Investigating the use of ray tracing for signal-level radar simulation in space monitoring applications: a comparison of radio propagation models

Doctoral Thesis


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This thesis presents the design and development of an accelerated signal-level radar simulator with an emphasis on space debris monitoring in the Low Earth Orbit. Space surveillance represents a major topic of concern to astronomers as the threat of space debris and orbital overpopulation looms – particularly due to the lack of effective mitigation techniques and the limitations of modern space-monitoring sensors. This work thus aimed to investigate and design possible tools that could be used for training, testing and research purposes, and thereby aid further study in the field. At present, there exist no three-dimensional, ray-traced, signal-level radar simulators available for public use. As such, this thesis proposes an open-source, ray-traced radar simulator that models the interactions between spaceborne targets and terrestrial radar systems. This utilises a ray-tracing algorithm to simulate the effects of debris size, shape, orientation, and material properties when computing radar signals in a typical simulation. The generated received signals, produced at the output of the simulator, were also verified against systems theory, and validated with an existing, well-established simulator. The developed software was designed to aid astronomers and researchers in space situational awareness applications through the simulation of radar designs for orbital surveillance experiments. Due to its open-source nature, it is also expected to be used in training and research environments involving the testing of space-monitoring systems under various simulation conditions. The software offers native support for measured Two-Line Element datasets and the Simplified General Perturbations #4 orbit propagation model, enabling the accurate modelling of targets and the dynamic orbital forces acting upon them. As a result, the software has aptly been named the Space Object Astrodynamics and Radar Simulator – or SOARS. SOARS was built upon the foundations of a general-purpose radar simulator known as the Flexible Extensible Radar Simulator – or FERS – which provided integrated radar models for propagation loss, antenna shapes, Doppler and phase shifts, Radar Cross Section modelling, pulse waveforms, high-accuracy clock mechanisms, and interpolation algorithms. While FERS lacked various features required for space-monitoring applications, many of its implementations were used in SOARS to minimise simulation limits and maximise signal rendering accuracy by supporting an arbitrary number of transmitters, receivers, and targets. The goal was thus to have the simulator limited only by the end-user's system, and to specialise the operation of the software towards space surveillance by integrating additional features – such as built-in models for environmental and system noise, multiscatter effects, and target modelling using meshes comprised of triangular primitives. After completing the software's development, the ray-traced simulator was compared against a more streamlined version of SOARS that made use of point-model approximations for quick-look simulations, and the trade-offs between both simulators (including software runtime, memory utilisation and simulation accuracy) were investigated and evaluated. This assessed the value of implementing ray tracing in a radar simulator operating primarily within space contexts and evaluated the results of both simulators using detection processing as a demonstrated application of the system. And while the use of ray tracing resulted in significant costs in speed and memory, the investigation found that the ray-traced simulator generated more reliable results relative to the point-model version – providing various advantages in test scenarios involving shadowing and multiscatter. The design of the SOARS software, as well as its point-model “baseline” alternative and the investigation into each simulator's advantages and disadvantages, are thus presented in this thesis. The developed programs were released as open-source tools under the GNU General Public Licence and are freely available for public use, modification, and distribution.