Analysis of the Potential for Using Over-The-Horizon Radar Systems for Space Surveillance

The Australian Defence Force is investigating the development of a space surveillance system. While several dedicated facilities for space surveillance are in operation around the world, Australia's Over-The-Horizon Radar (OTHR) network has some potential for this role. The OTHR operates in the HF band and is constrained by the propagation effects of the ionosphere. A spherically stratified ionospheric model and a model for a nominal OTHR antenna are developed that allow calculation of path propagation, power distribution, and clutter returns. A software-based radar receiver processing system is modeled to determine detection probabilities and the minimum detectable radar cross-section of targets in typical low earth orbit (LEO) trajectories. The high clutter power levels, coupled with long target ranges and high velocities, mean that range-Doppler tradeoffs have a great impact on the resulting detection capabilities. While the system as modeled has the potential to provide some coverage for LEO targets, operational constraints mean the necessary conditions for detection of space targets would rarely be met while the system is involved in traditional OTHR tasking. Further, the long wavelengths and large antenna beams mean the accuracy of any positioning information is low.