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Permittivity reconstruction and radio-propagation simulations to guide sub-surface radar exploration of ice moons and terrestrial glaciers for the Enceladus [...] / Alexander Luke Kyriacou. Wuppertal, 2023
Content
Introduction
Modelling Radio Propagation in Ice
In-situ measurement of ice permittivity
Enceladus: A home for extraterrestrial life?
Observational History
Orbital Characteristics
Geology
Internal Structure
Origin and Geological History
Surface Features
South Polar Terrain
Tiger Stripes and Geysers
Plumes
Astrobiological Potential
Future Exploration
Enceladus Explorer - AsGAr
Enceladus Explorer (EnEx)
Mission Outline
Mission Architecture
Combined Spacecraft
Orbiter
Lander
IceMole
Field Tests
Sub-projects
EnEx-AsGAr
Radar Exploration
Permittivity Reconstruction
Summary
Radar Simulations with Parabolic Equation Methods
Introduction
Modelling Electromagnetic Waves in Ice
Finite Difference Time Domain
Ray Tracing
Parabolic Equations
Numerical Spatial Solution in Frequency Domain
Time Domain Solution
Backwards Propagation
Example of two-way PE simulation
Simulations through Glaciers with data-defined profiles
Examples of Glaciers
Frequency Domain
Time Domain
Limitations and Potential Improvements to PE Methods
Inversion of PE Simulations using Genetic Algorithms
Genetic Algorithms
Examples of GAs
GA Procedure
GA-based Inversion of paraProp
Misfit and Fitness Function
Initialization
Genetic Operators
Selection
Testing with Pseudo-Data
Signal Settings and Antenna Positions
Ref-Index Scenarios
RF Simulation Setup
GA Settings
Results
Discussion
Limitations of Inversion
Limitations of GAs
Cross-Borehole Permittivity Radar
Modulation Technique
Frequency Modulated Continuous Wave (FMCW) Radar
Design
Layout
Electronics
Antenna
Control: Permittivity Measurement Mode
Transmitter: TX
Receiver: RX
Measurement Procedure
Data Acquisition
Processing
Testing of Permittivity Radar
PLL Tests
Antenna Tests
In-Air Antenna Transmission Tests
Summary of System
Experimental Uncertainties
Field Campaign at the Aletsch Glacier
Goals of the Field Test
Location and Timeline
Aletsch Glacier
Site Plan
Cross-Borehole Measurements
Parallel Depth Profiles
Cross Depth Profiles
Permittivity estimation via Peak Analysis Method
Results: Permittivity Profile
Attenuation Measurement
Summary
Analysis of Field Test Data
Glacier Modelling
Comparison of Field Test with RT and PE Simulations
RT Simulation
PE Simulation
Simulation Results
Reconstruction of the Refractive Index profile with PEs
Simulating the transmitted signal
Settings
Results
Discussion
Summary of GA reconstruction
Conclusions
Summary of Results
Simulating radio-wave propagation through ice
In-situ measurements of ice permittivity
Future Work
Parabolic Equation Simulations
Inversion of PE and RT simulations
Permittivity Radar
Use of Permittivity Radar in Field Tests
Appendices
Dielectric Properties of Ice
Permittivity: Theory
Atomic Model
Debye Model
Formation of Glacial Firn
Densification
Densification Models
Melting and Refreezing
The Permittivity Profile of the Tiger Stripe Region
Ice Deposition on a Global Scale
Geyser deposition modeling
Results for Deposition
Sintered snow layer
Ice Deposition on a Local Scale
Permittivity Profile
Layering
Chemical Composition
Discussion
Conclusions
Field Test 1
Field Test 1: Mittelbergerferner
Results
Comparison of PEs to FDTD
Non-Flat Surface Simulations with paraProp
Non-flat Surfaces
Example: Brueggen glacier