EDP Sciences
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Erratum
This article is an erratum for: [this article]

Issue
A&A
Volume 581, September 2015
Article Number C4
Number of page(s) 2
Section Astronomical instrumentation
DOI https://doi.org/10.1051/0004-6361/201220728e
Published online 17 September 2015

thumbnail Fig. 2

GIMs representing the VTEC across the globe for April 11th, 2011 (the date of the first LOFAR observing campaign, see Sect. 5) obtained courtesy of CODE. The maps range from minimum (blue) to maximum (red) VTEC values of 0.0−87.2 TECU (1 TECU = 1016 electrons/m2). The triangles indicate the location of the LOFAR core stations in the Netherlands, the squares mark the SKA core sites in South Africa and Western Australia, and the circles indicate the site of the GMRT.

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This erratum corrects Figs. 2 and 3 of our original paper (Sotomayor-Beltran et al. 2013). Due to a simple error in plotting the input data, these maps of ionospheric total electron content (TEC) were inverted north-south and improperly stretched to match the underlying cartographic projection. The properly mapped figures are presented here (see also the Appendix of Arora et al. 2015). The ionospheric prediction code, ionFR, and other figures presented in the paper were not affected by this

thumbnail Fig. 3

The VTEC across Europe for March 23rd, 2012 (the date of the third LOFAR campaign, see Sect. 5) at 00:00 UT, obtained courtesy of ROB. The square indicates the LOFAR core stations and the triangles represent the locations of the international stations.

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inversion error, which was purely a plotting error applying to Figs. 2 and 3.

This mapping error led to the incorrect conclusion that the Equatorial Ionization Anomaly (EIA) can sometimes pass directly over the planned sites of the Square Kilometre Array (SKA). Though ionospheric calibration is a challenging problem, it is a challenge that is being met (e.g., Arora et al. 2015). Unfortunately, the incorrect assertion that the EIA passes over the chosen sites for the SKA overstated the severity of the problem for these locations, which have been meticulously chosen and proven to be excellent sites for low-frequency radio astronomy.

All other conclusions in the paper remain unaffected.

Acknowledgments

We sincerely thank David Herne, Mervyn Lynch, and John Kennewell for discovering this error and bringing it to our attention.

References


© ESO, 2015

All Figures

thumbnail Fig. 2

GIMs representing the VTEC across the globe for April 11th, 2011 (the date of the first LOFAR observing campaign, see Sect. 5) obtained courtesy of CODE. The maps range from minimum (blue) to maximum (red) VTEC values of 0.0−87.2 TECU (1 TECU = 1016 electrons/m2). The triangles indicate the location of the LOFAR core stations in the Netherlands, the squares mark the SKA core sites in South Africa and Western Australia, and the circles indicate the site of the GMRT.

Open with DEXTER
In the text
thumbnail Fig. 3

The VTEC across Europe for March 23rd, 2012 (the date of the third LOFAR campaign, see Sect. 5) at 00:00 UT, obtained courtesy of ROB. The square indicates the LOFAR core stations and the triangles represent the locations of the international stations.

Open with DEXTER
In the text

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