Low Frequency Observations of the Moon with the Murchison Widefield
  Array
  A new generation of low frequency radio telescopes is seeking to observe the
redshifted 21 cm signal from the Epoch of Reionization (EoR), requiring
innovative methods of calibration and imaging to overcome the difficulties of
widefield low frequency radio interferometry. Precise calibration will be
required to separate the small expected EoR signal from the strong foreground
emission at the frequencies of interest between 80 and 300 MHz. The Moon may be
useful as a calibration source for detection of the EoR signature, as it should
have a smooth and predictable thermal spectrum across the frequency band of
interest. Initial observations of the Moon with the Murchison Widefield Array
32 tile prototype show that the Moon does exhibit a similar trend to that
expected for a cool thermally emitting body in the observed frequency range,
but that the spectrum is corrupted by reflected radio emission from Earth. In
particular, there is an abrupt increase in the observed flux density of the
Moon within the internationally recognised Frequency Modulated (FM) radio band.
The observations have implications for future low frequency surveys and EoR
detection experiments that will need to take this reflected emission from the
Moon into account. The results also allow us to estimate the equivalent
isotropic power emitted by the Earth in the FM band and to determine how bright
the Earth might appear at metre wavelengths to an observer beyond our own solar
system.
