Measuring phased-array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137MHz ORBCOMM satellites
MetadataShow full item record
Detection of the fluctuations in a 21 cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased-array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137 MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the in situ beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering) and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second-reference dipole. We achieve beam measurements over 30 dB dynamic range in beam sensitivity over a large field of view (65% of the visible sky), far wider and deeper than drift scans through astronomical sources allow. We verify an analytic model of the MWA tile at this frequency within a few percent statistical scatter within the full width at half maximum. Toward the edges of the main lobe and in the sidelobes, we measure tens of percent systematic deviations. We compare these errors with those expected from known beamforming errors.
Copyright © 2015 American Geophysical Union. Reproduced by permission.
Showing items related by title, author, creator and subject.
Colegate, Timothy Maarten (2012)The Square Kilometre Array (SKA) radio telescope is being designed as a premier scientific instrument of the 21st century, using novel technologies to maximise its scientific capability. The SKA has an aggressive project ...
Beam-forming errors in Murchison Widefield array phased array antennas and their effects on epoch of reionization scienceNeben, A.; Hewitt, J.; Bradley, R.; Dillon, J.; Bernardi, G.; Bowman, J.; Briggs, F.; Cappallo, R.; Corey, B.; Deshpande, A.; Goeke, R.; Greenhill, L.; Hazelton, B.; Johnston-Hollitt, M.; Kaplan, D.; Lonsdale, C.; McWhirter, S.; Mitchell, D.; Morales, M.; Morgan, E.; Oberoi, D.; Ord, S.; Prabu, T.; Shankar, N.; Srivani, K.; Subrahmanyan, R.; Tingay, Steven; Wayth, Randall; Webster, R.; Williams, A.; Williams, C. (2016)Accurate antenna beam models are critical for radio observations aiming to isolate the redshifted 21 cm spectral line emission from the Dark Ages and the Epoch of Reionization (EOR) and unlock the scientific potential of ...
Sutinjo, Adrian; Hall, Peter (2014)We present antenna rotation error tolerance analysis for a polarimeter consisting of dual-linearly polarized dipole-like elements. Treating the elements as a phased array and expressing the measurement basis as circularly ...