The development of non-coherent passive radar techniques for space situational awareness with the Murchison Widefield Array

Abstract

The number of active and non active satellites in Earth orbit has dramatically increased in recent decades, requiring the development of novel surveillance techniques to monitor and track them. In this paper, we build upon previous non-coherent passive radar space surveillance demonstrations undertaken using the Murchison Widefield Array (MWA). We develop the concept of the Dynamic Signal to Noise Ratio Spectrum (DSNRS) in order to isolate signals of interest (reflections of FM transmissions of objects in orbit) and efficiently differentiate them from direct path reception events. We detect and track Alouette-2, ALOS, UKube-1, the International Space Station, and Duchifat-1 in this manner. We also identified out-of-band transmissions from Duchifat-1 and UKube-1 using these techniques, demonstrating the MWA's capability to look for spurious transmissions from satellites. We identify an offset from the locations predicted by the cataloged orbital parameters for some of the satellites, demonstrating the potential of using MWA for satellite catalog maintenance. These results demonstrate the capability of the MWA for Space Situational Awareness and we describe future work in this area.

A low-frequency blind survey of the low Earth orbit environment using non-coherent passive radar with the Murchison widefield array

“…All of the detected objects in this work (except three CubeSats and one MiniSat) were detected within the theoretically predicted parameter space. Two of the CubeSats (DUCHIFAT-1 and UKUBE-1) were detected due to out-of band transmissions in the FM band (as previously observed by Zhang et al 2018 andPrabu et al 2020b) and the other CubeSat and MiniSat were detected through FM reflections. Some satellites such as the ISS and Hubble Space Telescope (HST) were also detected outside the MWA's primary beam due to their large RCS.…”

“…Previously, Prabu et al (2020b) demonstrated the so-called dynamic signal to noise ratio spectrum (DSNRS) technique, detecting signals from satellites/debris, either via FM reflections or downlink transmissions, and differentiates them from other types of radio frequency interference (RFI) entering the detection system (the MWA). This previous work utilised the results of Zhang et al (2018) to select a small set of MWA observations known to contain signals reflected from satellites.…”

“…The MWA can observe the sky at 70-300 MHz and was primarily designed for radio astronomy purposes (Bowman et al 2013;Beardsley et al 2019). The MWA has detected satellites in the past using two different techniques, namely coherent detection (Palmer et al 2017;Hennessy et al 2019) and non-coherent detection (Tingay et al 2013b;Zhang et al 2018;Prabu et al 2020b) methods.…”

“…The coherent detection method uses the MWA's high time and frequency resolution voltage capture system (VCS) (Tremblay et al 2015) and performs detections using matched filters designed using the transmitted FM signal (Hennessy et al 2019), while the non-coherent detection system uses interferometer correlated data (Prabu et al 2020b) along with wide-field imaging techniques. The blind detection pipeline developed here uses the non-coherent detection method, including the use of the DSNRS techniques established by Prabu et al (2020b).…”

A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory

“…At these frequencies, as well as ducted propagation from distant transmitters, multi-path reception of RFI is expected due to reflections of objects within the environment. For example, reflections of aircraft (Wilensky et al 2020), ionised meteor trails (Zhang et al 2018), and satellites (Prabu et al 2020b;Zhang et al 2018;Tingay et al 2013b) are expected. Such signals are ubiquitous and have been studied in detail for other low frequency radio telescopes such as the Owens Valley Long Wavelength Array (Monroe 2018).…”