EDP Sciences
Free access
Volume 471, Number 3, September I 2007
Page(s) 1099 - 1104
Section Astronomical instrumentation
DOI http://dx.doi.org/10.1051/0004-6361:20077204

A&A 471, 1099-1104 (2007)
DOI: 10.1051/0004-6361:20077204

VLBI observations of Jupiter with the initial test station of LOFAR and the Nançay decametric array

A. Nigl1, P. Zarka2, J. Kuijpers1, H. Falcke3, L. Bähren3, and L. Denis2

1  Department of Astrophysics (IMAPP), Radboud University Nijmegen, 6535 ED Nijmegen, The Netherlands
    e-mail: anigl@astro.ru.nl
2  LESIA, CNRS/Observatoire de Paris, 92195 Meudon, France
3  ASTRON, 7990 AA Dwingeloo, The Netherlands

(Received 31 January 2007 / Accepted 31 May 2007)

Aims.To demonstrate and test the capability of the next generation of low-frequency radio telescopes to perform high resolution observations across intra-continental baselines. Jupiter's strong burst emission is used to perform broadband full signal cross-correlations on time intervals of up to hundreds of milliseconds.
Methods.Broadband VLBI observations at about 20 MHz on a baseline of ~50 000 wavelengths were performed to achieve arcsecond angular resolution. LOFAR's Initial Test Station (LOFAR/ITS, The Netherlands) and the Nançay Decametric Array (NDA, France) digitize the measured electric field with 12 bit and 14 bit in a 40 MHz baseband. The fine structure in Jupiter's signal was used for data synchronization prior to correlation on the time-series data.
Results.Strong emission from Jupiter was detected during snapshots of a few seconds and detailed features down to microsecond time-scales were identified in dynamic spectra. Correlations of Jupiter's burst emission returned strong fringes on 1 ms time-scales over channels as narrow as a hundred kilohertz bandwidth.
Conclusions.Long baseline interferometry is confirmed at low frequencies, in spite of phase shifts introduced by variations in ionospheric propagation characteristics. Phase coherence was preserved over tens to hundreds of milliseconds with a baseline of ~700 km. No significant variation with time was found in the correlations and an estimate for the fringe visibility of 1, suggested that the source was not resolved. The upper limit on the source region size of Jupiter Io-B S-bursts corresponds to an angular resolution of ~3 arcsec. Adding remote stations to the LOFAR network at baselines up to thousand kilometers will provide 10 times higher resolution down to an arcsecond.

Key words: instrumentation: high angular resolution -- methods: data analysis -- methods: observational -- techniques: high angular resolution -- planets and satellites: general -- instrumentation: detectors

© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.