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NAM2012 - All Presentation Details

Record 311 of 756

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Interference Mitigation schemes for LOFAR dynamic spectra

Author: Dr. Ashish Asgekar

ASTRON, Netherlands Institute for Radio Astronomy

Co-Authors: R.A. Fallows (ASTRON, the Netherlands Institute for Radio Astronomy, & Institute of Mathematics and Physics, Aberystwyth University, Penglais Campus, Aberystwyth, SY23 3BZ, Wales, UK); S. ter Veen (Department of Astrophysics, University of Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands)

Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results

Presentation type: Talk      00:00  Poster Session B 


We present details of LOw Frequency ARray (LOFAR) dynamic spectrum data pipeline, focussing on the mitigation of Radio Frequency Interference (RFI) in the data sets. RFI can be categorised in two forms: persistent interference where entire frequency channels can be regarded as contaminated, and brief pulses where single spikes of RFI can exist at more random times and frequencies. The worst-affected frequency channels are identified using median filters. Most of the persistent interference can be identified in this way, allowing the median of each frequency channel to be interpolated in frequency across the 'bad’ channels. This creates an estimate of the telescope response across the pass-band, which is used to 'flatten’ the data. Two-dimensional (2-D) median filters are then employed to locate the remaining (more random) spikes of RFI. We also describe a method of "random substitution” to obtain 'clean' time-frequency data after RFI identification and mitigation. This may allow the calculation of bi-spectra and the development of novel ways to study interplanetary scintillation (IPS) and solar wind micro structure.

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