Expanding LEO Capacity Through Orbital Classification Frameworks

Low Earth Orbit (LEO) is an increasingly complex domain, challenging its international governance framework. Decades of work to improve safety in orbit have focused on the ongoing issue of orbital debris, but the emerging challenges posed by the growth in large constellations and increasing demand for space services necessitate the consideration of new policy-based frameworks. International fora, like the Inter-Agency Space Debris Coordination Committee (IADC), have produced consensus guidelines for the mitigation of space debris. This model illustrates that harmonized approaches may be available to address common concerns of space safety. The IADC’s first internationally adopted guidance document, the “IADC Guidelines,” was presented to the Scientific and Technical Sub Committee (STSC) of the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) in 2003 as part of the official work program and was endorsed by the UN General Assembly in December of 2007. The guideline approach used by IADC to address the issue of space debris can provide a roadmap for the development of an orbital classification framework to facilitate the safe expansion of orbital capacity in LEO. This paper suggests a policy-based approach to performance requirements for active space objects in described orbits based on definable risk metrics. Orbital 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. A policy-based framework that establishes guidelines for minimum entry requirements for particular orbits reduces the inadvertent capacity effects of least capable actors. While space debris remains a pressing issue for space safety, rapid growth in the number of objects in LEO and corresponding projections for increasingly dramatic future growth have drawn attention to the question of orbital carrying capacity. Researchers are examining how orbital carrying capacity should be defined and quantified. Various approaches, like the Space Environment Capacity Concept, are emerging. The panoply of available approaches can be filtered by how we collectively consider the problem of orbital capacity. Do we consider that there is a finite number of objects that a particular orbit can accommodate, and therefore, growth must be constrained to prevent over-exploitation? Or do we consider that growth is both inevitable and desirable, and we should consider policy choices that seek to increase available capacity to ensure the safety and sustainability of LEO? This paper assumes the latter and presents a potential framework derived from the aviation experience of airspace capacity, using an orbital classification approach to create guidelines for entry requirements for operations in and transits through defined altitudes based on congestion and collision risk [Figure 1]. These guidelines could assist both operators and States in the development and approval of space missions. This work builds on the emergent behaviors of space operators in high-density or high-risk orbits to codify a framework of best practices organized under a globally harmonized model that is well-known and accepted in the aviation domain. The orbital classification concept is a first step designed to facilitate the work of experts in defining the orbital bands with common risk characteristics and identifying the entry requirements and external elements (i.e., available SSA performance) appropriate to mitigate the risk of increased activity. This paper relies on the experience of the aviation community in developing airspace classification as a tool to increase both airspace capacity and safety but recognizes the distinct differences in both the physical characteristics and governance structures of the aviation and space domains.