Towards Sustainable Satellite Swarms: MSc Aerospace Engineering Thesis

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.https://ieee-dataport.org/open-access/simulated-megaconstellation-ephemerides Starlink Constellation Position DataAerospace Engineerin

End-of-life of satellite swarms

Satellite swarms offer a high-capability mission architecture with a variety of potential applications in space exploration and discovery. Swarm-based architectures —which comprise multiple agents operating collectively as a distributed system— have been proposed for Earth observation, astronomy, planetary exploration, and heliophysics. Some of the key technology demonstration missions have already successfully flown in the past decades. The increasing interest in satellite swarms suggests that this innovative architecture will be adopted in a variety of future missions in the coming years, raising the question of how to dispose of satellite swarms at the end of their operational lifetimes. Mega-constellations or swarms comprising of numerous small satellites are difficult to track by Earth-based networks. They also increase the risk of collisions, particularly during end-of-life when these small satellites cannot be maneuvered to avoid collisions with functional satellite systems. Previously, distributed small satellite missions such as KickSat-2 and SpaceBEES 1-4 were designed to passively deorbit and burn up during atmospheric re-entry at the end of their lifetimes. However, disposing of satellite swarms outside low LEO (Low-Earth Orbit) has no trivial solution which both meets space situational awareness requirements and aligns with the philosophy of space sustainability. The distributed functionality which makes swarm missions so flexible and adaptable also means that many individual swarm agents have to be disposed of at end-of-life, rendering traditional approaches such as migration to the GEO (Geosynchronous Earth Orbit) graveyard orbit problematic. The challenges of disposing satellite swarms are as varied as the environments they could operate in — swarms used for planetary exploration will have to respect planetary protection policies while swarms engaged in Earth observation missions will have to be safely deorbited amidst an increasingly crowded LEO environment. In this paper we explore how the autonomy and distributed nature of swarms both complicates end-of-life disposal and simultaneously enables novel solutions to post-mission disposal. We then survey existing end-of-life scenarios for satellite swarms and propose a novel research approach to swarm disposal that could comply with both legal requirements and the philosophy of space sustainability.Signal Processing System

APIS: Applications and Potentials of Intelligent Swarms for magnetospheric studies

Earth's magnetosphere is vital for today's technologically dependent society. The energy transferred from the solar wind to the magnetosphere triggers electromagnetic storms on Earth, knocking out power grids and infrastructure - e.g., communication and navigation systems. Despite occurring on our astrophysical doorstep, numerous physical processes connecting the solar wind and our magnetosphere remain poorly understood. To date, over a dozen science missions have flown to study the magnetosphere, and many more design studies have been conducted. However, the majority of these solutions relied on large monolithic satellites, which limited the spatial resolution of these investigations, in addition to the technological limitations of the past. To counter these limitations, we propose the use of a satellite swarm, carrying numerous payloads for magnetospheric measurements. Our mission is named APIS - Applications and Potentials of Intelligent Swarms. The APIS mission aims to characterize fundamental plasma processes in the magnetosphere and measure the effect of the solar wind on our magnetosphere. We propose a swarm of 40 CubeSats in two highly-elliptical orbits around the Earth, which perform radio tomography in the magnetotail at 8-12 Earth Radii (R E) downstream, and the subsolar magnetosphere at 8-12 R E upstream. These maps will be made at both low-resolutions (at 0.5 R E, 5 seconds cadence) and high-resolutions (at 0.025 R E, 2 seconds cadence). In addition, in-situ measurements of the magnetic and electric fields, and plasma density will be performed by on-board instruments. In this publication, we present a design study of the APIS mission, which includes the mission design, navigation, communication, processing, power systems, propulsion and other critical satellite subsystems. The science requirements of the APIS mission levy stringent system requirements, which are addressed using Commercial Off-the-Shelf (COTS) technologies. We show the feasibility of the APIS mission using COTS technologies using preliminary link, power, and mass budgets. In addition to the technological study, we also investigated the legal considerations of the APIS mission. The APIS mission design study was part of the International Space University Space Studies Program in 2019 (ISU-SSP19) Next Generation Space Systems: Swarms Team Project. The authors of this publication are the participants of this 9-week project, in addition to the Chairs and Support staff. Electronic

Applications and Potentials of Intelligent Swarms for magnetospheric studies

Earth's magnetosphere is vital for today's technologically dependent society. To date, numerous design studies have been conducted and over a dozen science missions have flown to study the magnetosphere. However, a majority of these solutions relied on large monolithic satellites, which limited the spatial resolution of these investigations, as did the technological limitations of the past. To counter these limitations, we propose the use of a satellite swarm carrying numerous and distributed payloads for magnetospheric measurements. Our mission is named APIS — Applications and Potentials of Intelligent Swarms. The APIS mission aims to characterize fundamental plasma processes in the Earth's magnetosphere and measure the effect of the solar wind on our magnetosphere. We propose a swarm of 40 CubeSats in two highly-elliptical orbits around the Earth, which perform radio tomography in the magnetotail at 8–12 Earth Radii (RE) downstream, and the subsolar magnetosphere at 8–12 RE upstream. These maps will be made at both low-resolutions (at 0.5 RE, 5 s cadence) and high-resolutions (at 0.025 RE, 2 s cadence). In addition, in-situ measurements of the magnetic and electric fields, plasma density will be performed by on-board instruments. In this article, we present an outline of previous missions and designs for magnetospheric studies, along with the science drivers and motivation for the APIS mission. Furthermore, preliminary design results are included to show the feasibility of such a mission. The science requirements drive the APIS mission design, the mission operation and the system requirements. In addition to the various science payloads, critical subsystems of the satellites are investigated e.g., navigation, communication, processing and power systems. Our preliminary investigation on the mass, power and link budgets indicate that the mission could be realized using Commercial Off-the-Shelf (COTS) technologies and with homogeneous CubeSats, each with a 12U form factor. We summarize our findings, along with the potential next steps to strengthen our design study.Circuits and System