arXiv subjects

Alex Dunning

Publications and source records attributed to Alex Dunning.

4 recordsLinked to original sources

arXiv2026

Characterising and mitigating Bluetooth and WiFi radio frequency interference at the Parkes Observatory

We present a detailed characterisation of radio frequency interference (RFI) in the 2.4 GHz band around Murriyang, CSIRO's Parkes radio telescope. The dominant sources of interference are Wi-Fi and Bluetooth transmissions. We quantify how the intensity and directionality of this RFI vary with time of day and document its evolution over several years. Although most observers currently discard data within this band, our analysis shows that the interference is confined in both timeand frequency and can be effectively mitigated. Using 10 seconds of 16-bit voltage data recorded during observations of the Vela Pulsar (PSR J0835-4510), we demonstrate that the majority of the channelised data remain unaffected by RFI. We compare three RFI detection and mitigation algorithms and evaluate their relative performance. All methods perform effectively, and any could be implemented in real time to enable productive use of this observing band. A real time implementation would allow the scientific use of this 128 MHz observing band to increase, from almost 70% of the band being completely unusable all of the time, to over 90% of becoming accessible for science. Given its simplicity and efficiency, a basic power-threshold approach offers a relatively straightforward solution.

astro-ph.IM↗

arXiv2025

Precise Measurement of the Absolute Sky Brightness at 60-350 MHz

Accurate knowledge of the low-frequency radio sky is essential for modelling foregrounds in experiments targeting cosmic dawn and the epoch of reionization. Measurements below 1 GHz are also needed to understand the Galactic cosmic ray electron spectrum, constrain nanojansky radio source populations and dark matter models, investigate the origins of the diffuse radio background, and improve calibration of long-wavelength radio telescopes. Here we present a precision measurement of the radio sky brightness over 60-350 MHz using a new receiver architecture that self-calibrates its noise contribution and bandpass in situ while connected to an antenna. Our measurement used a log-periodic SKALA4.1 antenna on a 40 m diameter SKA-Low station ground mesh in the Southern Hemisphere to observe approximately half of the celestial sphere. We show that current all-sky maps and the 2016 Global Sky Model (GSM2016) require substantial corrections over this frequency range. GSM2016 must be scaled upward by a factor of 1.2 over 60-200 MHz, increasing to 1.5 at 350 MHz. A smaller offset correction of approximately 100 K is also required below 100 MHz. The revised scaling significantly increases previously inferred excess radio background, motivating review of faint source populations and dark-matter decay models. Sky models scaled to our measurements can set the absolute flux-density scale for SKA-Low and other low-frequency radio telescopes. They can also improve foreground characterisation for cosmic dawn and epoch-of-reionization experiments.

astro-ph.CO↗

arXiv2022

Simulating high-time resolution radio-telescope observations

We describe a new software package for simulating channelised, high-time resolution data streams from radio telescopes. The software simulates data from the telescope and observing system taking into account the observation strategy, receiver system and digitisation. The signatures of pulsars, fast radio bursts and flare stars are modelled, including frequency-dependent effects such as scattering and scintillation. We also simulate more generic signals using spline curves and images. Models of radio frequency interference include signals from satellites, terrestrial transmitters and impulsive, broadband signals. The simulated signals can also be injected into real data sets. Uses of this software include the production of machine learning training data sets, development and testing of new algorithms to search for anomalous patterns and to characterise processing pipelines.

astro-ph.IM↗

arXiv2018

Considerations for a Multi-beam Multi-purpose Survey with FAST

Having achieved 'first-light' right before the opening ceremony on September 25, 2016, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is being busily commissioned. Its innovative design requires ~1000 points to be measured and driven instead of just the two axes of motion, e.g. Azimuth and Elevation for most of the conventional antennae, to realize pointing and tracking. We have devised a survey plan to utilized the full sensitivity of FAST, while minimizing the complexities in operation the system. The 19-beam L band focal plan array will be rotated to specific angles and taking continuous data streams while the surface shape and the focal cabin stay fixed. Such a survey will cover the northern sky in about 220 full days. Our aim is to obtain data for pulsar search, HI (neutral hydrogen) galaxies, HI imaging, and radio transients, simultaneously, through multiple backends. These data sets could be a significant contribution to all related fields in radio astronomy and remain relevant for decades.

astro-ph.IM↗