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Space traffic management (STM) is one of the most fashionable topics of contemporary space law and policy and the subject of countless studies. Nevertheless, there remains some confusion around the nature, scope and objectives of STM, with each study usually developing its own definition. Even the origins and historical developments of the concept are unknown to most experts. While the terminology and concept of STM are usually attributed to Dr Lubos Perek following his pioneering paper Traffic Rules for Outer Space presented at the 25^th International Colloquium on Space Law in Paris in 1982 [1,2], this article shows that the idea of regulating space traffic has been present and formalised since the early beginnings of space law, starting in the 1930s and becoming a widely debated topic in the 1950s and 1960s. Perek’s paper however provoked a revival of the concept, which was then recognised as a major issue of space law and policy research in the early 2000s.

Early considerations on space traffic rules

In 1932, when space travel was only the fruit of the imagination of inspired writers like J.-H. Rosny aîné and visionary scientists and engineers like Robert Esnault-Pelterie and Robert Goddard, Czechoslovak jurist Vladimir Mandl published Das Weltraum-Recht. Ein Problem Der Raumfahrt [3], often considered to be the first monograph on space law [4]. Expecting legal implications from the development of space activities, Mandl argued for the creation of a new field of law to complement existing air law regulations. In his overview of the legal challenges posed by astronautics, he mentioned for the first time the concept of “space traffic rules”, by extension of air traffic rules [3]. At the time, however, massive traffic in outer space was absolutely unimaginable and Mandl therefore described such rules as unnecessary [3].

At the peak of early space law and policy research in the 1950s and 1960s, there were numerous contributions on issues related to STM. In a 1957 article, Eugène Pépin identified five elements that would require the creation of “regulatory rule[s]” for “circulation” in outer space: (1) the ascension of rockets through sovereign airspace, (2) the re-entry of rocket bodies, (3) unintentional collisions between orbiting satellites, (4) the need for identification of satellites in case of accident and (5) the avoidance of harmful radio-interference [5]. The latter, electromagnetic interferences, have been the primary cause of concerns after the first satellite launches during the International Geophysical Year, and calls for regulations on this particular aspect of STM were made by most of the prominent space experts at the time [6–9]. Other proposals addressed more restricted issues such as launch areas and the “orientation of orbits” [7].

The first clear proposal of a set of rules was made by Perek in his Traffic Rules for Outer Space paper. These rules, although more detailed, roughly correspond to Pépin’s five elements presented in the previous section, with a noticeable addition being the mitigation of space debris [2]. However, such studies remained in the realm of theory until the need to define and actually implement traffic rules became tangible on 24 July 1996 when French military satellite Cerise was damaged by a piece of debris, making it “space’s first confirmed victim of a hit-and-run accident” [10].

The era of “Space Traffic Management” studies

The concept of space traffic, associated with the desire to manage it, made a real and definite comeback at the 5^th and 6^th International Space Cooperation workshops of the American Institute of Aeronautics and Astronautics (AIAA), held respectively in 1999 and 2001. By focusing on “orbital management, collision avoidance, relevant orbital debris issues, and regulatory framework needs” [11], they were the starting points of various initiatives such as the establishment of an STM working group at the International Academy of Astronautics (IAA), which produced the 2006 IAA Cosmic Study on Space Traffic Management [12].

However, increasing concerns about space traffic should not be explained solely by the visible initiatives of the AIAA, but also by the actual growth of space traffic as well as the emergence of the very closely related issue of space debris mitigation. In 2006, William H. Ailor claimed in a timely paper that “convergence on and formalization of a structure [for STM]” are contingent on three triggers: 1) a collision or interference involving a “major space asset”, 2) the growing fear of commercial satellite operators for the safety of their assets, and 3) the recognition of the space debris issue [13]. In fact, all three items of Ailor’s vision soon materialised in various forms: the Iridium-Kosmos collision [14]; the establishment of the Space Data Association by major satellite operators [15] – both in 2009; and the codification of various debris mitigation practices, such as the guidelines of the Inter-Agency Space Debris Coordination Committee (IADC) [16]. Finally, the surge of commercial interest in space in the last decade raises concerns about the safety and sustainability of the space environment. The number of objects in space is expected to increase dramatically in the next decade, primarily driven by the deployment of large constellations of satellites for broadband communication and by the development and spread of affordable small satellite technologies [17].

Thus, efforts should be made to preserve the outer space environment and the safety and sustainability of space operations. While these objectives are often what comes to mind when thinking of STM, there is a lot of confusion surrounding this concept in part due to the numerous definitions proposed over the years.

Defining space traffic management: a cumulative process

There is no authoritative nor widely accepted definition of STM. Rather, there are numerous studies proposing their own understanding of the concept, often framing it in relation to the underlying rationale of their argument or purpose. Without trying to be exhaustive, this section quotes and analyses a few key definitions to trace the evolution of the concept from the early 2000s onwards, with regards to the objectives, scope and nature of STM.

