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Reduced ambiguity calibration for LOFAR

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Abstract

Interferometric calibration always yields non unique solutions. It is therefore essential to remove these ambiguities before the solutions could be used in any further modeling of the sky, the instrument or propagation effects such as the ionosphere. We present a method for LOFAR calibration which does not yield a unitary ambiguity, especially under ionospheric distortions. We also present exact ambiguities we get in our solutions, in closed form. Casting this as an optimization problem, we also present conditions for this approach to work. The proposed method enables us to use the solutions obtained via calibration for further modeling of instrumental and propagation effects. We provide extensive simulation results on the performance of our method. Moreover, we also give cases where due to degeneracy, this method fails to perform as expected and in such cases, we suggest exploiting diversity in time, space and frequency.

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Acknowledgements

We thank Ger de Bruyn and Wim Brouw for initial comments and suggestions. We also thank the anonymous reviewers for the careful review and helpful comments that enabled us to enhance this paper.

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  1. ASTRON, Dwingeloo, The Netherlands

    Sarod Yatawatta

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  1. Sarod Yatawatta
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Correspondence to Sarod Yatawatta.

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Yatawatta, S. Reduced ambiguity calibration for LOFAR. Exp Astron 34, 89–103 (2012). https://doi.org/10.1007/s10686-012-9300-7

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  • DOI: https://doi.org/10.1007/s10686-012-9300-7

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