Towards Sustainable Satellite Swarms

Abstract

Satellite swarms are an emerging mission architecture which offer a flexible, robust alternative to traditional space missions. Drawing inspiration from naturally occurring swarms such as honey bees or ant colonies, satellite swarms consist of individual satellite agents working cooperatively towards a common goal. Distributed multi-agent space systems are, however, inherently problematic from the point of view of space sustainability. Given the increasingly likely prospect of operational satellite swarms, and considering that mitigating the build up of space debris is necessary to preserve our access to space and space-enabled services, the question of how to sustainably operate satellite swarms requires answering. This report presents two projects to explore how satellite swarms could be made more sustainable. In the first project we explored cooperative localisation in a satellite swarm. Using the well-studied Starlink satellite internet mega-constellation as a model swarm, we established the potential performance of cooperative localisation between 1584 Starlink satellites and 87 ground stations by calculating the Cramér-Rao Bound (CRB) at 573 simulated time steps. Our results show that the average Root Mean Square Error for localising the Starlink satellites has a constant value of approximately 10.15 m and varies between a maximum of 36.5 m and a minimum of around 2m. This result is determined primarily by the geometry of the Starlink mega-constellation and the characteristics of the inter satellite links, and gives values comparable to GNSS hardware currently on satellites. The values are also in agreement with previous research. In the second project, we introduce a satellite health indicator, a composite indicator capturing the health of a swarm satellite. We also present ongoing research modelling swarm satellites with Markov chains using CubeSat subsystems as a basis for the subsystems of swarm satellites. We also present an analysis of historical CubeSat failures using data from the CGEE CubeSat database, which shows that 18.1% of all CubeSats launched currently present a risk to space sustainability. We conclude both projects with a discussion of next steps and future research in these emerging topics.