As one of the first attempts to clarify the roles and scope of STM, the definition presented during the two AIAA workshops identifies two core objectives of STM: space safety (“prevent damage in the near term”) and sustainability (“reduce the long-term potential for future damage”). Secondly, the scope of STM is defined as the whole lifecycle of the spacecraft, from “launch to disposal” [11,13]. However, it has two shortcomings: it restricts the objectives of STM to collision avoidance – although it was already part of Pépin’s list [5] – and it fails to define its potential nature. The former was addressed by Nicholas L. Johnson in 2004 when he identified as the aim of STM to “minimize the potential for electromagnetic or physical interference at any time” (emphasis added) [18], also adopting a more scientific wording in line with the statistical and probabilistic nature of space safety.

The first definition addressing the potential nature of STM can be found in the IAA study group’s Cosmic Study on STM, published in 2006:

Space traffic management means the set of technical and regulatory provisions for promoting safe access into outer space, operations in outer space and return from outer space to Earth free from physical or radio-frequency interference [12]

Its novelty was to define the nature of STM as the combination of an STM system, an ensemble of technical capabilities to enable space safety and sustainability, and of an STM regime, a set of institutional and regulatory elements. As the most widely accepted definition in the space community, it was left without modification in the IAA’s revised STM study released in 2018 [1]. The only potential criticism is the use of “radio-frequency interference”, instead of the preferable term of “electromagnetic interference” chosen by Johnson in particular [18].

Other later definitions, while retaining identical foundations, proposed variations on the overall structure of an STM framework. A 2020 report of the European Space Policy Institute (ESPI) suggested to divide STM into three “complementary functions”: space traffic monitoring (i.e. space situational awareness, or SSA), regulation (“principles, norms and rules”) and coordination (“stakeholders working together in an organised way”) [19]. Diametrically opposed to ESPI’s views, an August 2016 report of the Institute for Defense Analyses’ Science and Technology Policy Institute (IDA-STPI), a federally funded research centre supporting the White House Office of Science and Technology Policy, proposed to remove the technical aspects of the traffic issue – mostly SSA – from the scope of STM. Compared with their IAA colleagues, IDA-STPI experts envision STM primarily as a regime, and extract the previously mentioned ‘STM system’ as more or less SSA and associated technical capabilities [20]. Finally, the International Astronautical Federation’s STM Terminology Working Group went a step further than the IDA-STPI: in addition to separating SSA and STM, they proposed to differentiate between an STM regime focusing on safety issues (mostly composed of “space traffic coordination” norms and rules) and a “space environment preservation” regime dealing with long-term sustainability concerns (debris mitigation and remediation) [21].

Overall, the IAA definition appears to be the most comprehensive while flexible enough to be used as a reference in the literature. In particular, the distinction between what can be called an ‘STM regime’ and an ‘STM system’ (possibly separate from STM per se, following the IDA-STPI’s perspective) is useful as it allows the decoupling of two elements having different timelines and levels of priority. Most practitioners (e.g. government officials, satellite owner-operators) have serious doubts about the potential benefits of a comprehensive STM regime, such as those often proposed by international space law scholars, which may take decades to be established. On the other hand, the development of further technical capabilities for SSA is a matter of great urgency and can provide useful actionable data within a short timeframe.

Space traffic ménagement

While the expression of STM is commonly used in the space community, it can be argued that the wording of ‘management’ in relation to air and maritime traffic management is misleading. Practitioners reject the idea of management, which air and space law scholars usually relate to an overarching supranational structure for the actual control of activities in outer space. The Merriam-Webster dictionary defines the verb ‘to manage’ as “to handle or direct with a degree of skill: such as (a) to exercise executive, administrative, and supervisory direction of, (b) to treat with care, (c) to make and keep compliant” [22]. The Collins English Dictionary provides the following definition, supporting the idea of effective control inherent to the term of management: “management is the control and organizing of a business or other organization” [23]. None of these definitions corresponds to the nature of STM as usually discussed in space policy circles, that is to say focusing on the development of standards to facilitate communication among operators, the establishment of a voluntary-basis coordination framework, and the promotion of non-binding norms of behaviour. In fact, all successful outcomes of STM-related initiatives such as the UNCOPUOS Long-Term Sustainability guidelines, the IADC guidelines, or the Space Safety Coalition’s best practices, fall under the scope of ‘space safety promotion’ or ‘space traffic coordination’, rather than STM per se. As such, the most likely approach is one of ménagement rather than management, which in its original French meaning involves dealing with something or someone with care and consideration, which perfectly corresponds to the coordination spirit at the foundation of safe space operations [24].

About the Author

Quentin Verspieren is an assistant professor at the Science, Technology, and Innovation Governance (STIG) program of the University of Tokyo’s Graduate School of Public Policy and associate research fellow at the European Space Policy Institute (ESPI), where he researches space policymaking and technology development in developing countries, and international regime-making for space security, safety and sustainability. He has two master’s degrees in aerospace engineering (ISAE-SUPAERO and The University of Tokyo) and a Ph.D. in public policy (The University of Tokyo).

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