Primary beam sensitivity patterns determined by holography. The central panel shows, on a logarithmic scale, the sensitivity pattern for beam-0 at 930 MHz, which in the RACS footprint is offset 0.525 • from the field centre in both cardinal directions. This display clearly shows the corner regions of the field not sampled during the holography measurements. The dashed square marks the boundary of the image made for beam-0. The top panel shows the variation of sensitivity on a linear scale, horizontally through the beam centre. The bottom panel shows all beams as contours at their half-power level. An estimate of the sensitivity of the 36-beam mosaic is indicated by the density of shading, with the outer contour drawn at the 50 percent level. The white cross in bottom and central panels marks the intended centre of beam-0.

Contexts in source publication

Context 1

... is the largest image size practical using the Galaxy computer cluster in its current configuration. Each beam image has a 4.2 • extent, which covers the main lobe of the primary beam at the high-frequency end of the band, and reaches the 4 percent sensitivity level at the low-frequency end (see Figure 5). The weighting of visibility measurements is achieved by preconditioning (Rau, 2010), an approach designed to minimise data access load on the software. ...

Context 2

... was used to span gaps in the spectrum caused by radio-frequency interference. Figure 5 shows the mean pattern for beam-0 over 26 of the 32 measured antennas (the missing four were the reference antenna and three others that were unavailable during the holography observations) and the measured shape at half-power of all beams in the footprint. All of the 26 antennas used for the array-wide mean had power patterns differing from the mean by less than 4 per cent. ...