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We present the first of two papers dedicated to verifying the Australian Epoch of Reionisation pipeline (AusEoRPipe) through simulation. The AusEoRPipe aims to disentangle 21-cm radiation emitted by gas surrounding the very first stars from contaminating foreground astrophysical sources, and has been in development for close to a decade. In this paper, we build an accurate 21-cm sky model that can be used by the WODEN simulation software to create visibilities containing a predictable 21-cm signal. We verify that the power spectrum estimator CHIPS can recover this signal in the absence of foregrounds. We also investigate how measurements in Fourier-space are correlated, and how their gridded density affects the power spectrum. We measure and fit for this effect using Gaussian-noise simulations of the MWA phase I layout. We find a gridding density correction factor of 2.651 appropriate for integrations equal to or greater than 30 minutes of data, which contain observations with multiple primary beam pointings and LSTs. Paper II of this series will use the results of this paper to test the AusEoRPipe in the presence of foregrounds and instrumental effects., Comment: 13 pages, 11 Figures, 1 table, accepted in the Publications of the Astronomical Society of Australia (PASA)

The cosmological 21cm signal offers a potential probe of the early Universe and the first ionizing sources. Current experiments probe the spatially-dependent variance (Gaussianity) of the signal through the power spectrum (PS). The signal however is expected to be highly non-Gaussian due to the complex topology of reionization and X-ray heating. We investigate the non-Gaussianities of X-ray heating and reionization, by calculating the skew spectrum (SS) of the 21cm signal using MERAXES, which couples a semi-analytic galaxy population with semi-numerical reionization simulations. The SS is the cross-spectrum of the quadratic temperature brightness field with itself. We generate a set of seven simulations from $z = 30$ to $z = 5$, varying the halo mass threshold for hosting star-formation, the X-ray luminosity per star-formation rate, and the minimum X-ray energy escaping host galaxies. We find the SS is predominantly negative as a function of redshift, transitioning to positive towards the start of reionization, and peaking during the midpoint of reionization. We do not see a negative dip in the SS during reionization, likely due to the specifics of modelling ionization sources. We normalise the SS by the PS during reionization isolating the non-Gaussianities. We find a trough ($k\sim\,0.1\,\textrm{Mpc}^{-1}$) and peak ($k\sim\,0.4-1\,\textrm{Mpc}^{-1}$) in the normalised SS during the mid to late periods of reionization. These correlate to the ionization topology, and neutral islands in the IGM. We calculate the cosmic variance of the normalised SS, and find these features are detectable in the absence of foregrounds with the SKA_LOW., Comment: 19 pages, 14 figures