Beamforming of LOFAR Radio-Telescope for Passive Radiolocation Purposes

Aleksander Droszcz,Julia Kłos,Konrad Jędrzejewski,Krzysztof Kulpa,Mariusz Pożoga

doi:10.3390/rs13040810

Aleksander Droszcz, Julia Kłos + Show 3 more

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https://doi.org/10.3390/rs13040810

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Abstract

This paper presents the results of investigations on the beamforming of a low-frequency radio-telescope LOFAR which can be used as a receiver in passive coherent location (PCL) radars for aerial and space object detection and tracking. The use of a LOFAR radio-telescope for the passive tracking of space objects can be a highly cost-effective solution due to the fact that most of the necessary equipment needed for passive radiolocation already exists in the form of LOFAR stations. The capability of the radiolocation of planes by a single LOFAR station in Borowiec is considered to be ‘proof of concept’ for future research focused on the localization of space objects. Beam patterns of single sets of LOFAR antennas (known as tiles), as well as for the entire LOFAR station, are presented and thoroughly discussed in the paper. Issues related to grating lobes in LOFAR beam patterns are also highlighted. A beamforming algorithm used for passive radiolocation purposes, exploiting data collected by a LOFAR station, is also discussed. The results of preliminary experiments carried out with real signals collected by the LOFAR station in Borowiec, Poland confirm that the appropriate beamforming can significantly increase the radar’s detection range, as well as the detection’s certainty.

Highlights

LOw-Frequency ARray for radio astronomy (LOFAR) is an international network of multi-antenna radio-telescopes operating at low frequencies that was constructed and designed by the Dutch astronomical agency ASTRON, the NetherlandsInstitute for Radio Astronomy
The results of the preliminary experiments confirmed that application of the beamforming algorithm can significantly increase the capabilities of the passive radiolocation system based on a LOFAR station as the receiver
The comparison of the estimated target parameters with results calculated on the basis of data delivered by the application flightradar24 shows the relatively high accuracy of the estimation of target parameters, i.e., range, velocity, and azimuth, the methods used for their calculation were basic

Summary

Introduction

LOw-Frequency ARray for radio astronomy (LOFAR) is an international network of multi-antenna radio-telescopes operating at low frequencies (below 250 MHz) that was constructed and designed by the Dutch astronomical agency ASTRON, the Netherlands. The main scientific goal of the construction of LOFAR was to create opportunities for the observation of the epochs of reionization, deep extragalactic surveys, transient radio phenomena, pulsars, ultra high-energy cosmic rays, cosmic magnetism, solar physics, and space weather [2]. This paper is devoted to a new idea of the use of a LOFAR station and its beamforming for passive radiolocation purposes, and is an extension of a paper originally presented in 2020 at the 21st International Radar Symposium (IRS) [3].

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