Measuring the global 21-cm signal with the MWA-I: improved measurements
  of the Galactic synchrotron background using lunar occultation
  We present early results from a project to measure the sky-averaged (global),
redshifted $21\,$cm signal from the Epoch of Reionisation (EoR), using the
Murchison Widefield Array (MWA) telescope. Because interferometers are not
sensitive to a spatially-invariant global average, they cannot be used to
detect this signal using standard techniques. However, lunar occultation of the
radio sky imprints a spatial structure on the global signal, allowing us to
measure the average brightness temperature of the patch of sky immediately
surrounding the Moon. In this paper we present one night of Moon observations
with the MWA between 72 - 230 MHz and verify our techniques to extract the
background sky temperature from measurements of the Moon's flux density. We
improve upon previous work using the lunar occultation technique by using a
more sophisticated model for reflected `earthshine' and by employing image
differencing to remove imaging artefacts. We leave the Moon's (constant) radio
brightness temperature as a free parameter in our fit to the data and as a
result, measure $T_{\rm{moon}} = 180 \pm 12 $ K and a Galactic synchrotron
spectral index of $-2.64\pm0.14$, at the position of the Moon. Finally, we
evaluate the prospects of the lunar occultation technique for a global EoR
detection and map out a way forward for future work with the MWA.
