We have extended our previous work to use the Murchison widefield array (MWA) as a non-coherent passive radar system in the FM frequency band, using terrestrial FM transmitters to illuminate objects in low Earth orbit (LEO) and the MWA as the sensitive receiving element for the radar return. We have implemented a blind detection algorithm that searches for these reflected signals in difference images constructed using standard interferometric imaging techniques. From a large-scale survey using 20 h of archived MWA observations, we detect 74 unique objects over multiple passes, demonstrating the MWA to be a valuable addition to the global Space Domain Awareness network. We detected objects with ranges up to 977 km and as small as $0.03$ ${\rm m}^2$ radar cross section. We found that 30 objects were either non-operational satellites or upper-stage rocket body debris. Additionally, we also detected FM reflections from Geminid meteors and aircraft flying over the MWA. Most of the detections of objects in LEO were found to lie within the parameter space predicted by previous feasibility studies, verifying the performance of the MWA for this application. We have also used our survey to characterise these reflected signals from LEO objects as a source of radio frequency interference (RFI) that corrupts astronomical observations. This has allowed us to undertake an initial analysis of the impact of this RFI on the MWA and the future square kilometer array (SKA). As part of this analysis, we show that the standard MWA RFI flagging strategy misses most of this RFI and that this should be a careful consideration for the SKA.

中文翻译：

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使用非相干无源雷达和默奇森宽场阵列对低地球轨道环境进行低频盲测

我们扩展了我们之前的工作，将默奇森宽场阵列 (MWA) 作为 FM 频带中的非相干无源雷达系统，使用地面 FM 发射器照亮低地球轨道 (LEO) 中的物体，并将 MWA 作为敏感接收雷达回波元件。我们已经实现了一种盲检测算法，该算法在使用标准干涉成像技术构建的差异图像中搜索这些反射信号。从使用 20 小时存档 MWA 观测的大规模调查中，我们在多个通道中检测到 74 个独特的物体，证明 MWA 是全球空间领域意识网络的宝贵补充。我们检测到的物体范围可达 977 公里，小至 $0.03$ ${\rm m}^2$ 雷达截面。我们发现 30 个物体要么是非运行卫星，要么是火箭上层碎片。此外，我们还检测到双子座流星和飞行在 MWA 上的飞机的 FM 反射。发现 LEO 中的大多数物体检测都位于先前可行性研究预测的参数空间内，从而验证了 MWA 在此应用中的性能。我们还利用我们的调查将这些来自 LEO 天体的反射信号表征为破坏天文观测的射频干扰 (RFI) 源。这使我们能够对该 RFI 对 MWA 和未来平方公里阵列 (SKA) 的影响进行初步分析。作为该分析的一部分，