limits for post-mission Low Earth Orbit (LEO) lifetime are defined by the Inter-Agency Space Debris Coordination Committee (IADC) guidelines. These guidelines set a maximum allowable orbital lifetime of 25 years after the end of a mission. The United States Federal Communications Commission (FCC) updated its policy in 2024 to align with a stricter 5-year limit. The European Space Agency (ESA) has also adopted a “Zero Debris” approach that pushes for even more stringent controls.

These policy changes reflect a growing awareness of the risks posed by space debris. The IADC guidelines, which have long served as a reference point, are being supplemented by more restrictive national regulations. This evolution in policy has necessitated more precise and timely compliance checks. The computation of signals from a structured graph allows for rapid updates to reflect these regulatory changes.

Rule One: The 25-Year Lower Bound

The first rule applies a 25-year threshold to in-orbit LEO objects that were launched more than 25 years ago and are no longer in a mission state. Because the orbital catalogue records launch dates rather than mission end dates, this is a stated lower bound. The result of applying this rule is a count of 10,016 objects. These objects are further categorised into 1,356 non-operational or unknown-status payloads, 636 rocket bodies, and 8,024 debris fragments. This breakdown is derived from the orbital catalogue and reflects the current status of these objects.

This rule highlights a key challenge in debris tracking: the ambiguity of object status over time. The 10,016 objects identified are those that have survived at least 25 years, but their exact status remains uncertain. The breakdown into payload, rocket body, and debris fragment types provides further granularity. The total number of in-orbit LEO residents is 28,238, so the 10,016 objects represent approximately 35.5% of the total.

Rule Two: Internal Consistency Check

The second rule checks for internal consistency by identifying rows in the catalogue that have both a decay date and an operational status. The result of this check is zero. This clean negative indicates that the catalogue’s own bookkeeping is internally consistent on this axis. The signal is a negative one, which is still valuable in compliance reporting.

This consistency check is critical for ensuring that the data used in compliance assessments is reliable. A negative result does not mean the catalogue is perfect, but it does indicate that there are no obvious contradictions in the data. The zero result is a direct consequence of the assumption that decay dates and operational statuses should not co-occur for the same object. This rule helps validate the integrity of the data before applying other checks.

Rule Three: Graveyard Compliance

The third rule targets non-operational geostationary orbit (GEO) band payloads that have not been moved to a graveyard orbit. The result of applying this rule is 619 candidates for disposal. These objects are identified based on their operational status and orbital location. The guidelines require that such payloads be raised to a graveyard orbit to prevent collisions.

This rule is particularly important for GEO satellites, which are more difficult and expensive to move. The 619 candidates represent a potential risk to other operational satellites. The identification of these objects is a direct result of the graph-based query system, which can quickly identify objects that do not meet the disposal criteria. The signal from this rule is a count of objects that require further action.

What to take away

Compliance dashboards should query an explicit graph with assumption notes to ensure that signals like 10,016 are meaningful and traceable. This approach allows for more accurate and reliable assessments of space debris. The practice models a method where compliance is not just a number, but a result of clear assumptions and data-driven checks. This structured approach is essential for maintaining safety in the increasingly crowded orbital environment.

Reference

Sources and further reading

• IADC mitigation guidelines (UNOOSA hosting)
• Rules with assumption ledger

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