Sky Noise Limited Snapshot Imaging in the Presence of RFI with LOFAR’s Initial Test Station

  • Stefan J. Wijnholds
  • Jaap D. Bregman
  • Albert-Jan Boonstra
Chapter

Abstract

The initial test station (ITS) is the first full scale prototype of a low frequency array (LOFAR) station. It operates in the 10–40 MHz range and consists of 60 sky noise limited dipoles arranged in a five-armed spiral structure offering an instantaneous synthesized aperture of almost 200 m diameter. We will present all sky snapshot images demonstrating sky-noise limited imaging capability in the presence of a strong RFI source that exceeds the all sky power by 27 dB. This result is obtained with a two stage self-calibration procedure. First, the RFI source near the horizon is used as calibrator and then subtracted, after which Cas A shows up at a level that is a factor 2000 lower and then dominates the picture with its side lobes. A second self calibration on Cas A then reveals the same extended galactic emission as found in a RFI free adjacent spectral channel. This demonstrates that a single 10 kHz channel of a 6.7 s snapshot of a single LOFAR station already provides a dynamic range of over 104.

Keywords

CLEAN LOFAR peeling phased array RFI RFI mitigation snapshot imaging 

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References

  1. Boonstra, A. J. and van der Tol, S.: accepted for publication, Spatial filtering of interfering signals at the initial LOFAR phased array test station: Radio Science, Special section on Mitigation in Radio Frequency Interference (RFI) in Radio Astronomy.Google Scholar
  2. Noordam, J. E.: 2004, LOFAR Calibration Challenges, SPIE conference on astronomical telescopes and instrumentation, Glasgow (UK), June 21–25, 2004.Google Scholar
  3. van der Veen, A. J., Leshem, A., and Boonstra, A. J.: 2004, Signal Processing for Radio Astronomical Arrays, SAM workshop, Barcelona (Spain), July 18–21, 2004.Google Scholar

Copyright information

© Springer 2005

Authors and Affiliations

  • Stefan J. Wijnholds
    • 1
  • Jaap D. Bregman
    • 1
  • Albert-Jan Boonstra
    • 1
  1. 1.ASTRONDwingelooThe Netherlands

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