Micro-Doppler signatures and object characterisation of space debris with radio telescopes

This study presents a novel multi-static radar technique for space debris characterisation using micro-Doppler signatures, developed within the Southern Hemisphere Asteroid Radar Programme (SHARP). The method employs C-band continuous waveforms transmitted from NASA's Deep Space Network (DSN) Canberra station, with reflected signals captured by distributed ground-based telescopes converted from astronomical to radar operations. From March 2021 to September 2025, we conducted systematic observations of 20 distinct rocket bodies at various orbital altitudes and object sizes. Micro-Doppler analysis of axial rotation signatures enabled extraction of rotation periods, object dimensions, surface characteristics, and mass distribution parameters with enhanced accuracy in orbital refinement. We implemented advanced imaging reconstruction techniques to generate morphology data of the targets. Results demonstrate successful determination of debris rotation periods with second-level precision, dimensional estimates within 10\% accuracy compared to known specifications, and improved orbital parameter determination reducing position uncertainties by up to 30\%. The technique provides a cost-effective approach for space situational awareness, leveraging existing astronomical infrastructure to enhance Australia's sovereign capabilities in tracking both near-Earth objects and space debris. This multi-static configuration offers significant advantages over traditional monostatic radar systems for geostationary and highly elliptical orbit debris monitoring.