Timing calibration and spectral cleaning of LOFAR time series data

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Timing calibration and spectral cleaning of LOFAR time series data

Corstanje, A. (author): Radboud University Nijmegen, The Netherlands

Buitink, S. (author): Vrije Universiteit Brussel, Belgium

Enriquez, J. E. (author): Radboud University Nijmegen, The Netherlands

Falcke, H. (author): Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands ; Netherlands Institute for Radio Astronomy, The Netherlands ; Max Planck Institute for Radio Astronomy, Germany

Hörandel, J. R. (author): Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands

Krause, M. (author): Deutsches Elektronen-Synchrotron, Germany

Nelles, A. (author): Radboud University Nijmegen, The Netherlands ; University of California Irvine, USA

Rachen, J. P. (author): Radboud University Nijmegen, The Netherlands

Schellart, P. (author): Radboud University Nijmegen, The Netherlands

Scholten, O. (author): University Groningen, The Netherlands ; Vrije Universiteit Brussel, Belgium

ter Veen, S. (author): Radboud University Nijmegen, The Netherlands

Thoudam, Satyendra (author): Radboud University Nijmegen, The Netherlands

Trinh, T. N. G. (author): University Groningen, The Netherlands

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(creator_code:org_t)

2016-05-04
2016
English.
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 590

Related links:: https://doi.org/10.1...; show more...; http://arxiv.org/abs...; https://www.aanda.or...; https://urn.kb.se/re...; https://doi.org/10.1...; show less...

Journal article (peer-reviewed)

Abstract Subject headings

We describe a method for spectral cleaning and timing calibration of short voltage time series data from individual radio interferometer receivers. It makes use of the phase differences in Fast Fourier Transform (FFT) spectra across antenna pairs. For strong, localized terrestrial sources these are stable over time, while being approximately uniform-random for a sum over many sources or for noise. Using only milliseconds-long datasets, the method finds the strongest interfering transmitters, a first-order solution for relative timing calibrations, and faulty data channels. No knowledge of gain response or quiescent noise levels of the receivers is required. With relatively small data volumes, this approach is suitable for use in an online system monitoring setup for interferometric arrays. We have applied the method to our cosmic-ray data collection, a collection of measurements of short pulses from extensive air showers, recorded by the LOFAR radio telescope. Per air shower, we have collected 2 ms of raw time series data for each receiver. The spectral cleaning has a calculated optimal sensitivity corresponding to a power signal-to-noise ratio of 0.08 (or -11 dB) in a spectral window of 25 kHz, for 2 ms of data in 48 antennas. This is well sufficient for our application. Timing calibration across individual antenna pairs has been performed at 0.4 ns precision; for calibration of signal clocks across stations of 48 antennas the precision is 0.1 ns. Monitoring differences in timing calibration per antenna pair over the course of the period 2011 to 2015 shows a precision of 0.08 ns, which is useful for monitoring and correcting drifts in signal path synchronizations. A cross-check method for timing calibration is presented, using a pulse transmitter carried by a drone flying over the array. Timing precision is similar, 0.3 ns.

Subject headings

NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Keyword

Astrophysics - Instrumentation and Methods for Astrophysics
Astroparticle Physics
Astropartikelfysik

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By the author/editor: Corstanje, A.; Buitink, S.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Krause, M.; show more...; Nelles, A.; Rachen, J. P.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, Satyend ...; Trinh, T. N. G.; show less...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

Articles in the publication: Astronomy and As ...

By the university: Linnaeus University

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