Roger J. Cappallo

Real-Time Calibration of the Murchison Widefield Array

The interferometric technique known as peeling addresses many of the challenges faced when observing with low-frequency radio arrays, and is a promising tool for the associated calibration systems. We investigate a real-time peeling implementation for next-generation radio interferometers such as the Murchison widefield array (MWA). The MWA is being built in Australia and will observe the radio sky between 80 and 300 MHz. The data rate produced by the correlator is just over 19 GB/s (a few peta-bytes/day). It is impractical to store data generated at this rate, and software is currently being developed to calibrate and form images in real time. The software will run on-site on a high-throughput real-time computing cluster at several tera-flops, and a complete cycle of calibration and imaging will be completed every 8 s. Various properties of the implementation are investigated using simulated data. The algorithm is seen to work in the presence of strong galactic emission and with various ionospheric conditions. It is also shown to scale well as the number of antennas increases, which is essential for many upcoming instruments. Lessons from MWA pipeline development and processing of simulated data may be applied to future low-frequency fixed dipole arrays.

Transient Science with the MWA

The Murchison Widefield Array is a radiotelescope, currently under construction in the outback of Western Australia, that consists of an array of 512 dipole tiles. The MWA will cover the frequency band from 80 to 300 MHz, with an instantaneous processed bandwidth of 31 MHz, and a ~30° FWHM primary beam. Its wide field of view, excellent RFI environment, and novel software systems will allow unprecedented capabilities for discovering and observing transient radio sources. This paper describes the relevant hardware and software features of the instrument, and shows what they imply for sensitivity to various transient phenomena.