GBD-DART-I : Pulsars and transient source observation between 130 MHz and 350 MHz at Gauribidanur

TL;DR

GBD-DART presents a 64-element diamond-configured LPDA array at Gauribidanur designed for 130–350 MHz pulsar and solar transient observations. The work details an end-to-end system with custom analog front-end, RF over fiber transport, and a digital backend, achieving 16 MHz instantaneous bandwidth per polarization and remote operation. Demonstrated results include satellite/Sun transits, daily drift measurements, solar flare detection, and detections of multiple bright pulsars, with data products processed through standard pulsar pipelines and validated against catalogs. The setup serves as a low-cost, educational platform for hands-on radio astronomy, while outlining clear paths to enhanced sensitivity, broader bandwidth, additional tiles, and advanced beamforming for transient studies.

Abstract

Gauribidanur Diamond Array Radio Telescope (GBD-DART) is a new small LPDA antenna array consisting of 64 short dipoles and associated receivers that has been custom developed and deployed at the Gauribidanur observatory (13.604 N, 77.427 E) to study bright Pulsars and Solar transients in the frequency range of 130-350 MHz. The LPDAs are arranged in a checkerboard layout, with opposite pairs combined to enable dual-polarised operation. A diamond-shaped (tilted square) array configuration was chosen to achieve high sidelobe suppression in the East-West and North-South directions. The tile measures 5.9 meters by 5.9 meters, with diagonals along both the North-South and East-West directions, each measuring about 8.4 meters. The LPDA array with one diamond-shaped tile has been fully commissioned and is operating in transit-observing mode, successfully detecting strong pulsars and solar flares over the last seven months. The present digital backend restricts the instantaneous bandwidth for observations to 16 MHz. The array operations are streamlined to facilitate remote operations. Apart from investigating Pulsar and Solar phenomena at low radio frequencies in selected sources, this work aims to provide a training platform for radio astronomy through simple-to-construct, low-cost radio telescopes. In this paper, we present details of the array, including antenna and array response studies, brief descriptions of front-end and backend instrumentation, and illustrative results from observations of both pulsars and solar flares. It will also provide brief details of future upgrade plans, particularly for the tiles and digital backend, to facilitate the observation of additional sources.

Figures (12)

• Figure 1: Typical (a) spectrum and (b) spectrogram observed in the RFI measurements at the Gauribidanur observatory from 2022.
• Figure 2: (a) Single LPDA Antenna. The second boom with complement dipoles is joined along the side to form the 11-element LPDA. The responses obtained at 150, 200, 250, 300 and 350 MHz are overlaid for E-plane in (b) and H-plane in (c). (d) Pyramid antenna element (e) Pyramid antenna element E-plane gain (f) Pyramid antenna element H-plane gain . The simulations carried out using the CST® software package
• Figure 3: Simulated S11 (blue dashed line) of the LPDA from CST software is compared with measured S11 (solid red line) by N9916B microwave analyser.
• Figure 4: Diamond antenna array deployment in the field. White boxes seen house first stage analog electronic components. A metal mesh with gap of 1/16 th wavelength of the highest operating frequency isolates the array form ground.
• Figure 5: Far-field orthographic responses of the diamond array with only single, two, eight and 32 LPDAs at 150, 250 and 350 MHz