Outer space is increasingly central to international security. The use of Starlink in the Russo–Ukrainian war has enabled Ukrainian operations while negating Russian interference. Having witnessed Starlink’s crucial impact in Ukraine, several states seek to emulate the system’s offensive and defensive advantages. This article analyses how the onset of mega-constellations – satellite systems consisting of very high numbers of smaller satellites – will affect stability in the space domain. As states are increasingly dependent on space for both nuclear and conventional operations, the stability of the space domain is a key concern for international security. Showing how mega-constellations can mitigate existing vulnerabilities in space while generating offensive advantages on earth, this article shows that their proliferation is likely to make conventional counterspace attacks ineffective and costly. Therefore, mega-constellations will have a stabilising effect between states equally dependant on space. However, under conditions of asymmetric dependence, less space-reliant states may find incentives to employ highly destructive weapons, including nuclear weapons, to disable adversary mega-constellations. Accordingly, the proliferation of mega-constellations may act in a destabilising manner, especially if under conditions of asymmetry in space.

As the number of large Earth-orbiting satellite networks (i.e., mega-constellations or mega-sats) increases, so does the threat posed to astronomical research. Bright satellite trails in exposures of the night sky can affect the quality of observations and hinder science objectives. Using the MASCARA station to detect satellites from the SpaceX Starlink network as a representative case, this study quantifies the present and future impact of mega-sats on ground-based optical astronomy. We find that further design revisions are required to mitigate the brightness concern of pre-Gen2 Starlinks and that hundreds of satellites could be visible in all-sky observations at peak observing times if additional measures are not taken.

This paper presents an overview of the attitudes and awareness within the amateur astronomical community regarding modern satellite megaconstellation projects. A series of interviews and polls to assess the perspectives of this large community was conducted, aiming to uncover their concerns and issues. Additionally, the potential to involve respondents in community-driven projects focused on satellite data acquisition and processing was investigated. The objective is to enhance data quality for astronomical imagery protection and improve existing tools for scientific research, including satellite tracking, trajectory prediction, and the detection of space debris and orbital objects.