Novel Interferometric Techniques for Detecting the 21-cm Signal from the Epoch of Reionisation

Detecting the cosmological 21-cm signal from the Epoch of Reionisation (EoR) presents a significant challenge due to foreground contamination and instrumental limitations. Therefore, alternative approaches can be explored to overcome some of these challenges. This work presents two independent approaches: Lunar Occultation for estimating the global 21-cm signal and closure phases for measuring the 21-cm power spectrum. Lunar Occultation utilises the Moon as a thermal reference to measure the foreground sky temperature, with results demonstrated using Murchison Widefield Array (MWA) observations. A key aspect of this method is mitigating reflected FM Radio Frequency Interference (RFI) from the Moon, which is addressed through modelling and statistical techniques. The second method employs radio interferometric closure phases to estimate the 21-cm power spectrum, providing a calibration-independent alternative to traditional visibility-based methods. Our analysis of MWA data reveals systematic contaminants that impact sensitivity, which are mitigated using statistical techniques. These methods lay basic foundation which can be beneficial for the upcoming radio experiments, especially SKA-low, to further our understanding of the early Universe through the 21-cm signal.

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