75
th
International Astronautical Congress (IAC), Milan, Italy, 14-18 October 2024.
IAC-24- A6.10-E9.4.11 Page 1 of 13
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Integrating Orbital Carrying Capacity into International Policy Constructs: Leveraging best practices
from aviation's risk-based norms
Dr. Ruth E. Stilwell
a
*, Dr. Nathaniel Dailey
b
, Zhanna Malekos Smith
b
Dr. Darren McKnight
c
a
Aerospace Policy Solutions, LLC, 275 Commercial Blvd., Suite 210, Lauderdale-by-the-Sea, Florida, 33308 USA.
office@aerospacepolicysolutions.com
b
MITRE, 7525 Colshire Dr., McLean Virginia, 22102. USA. ndailey@mitre.org, zmalekossmith@mitre.org
c
LeoLabs, 4795 Meadow Wood Lane, Chantilly, VA 20120 USA. darren@leolabs.space
* Corresponding Author
Abstract
This paper proposes modeling an orbital altitude-based "LEO Class" based on aviation's Airspace Class approach that
considers traffic volume and complexity in establishing entry requirements for particular airspace volumes. Orbital
capacity, like airspace capacity, should consider the characteristics, behavior, and capabilities of objects operating at
particular altitudes coupled with the precision and accuracy of space situational awareness. Carrying capacity at its
core is a safety metric, improvements in collision avoidance capability, including SSA and maneuverability, can
increase the carrying capacity of a specific orbit, but may be constrained by the least capable actors.
For aviation, the requirement to accommodate various airframe types, from experimental home-built aircraft to
advanced airliners, operating in airspace ranging from low density to highly congested, led to the existing international
framework for aviation safety, using a well-organized set of airspace classes. The aviation framework of Airspace
Class establishes performance standards for entry into a specific airspace volume by considering the complexity,
congestion, and risk in the airspace volume itself. Higher airspace classes have higher entry requirements to mitigate
collision risks while airspace volumes with lower collision risk remain accessible to lessor equipped operators through
lower entry requirements. Airspace Class is clearly defined and transparently disseminated, allowing operators to self-
select operating zones according to their willingness and ability to fulfill entrance criteria. Orbital altitude-based
approaches, defining LEO Classes using Airspace Class as a model, complement ongoing efforts, like the Space
Sustainability Rating (SSR), and provide a necessary incentive structure to accelerate acceptance and codification of
norms of behavior in space. This proposal suggests implementing higher safety requirements for altitudes where
resident missions are paramount, and mishaps have more significant consequences.
In this scenario, “consequence” encompasses the immediate risk to generate debris, the potential for collision with
operational missions, and the long-lasting nature of this collision threat. Debris persistence is a distinctive aspect of
space safety compared to aviation. A combined LEO “Airspace” protocol and tools like the SSR framework may
contribute to better defining the essential safety requirements and incentivizing responsible behavior. Modeling an
existing globally harmonized approach can provide a path to achieve safe space sustainability goals.
While norms of responsible behavior must encompass equitable access for established and nascent space actors,
adopting a uniform framework that applies to all orbital paths may result in the establishment of inadequately low
performance thresholds in congested orbits which affects risk, or excessively stringent criteria in sparsely utilized
orbits which inhibit experimental endeavors and innovation. An orbital classification system mitigates these risks by
creating clearly defined requirements for specific orbital ranges rather than attempting to develop one standard that
applies to all orbits.
Keywords: Keywords: orbital classification, LEO Class, space situational awareness, carrying capacity, collision
avoidance, space sustainability.
1. Introduction
As low earth orbit (LEO) continues to become more
and more complex, the need for a robust and adaptive
framework to manage orbital traffic is becoming
increasingly critical. This paper proposes adopting an
orbital altitude-based "LEO Class" system modeled after
the aviation industry's Airspace Class approach to
address this necessity. The Airspace Class system in
