Real-time air-traffic warning during satellite re-entries: Challenges and developments

Abstract

Over time, new market trends are shaped by advances in technological development. The space sector is no exception to this evolution, with launches across all mass and type classes reaching record levels in recent years. In terms of re-entries, this translates into a rapid increase in the number of re-entering objects. Between 10 % and 40 % of the re-entering mass is expected to survive, posing a potential hazard to aircraft, ships and ground populations. Alongside to the uncertainty on the surviving mass, the on-ground risk assessment is still strongly affected by the uncertainties in predicting the re-entry point, which is estimated around 20 % of the remaining lifetime for an uncontrolled re-entry from a circular orbit. Despite these challenges, the theory for the on-ground risk assessment is in a certain extent harmonised within the international context of space agencies. In contrast, the assessment of the risk that re-entering objects pose to air and sea traffic is still a major point of discussion today, with methodologies that can vary widely from one country/agency/entity to another. This paper discusses key challenges that are currently hindering the implementation of real-time air traffic warnings during Earth's atmospheric re-entries, ranging from technical gaps to the lack of clear metrics or a centralised coordination point, and outlines recent developments aimed at mitigating these issues. The first section of this work provides an overview of relevant historical events and comments the international response to the increased risk, while the second section discuss the challenges for the practical implementation of a real-time risk assessment for air traffic during the re-entry of space objects, and propose near-term steps for a overcoming them.