Adaptive track estimation on a radar array system for space surveillance

The increasing population of resident space objects is currently fostering many Space Surveillance and Tracking(SST) initiatives, which are based on the use of ground sensors. Italy contributes to the European SST SupportFramework with the BIstatic RAdar for LEo Survey (BIRALES). Orbit determination from BIRALES observationsrelies on the estimation of the angular profiles of the object crossing the sensor field of view by processing thereceiver raw data. Based on the receiver array configuration, its field of view is currently populated with manyindependent beams. However, the results of the currently adopted orbit determination process are negativelyaffected by the simultaneous presence of multiple grating lobes in the receiver gain pattern and by the signalquality. Within this context, this work proposes a paradigm shift in BIRALES data processing by introducing amultiple signal classification (MUSIC) approach. First, in the track estimation phase, multiple signal directionsof arrival are determined, at any time instant, from the data correlation matrix. The multiplicity of the solutionsis due to the array geometry and yields ambiguity in track reconstruction. For the catalogued objects, thisambiguity can be solved by exploiting the availability of their orbital estimates. For the uncatalogued ones, itis solved by clustering the candidate signal directions of arrival and identifying the correct track using slantrange, Doppler shift and signal to noise ratio measurements. Although introduced for BIRALES, the applicabilityof the method extends to any SST survey radar with an array receiver and with the ability to correlate thesignals detected by each receiver element. Finally, algorithm performances and robustness are assessed on alarge set of synthetic passes as well as on real measurements.