PhD Studentship: Collision Risk Assessment and Mitigation for Large Constellations of Satellites

University of Southampton - Astronautics, Faculty of Engineering and the Environment

Satellites provide services that are used by an increasingly wide and diverse range of users but they occupy an environment that is congested and contested. These issues, and the growth of the space debris population, influence the safety and sustainability of spaceflight. Recent research has focused on the development of large constellations of satellites that will operate in low Earth orbit. These constellation systems will produce a step-change in the amount of space traffic and a similar change in the complexity of space traffic management. One aspect of particular concern is the predicted increase in the number of close approaches involving satellites or space debris as a result of the increase in traffic. Constellation operators will likely be faced with a large number of close approaches and will need to make informed decisions about collision avoidance manoeuvres. Based on observations from existing constellations, which comprise fewer satellites than the systems that are in development, large constellations will need to determine the best trade-off between the safety of their satellites and the need for continuity of the service they will provide. In other words, the operators will need to accept a certain level of collision risk in order to reduce the number of collision avoidance manoeuvres that would remove the satellite from service temporarily. An investigation of how to optimise this trade-off will be a key objective of the PhD research. On the face of it, the trade-off appears to be relatively straightforward. However, the majority of constellations under development intend to use low-thrust propulsion systems for their satellites. This means that the methods typically used to understand collision risk may not be appropriate: decisions about manoeuvres will need to take place with increased lead times to allow for the slow change in orbits, meaning that the uncertainty in predictions of satellite positions will be higher. Incorporating these factors in the trade-off described above will lead to a relatively complex prediction and optimisation problem, with scope for some novel and meaningful contributions towards the safe and sustainable use of space.

The project will be a collaborative effort between the University of Southampton and the UK Space Agency, with opportunities for placements at the Agency throughout the project.

The ideal candidate will have a degree in an engineering, science or mathematics discipline, preferably with some experience of the space environment, astronautics or spacecraft engineering. Applications from highly motivated individuals with this background, and having good project and time management skills, are encouraged. The successful candidate will work alongside a team of 20 postgraduate researchers in the Astronautics Research Group.

If you wish to discuss any details of the project informally, please contact Dr Hugh Lewis, Astronautics research group, Email:, Tel: +44 (0) 2380 59 3880.

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