coherent noise in the receiver boxes, which affects some sets of adjacent modules, and other inefficiencies in the system performance that we are still characterising, such as systematic errors in the phase/delay solutions across the interferometer (Bailes et al. in submitted).

At present (October 2016), we estimate $\upepsilon \approx 0.14$, based on observations of strong calibrators of known flux densities and a number of high DM pulsars with relatively stable flux densities. This implies an effective $T_\mathrm{sys}$ of $400 \pm 100$ K. This is significantly higher than the system temperature seen on the best performing modules, which can be as low as 100 K. We note that $\upepsilon$ can vary from day to day as modules are either serviced in the field or have electronics maintenance in the workshops, and typically lie in the range $0.15 < \upepsilon <
0.20$. Occasionally, if only one arm is operational, we have the option to continue surveys at half sensitivity (i.e. $0.07 < \upepsilon < 0.10$). The telescope can access the Southern sky for $\delta < +18^{\circ}$, and for most parts of the sky we tend to observe reasonably close to the meridian, in order to maximise sensitivity. The sensitivity is reduced by 