Exploring the Feasibility of Detecting LEO Space Objects in Passive Radar Without Prior Orbit Parameter Information

One of the crucial factors allowing the passive observation of Low-Earth Orbit (LEO) objects is the compensation of their motion. Previous authors' research assumed that the information about orbital parameters of the considered object, and consequently its approximate trajectory, are known. This paper presents the results of studies on the possibility of detecting space objects moving in LEO using passive radar without the knowledge of their orbital parameters. Apart from theoretical considerations, the results of real-life experiments are discussed. The experiments were performed using the astronomical LOw-Frequency ARray (LOFAR) radio telescope as a surveillance receiver of the passive radar system, and terrestrial commercial digital radio transmitters operating in the VHF band employed as an illuminator of opportunity. The large antenna array of the LOFAR radio telescope enables receiving very weak echo signals reflected from LEO objects. The results of the experiments confirm the feasibility of observation of the selected fragment of space and detection of the LEO objects moving in this fragment of space without knowledge of their orbital elements, which are usually given in the Two-Line Element (TLE) format.