MeerKAT Primary Beam Measurements in the L Band

Full-polarization primary beam patterns of MeerKAT antennas have been measured in
L-band (856 to 1711 MHz) by means of radio holography using celestial targets. This paper
presents the observed frequency dependent properties of these beams, and guides users of this
64 antenna radio telescope that are concerned by its direction dependent polarization effects. In
this work the effects on the primary beams due to modeling simplifications, bandwidth
averaging, gravitational loading and ambient temperature are quantified within the half power
region of the beam. A perspective is provided on the level of significance of typical use case
effects. It is shown that antenna pointing is a leading cause of inaccuracy for telescope users in
the presumed beam shape, introducing errors exceeding 1% in power near the half power point
of beams, owing to a telescope pointing accuracy of sigma is approximately 0.6 arcminutes.
Disregarding these pointing errors, variability in the Stokes I beam shape relative to the array
average is most commonly around 0.3% in power; however, the impact above 1500 MHz is on
average triple that of the lower half of the band. This happens because the proportion of higher
order waveguide modes that are activated and propagate is sensitive to small manufacturing
differences in the orthomode transducer for each receiver. Primary beam correction verification
test results for an off-axis spectral index measurement experiment are included.