Resident Space Object Orbit Determination Using a Multireceiver Radar System

The increasing in-orbit population of resident objects is currently fostering many Space Surveillance and Tracking (SST) initiatives. Italy contributes to the EUSST (European SST) initiative with the BIstatic RAdar for LEo Survey (BIRALES), whose transmitter is the Radio Frequency Transmitter, located at the Italian Joint Test Range of Salto di Quirra in Sardinia, and whose receiver is a portion of the Northern Cross Radio Telescope, located at the Medicina Radio Astronomical Station, near Bologna. In order to perform orbit determination (OD) from BIRALES observations, the receiver raw data shall be properly processed, such that angular profiles are correctly reconstructed. In this framework, this work proposes the Music Approach for Track Estimate and Refinement (MATER) algorithm. First, the signal direction of arrival (DOA) is estimated with the MUltiple SIgnal Classification (MUSIC) technique, which exploits the signal covariance matrix. For catalogued objects, the available ephemerides can be exploited in the DOA estimation process to save computational time and to avoid ambiguity in the solution. For uncatalogued objects, multiple track candidates occur due to the intrinsic array ambiguity. In order to solve such an ambiguity, all candidates enter an initial OD process. Consequently, multiple orbits are reconstructed, and their probabilistic correlation indexes are computed. The correct track is selected as the one corresponding to the orbit featuring the best index. MATER is first tested on a synthetic dataset of 899 LEO passages. The algorithm converges to the correct solution in 100% both for catalogued and uncatalogued objects. The obtained angular accuracy is in the order of 1e-4 deg. In addition, the performance of MATER on a challenging real scenario is presented.