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We present a millimetre-wave site characterisation for the AustraliaTelescope Compact Array (ATCA) based on nearly 9 years of data from a seeingmonitor operating at this facility. The seeing monitor, which measures thephase fluctuations in the signal from a geosynchronous satellite over a 230\,mbaseline caused by water vapour fluctuations along their sight lines, providesan almost gapless record since 2005, with high time resolution. We determinethe root mean square (rms) of the path length variations as a function of timeof day and season. Under the assumption of the "frozen screen" hypothesis, wealso determine the Kolomogorov exponent, $\alpha$, for the turbulence and thephase screen speed. From these, we determine the millimetre-wave seeing at$\lambda = 3.3$\,mm. Based on the magnitude of the rms path length variations,we estimate the expected fraction of the available observing time wheninterferometry could be successfully conducted using the ATCA, as a function ofobserving frequency and antenna baseline, for the time of day and the season.We also estimate the corresponding observing time fractions when using thewater vapour radiometers (WVRs) installed on the ATCA in order to correct forthe phase fluctuations occurring during the measurement of an astronomicalsource.

Millimetre-wave Site Characteristics at the Australia Telescope Compact Array