LEAP: An innovative direction-dependent ionospheric calibration scheme for low-frequency arrays

María J. Rioja, Richard Dodson, Thomas M.O. Franzen

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The ambitious scientific goals of the SKA require a matching capability for calibration of atmospheric propagation errors, which contaminate the observed signals. We demonstrate a scheme for correcting the direction-dependent ionospheric and instrumental phase effects at the low frequencies and with the wide fields of view planned for SKA-Low. It leverages bandwidth smearing, to filter out signals from off-axis directions, allowing the measurement of the direction-dependent antenna-based gains in the visibility domain; by doing this towards multiple directions it is possible to calibrate across wide fields of view. This strategy removes the need for a global sky model, therefore all directions are independent.We useMWA results at 88 and 154 MHz under various weather conditions to characterize the performance and applicability of the technique.We conclude that this method is suitable to measure and correct for temporal fluctuations and direction-dependent spatial ionospheric phase distortions on a wide range of scales: both larger and smaller than the array size. The latter are the most intractable and pose a major challenge for future instruments. Moreover, this scheme is an embarrassingly parallel process, as multiple directions can be processed independently and simultaneously. This is an important consideration for the SKA, where the current planned architecture is one of compute-islands with limited interconnects. Current implementation of the algorithm and ongoing developments are discussed.

Original languageEnglish
Pages (from-to)2337-2349
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume478
Issue number2
DOIs
Publication statusPublished - 1 Aug 2018

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field of view
ionospherics
low frequencies
calibration
visibility
antenna
filter
weather
sky
antennas
bandwidth
filters
propagation
weather condition
effect
method
need

Cite this

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abstract = "The ambitious scientific goals of the SKA require a matching capability for calibration of atmospheric propagation errors, which contaminate the observed signals. We demonstrate a scheme for correcting the direction-dependent ionospheric and instrumental phase effects at the low frequencies and with the wide fields of view planned for SKA-Low. It leverages bandwidth smearing, to filter out signals from off-axis directions, allowing the measurement of the direction-dependent antenna-based gains in the visibility domain; by doing this towards multiple directions it is possible to calibrate across wide fields of view. This strategy removes the need for a global sky model, therefore all directions are independent.We useMWA results at 88 and 154 MHz under various weather conditions to characterize the performance and applicability of the technique.We conclude that this method is suitable to measure and correct for temporal fluctuations and direction-dependent spatial ionospheric phase distortions on a wide range of scales: both larger and smaller than the array size. The latter are the most intractable and pose a major challenge for future instruments. Moreover, this scheme is an embarrassingly parallel process, as multiple directions can be processed independently and simultaneously. This is an important consideration for the SKA, where the current planned architecture is one of compute-islands with limited interconnects. Current implementation of the algorithm and ongoing developments are discussed.",
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LEAP : An innovative direction-dependent ionospheric calibration scheme for low-frequency arrays. / Rioja, María J.; Dodson, Richard; Franzen, Thomas M.O.

In: Monthly Notices of the Royal Astronomical Society, Vol. 478, No. 2, 01.08.2018, p. 2337-2349.

Research output: Contribution to journalArticle

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