Water Vapour Radiometers for the Australia Telescope Compact Array

TL;DR

This paper presents Water Vapour Radiometers for the Australia Telescope Compact Array, which measure atmospheric water vapour fluctuations to correct phase delays, enhancing telescope efficiency and resolution at high frequencies.

Contribution

Development and implementation of WVRs for ATCA to improve phase correction and imaging quality in radio astronomy.

Findings

WVRs successfully measure atmospheric water vapour fluctuations.

Phase correction improves telescope efficiency and enables longer baselines.

Enhanced spatial resolution at higher frequencies.

Abstract

We have developed Water Vapour Radiometers (WVRs) for the Australia Telescope Compact Array (ATCA) that are capable of determining signal path length fluctuations by virtue of measuring small temperature fluctuations in the atmosphere using the 22.2 GHz water vapour line for each of the six antennae. By measuring the line of sight variations of the water vapour, the induced path excess and thus the phase delay can be estimated and corrections can then be applied during data reduction. This reduces decorrelation of the source signal. We demonstrate how this recovers the telescope's efficiency as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution. A description of the WVR hardware design, their calibration and water vapour retrieval mechanism is given.