In situ measurement of MWA primary beam variation using ORBCOMM
We provide the first in situ measurements of antenna element (tile) beam shapes of the Murchison Widefield Array (MWA), a low radio-frequency interferometer and an SKA precursor. Most current MWA processing pipelines use an assumed beam shape, errors in which can cause absolute and relative flux den...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Journal Article |
| Published: |
Cambridge University Press
2018
|
| Online Access: | http://hdl.handle.net/20.500.11937/74853 |
| _version_ | 1848763390574460928 |
|---|---|
| author | Line, J. McKinley, B. Rasti, J. Bhardwaj, M. Wayth, Randall Webster, R. Ung, D. Emrich, David Horsley, L. Beardsley, A. Crosse, B. Franzen, T. Gaensler, B. Johnston-Hollitt, M. Kaplan, D. Kenney, D. Morales, M. Pallot, D. Steele, K. Tingay, S. Trott, Cathryn Walker, M. Williams, Andrew Wu, C. |
| author_facet | Line, J. McKinley, B. Rasti, J. Bhardwaj, M. Wayth, Randall Webster, R. Ung, D. Emrich, David Horsley, L. Beardsley, A. Crosse, B. Franzen, T. Gaensler, B. Johnston-Hollitt, M. Kaplan, D. Kenney, D. Morales, M. Pallot, D. Steele, K. Tingay, S. Trott, Cathryn Walker, M. Williams, Andrew Wu, C. |
| author_sort | Line, J. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We provide the first in situ measurements of antenna element (tile) beam shapes of the Murchison Widefield Array (MWA), a low radio-frequency interferometer and an SKA precursor. Most current MWA processing pipelines use an assumed beam shape, errors in which can cause absolute and relative flux density errors, as well as polarisation 'leakage'. This makes understanding the primary beam of paramount importance, especially for sensitive experiments such as a measurement of the 21 cm line from the epoch of reionisation (EoR). The calibration requirements for measuring the EoR 21 cm line are so extreme that tile to tile beam variations may affect our ability to make a detection. Measuring the primary beam shape from visibilities alone is challenging, as multiple instrumental, atmospheric, and astrophysical factors contribute to uncertainties in the data. Building on the methods of Neben et al. (2015), we tap directly into the receiving elements of the MWA before any digitisation or correlation of the signal. Using ORBCOMM satellite passes we are able to produce all-sky maps for 4 separate tiles in the XX polarisation. We find good agreement with the cutting-edge 'fully' embedded element (FEE) model of Sokolowski et al. (2017), and observe that the MWA beamformers consistently recreate beam shapes to within ~1dB in the reliable areas of our beam maps. We also clearly observe the effects of a missing dipole from a tile in one of our beam maps, and show that the FEE model is able to reproduce this modified beam shape. We end by motivating and outlining additional onsite experiments to further constrain the primary beam behaviour. |
| first_indexed | 2025-11-14T11:02:42Z |
| format | Journal Article |
| id | curtin-20.500.11937-74853 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T11:02:42Z |
| publishDate | 2018 |
| publisher | Cambridge University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-748532019-08-07T06:41:35Z In situ measurement of MWA primary beam variation using ORBCOMM Line, J. McKinley, B. Rasti, J. Bhardwaj, M. Wayth, Randall Webster, R. Ung, D. Emrich, David Horsley, L. Beardsley, A. Crosse, B. Franzen, T. Gaensler, B. Johnston-Hollitt, M. Kaplan, D. Kenney, D. Morales, M. Pallot, D. Steele, K. Tingay, S. Trott, Cathryn Walker, M. Williams, Andrew Wu, C. We provide the first in situ measurements of antenna element (tile) beam shapes of the Murchison Widefield Array (MWA), a low radio-frequency interferometer and an SKA precursor. Most current MWA processing pipelines use an assumed beam shape, errors in which can cause absolute and relative flux density errors, as well as polarisation 'leakage'. This makes understanding the primary beam of paramount importance, especially for sensitive experiments such as a measurement of the 21 cm line from the epoch of reionisation (EoR). The calibration requirements for measuring the EoR 21 cm line are so extreme that tile to tile beam variations may affect our ability to make a detection. Measuring the primary beam shape from visibilities alone is challenging, as multiple instrumental, atmospheric, and astrophysical factors contribute to uncertainties in the data. Building on the methods of Neben et al. (2015), we tap directly into the receiving elements of the MWA before any digitisation or correlation of the signal. Using ORBCOMM satellite passes we are able to produce all-sky maps for 4 separate tiles in the XX polarisation. We find good agreement with the cutting-edge 'fully' embedded element (FEE) model of Sokolowski et al. (2017), and observe that the MWA beamformers consistently recreate beam shapes to within ~1dB in the reliable areas of our beam maps. We also clearly observe the effects of a missing dipole from a tile in one of our beam maps, and show that the FEE model is able to reproduce this modified beam shape. We end by motivating and outlining additional onsite experiments to further constrain the primary beam behaviour. 2018 Journal Article http://hdl.handle.net/20.500.11937/74853 10.1017/pasa.2018.30 Cambridge University Press restricted |
| spellingShingle | Line, J. McKinley, B. Rasti, J. Bhardwaj, M. Wayth, Randall Webster, R. Ung, D. Emrich, David Horsley, L. Beardsley, A. Crosse, B. Franzen, T. Gaensler, B. Johnston-Hollitt, M. Kaplan, D. Kenney, D. Morales, M. Pallot, D. Steele, K. Tingay, S. Trott, Cathryn Walker, M. Williams, Andrew Wu, C. In situ measurement of MWA primary beam variation using ORBCOMM |
| title | In situ measurement of MWA primary beam variation using ORBCOMM |
| title_full | In situ measurement of MWA primary beam variation using ORBCOMM |
| title_fullStr | In situ measurement of MWA primary beam variation using ORBCOMM |
| title_full_unstemmed | In situ measurement of MWA primary beam variation using ORBCOMM |
| title_short | In situ measurement of MWA primary beam variation using ORBCOMM |
| title_sort | in situ measurement of mwa primary beam variation using orbcomm |
| url | http://hdl.handle.net/20.500.11937/74853 |