Tomographic Reconstruction of Volcanic Ash Plumes Using Simulated Satellite Image Data

  • Thomas Etchells

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Volcanic ash suspended in the atmosphere can pose significant hazards. Ash can cause acute health impacts to humans over tens to hundreds of kilometres from a volcanic eruption, and potential damage to aircraft engines over thousands of kilometres. Most monitoring and forecasting of ash contaminated airspace is performed using two-dimensional satellite image data. Some limited three-dimensional image data is available, providing useful plume property information such as cloud top heights. Full three-dimensional reconstructions of volcanic ash clouds would thus provide a unique new perspective, aiding the monitoring and forecasting of ash contaminated airspace.

Additionally, the multi-spectral infrared observation of volcanic ash clouds can retrieve quantitative information such as line-of-sight ash mass loading through a plume. This information, combined with three-dimensional observations, would allow the tomographic reconstruction of a volcanic ash plume, retrieving the internal structure and concentration distributions within the plume. This thesis presents work investigating the feasibility of the three-dimensional tomographic reconstruction of volcanic ash plumes using satellite image data, particularly with reference to the increasingly popular domain of `Small Satellites'.

To approach this, the work was divided into two initial investigations. The first investigated the feasibility of three-dimensional reconstruction of volcanic ash plumes when considering the limited viewing angles available to an orbiting remote sensing satellite. Orbital simulations were used to provide realistic orbital viewing geometry. This geometry was then used as an input to generate simulated satellite image data of a volcanic plume. This simulated image data was used to perform and evaluate the reconstruction of the surface hull of the target plume. Thresholds and suggestions for the viewing geometry such as the amount of image data and its angular distribution were identified.

Following this is a second investigation into the tomographic reconstruction of a volcanic ash cloud, assuming idealised observation geometry. A semi-realistic plume simulation environment was developed to generate image data analogous to the line-of-sight mass loadings provided by multi-spectral infrared retrievals. This image data was used to perform and evaluate initial tomographic reconstructions of a simulated target ash plume. Suggestions for limitations and requirements for imaging properties such as pointing accuracy and spatial sampling distances were identified.

The two previous investigations were then combined to evaluate the tomographic reconstruction of volcanic ash plumes using multi-angle and multi-spectral infrared satellite image data. The simulations and results presented in the thesis are given context by reference to the Pointable Radiometer for Observation of Volcanic Emissions (PROVE) CubeSat, a multi-spectral remote sensing satellite concept being developed by the University of Bristol Satellite (UoBSat) team. Suggestions for some design requirements for the satellite are presented.
Date of Award23 Jan 2024
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorLucy Berthoud (Supervisor), I M Watson (Supervisor) & Andrew Calway (Supervisor)

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