MeerKAT Holography Measurements in the UHF, L, and S bands

TL;DR

This paper presents comprehensive holography measurements of the MeerKAT telescope across UHF, L, and S bands, analyzing electromagnetic performance, beam characteristics, and reflector errors to improve understanding of its observational capabilities.

Contribution

It provides the first detailed comparison of MeerKAT's holographic measurements across multiple bands, highlighting differences in electromagnetic performance and pointing errors.

Findings

Similar electromagnetic performance in UHF and L bands due to shared design

Distinct performance characteristics and higher-order mode activation in S band

Elevation and temperature effects influence collimation and surface errors

Abstract

Radio holographic measurements using the MeerKAT telescope are presented for each of its supported observing bands, namely UHF (544--1087 MHz), L (856--1711 MHz) and S (1750--3499 MHz). Because the UHF-band receiver design is a scaled version of that of the L band, the electromagnetic performance in these two bands are expectedly similar to one another. Despite also being linearly polarized, S-band receivers have an entirely different design and distinct performance characteristics from the lower two bands. As introduced in previous work for the L band, evidence of higher-order waveguide mode activation also appears in S-band measurements but there are differences in its manifestation. Frequency-dependent pointing (beam squint), beam width, beam ellipticity, errorbeam, instrumental polarization and cross-polarization power measurements are illustrated for each of MeerKAT's observational bands in a side-by-side style to facilitate the comparison of features. The derivation of collimation errors and main reflector surface errors from measurements made at these relatively low observation frequencies is also discussed. Results include elevation and ambient temperature effects on collimation, as well as the signatures of collimation degrading over time. The accompanying data release includes a snapshot of full Jones matrix primary beam patterns for all bands and antennas, with corresponding derived metrics.