The Rapid ASKAP Continuum
Survey (RACS) completed a second survey of the entire sky early in
2021. This time it observed at an ASKAP mid-band frequency rather than
the lower-band used in the original RACS survey (we now refer to the
original survey as RACS-low and the mid-band survey as
RACS-mid). RACS-mid provides improved sensitivity and resolution and
also surveyed a significantly larger portion of the sky, covering all
declinations below +49 degrees. As a result of the rapid nature of the
survey, the 15-minute RACS-mid snapshot images are sometimes
inadvertently photo-bombed by a wandering planet as it passes through
the field being observed. While inspecting RACS-mid images for quality
checks, we found that over the two month period during which most of
the survey was observed all seven planets (excluding Earth) were
seen. Mercury and Venus appeared as a blur as they
are fast movers in the sky. Jupiter is particularly elongated because
of
its radiation
belts and they differ from the other planets in that they are also
visible, albeit weakly, in circular polarisation. The more distant
planets, Uranus and Neptune, are also more easily detected in RACS-mid
compared
to RACS-low
because planetary emission is generally brighter at higher
frequencies. In some cases we can also see background radio galaxies
in the image, e.g., close to Mars, Jupiter and Neptune. While these
planetary finds can be fun, just like photobombing during our own
holiday snaps, they can also be an annoyance and may require
re-observations (in case the planet was hiding a background object).
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