About LOFAR

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Oude Hoogeveensedijk 4
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Astron

Initiator: ASTRON Netherlands Institute for Radio Astronomy

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This project was co-financed by the EU, the European Fund for Regional Development and the Northern Netherlands Provinces (SNN), and EZ/KOMPAS.

First international LOFAR station in Effelsberg

The Max Planck Institute for Radio Astronomy has teamed up with The Netherlands Institute for Radio Astronomy, ASTRON, to realise the first international telescope station of the LOFAR radio telescope. LOFAR is the LOw Frequency ARray, initiated by ASTRON with stations centred on Exloo in the northeast of The Netherlands, and is now becoming an international project that will encompass stations in many European countries. The first international LOFAR station (IS-DE1) was completed on the area of the Effelsberg radio observatory next to the 100-m radio telescope of the Max Planck Institute for Radio Astronomy. On 20 November 2007, the formal handover and acceptance of the LOFAR station took place in Effelsberg between representatives from ASTRON and MPIfR. This official moment marks the start of systematic observations.

LOFAR is a new concept radio telescope. It is the first digital radio telescope that does not employ any moving parts. At low frequencies between 20 MHz and 80 MHz (wavelengths of several meters) at which LOFAR works, each antenna of LOFAR observes cosmic radio waves from the full sky. The viewing direction and field of view of aLOFAR station are not determined mechanically as in conventional radio telescopes, but are electronically steered when combining signals from the 96 single antennas of a station and from the different stations. LOFAR will also have antennas operating at radio frequencies between 120 MHz and 240 MHz. A central supercomputer (IBM BlueGene/L hosted by the University of Groningen, NL) receives all digital signals together. This enables the observer to simultaneously peer into multiple directions on the sky at the same time, thus permitting many different observing programmes to be conducted at the same time. This greatly increases the productivity of the instrument.

LOFAR has been developed by ASTRON, which has had the first LOFAR station, CS1, in operation at Exloo (NL) since 2006, and will be rolling out a minimum of 36 stations in The Netherlands with well over 25000 individual antennas over the next two years.

The investigation of details of the various sources of cosmic radiation that LOFAR will be sensitive to in the the sky (e.g. exploding stars, distant galaxies and quasars hosting supermassive black holes),requires an angular resolution that is better than an arcsecond. This will be achieved by connecting the stations in the Netherlands, in Germany and soon also in other European countries (e.g. UK, France and Sweden) via high speed, cross-border optical fibre links. In November 2007, Effelsberg has taken an important step towards such a connection by installing a fibre cable between the observatory in Effelsberg and the institute in Bonn, and by connecting to the German high speed network to transfer the data to the LOFAR supercomputer (IBM BlueGene/L) at the University of Groningen.

The image of the whole radio sky as shown in figure 1 was measured using only the antennas of the LOFAR station in Effelsberg. In a second of observation time, it is possible to detect the whole sky as if with a fish-eye lens and to show not only the Milky Way but also other discrete sources (Cygnus A, Cassiopeia). This observation from 29 October 2007 represents the 'first light' for the LOFAR station in Effelsberg and the start of astronomical observations of this station. This demonstrates the capability of LOFAR to monitor the sky for possible changes on short time scales.

On Tuesday, 20 November 2007, the official handover of the LOFAR station Effelsberg took place. The station is thus the first international station of the LOFAR project (with the abbreviation IS-DE1) and after the Netherlands station CS1, only the second LOFAR station to come online so far. At a meeting in the radio observatory Effelsberg, the location of the station, Mark Bentum (ASTRON), rollout manager of the LOFAR project from The Netherlands, and Wolfgang Reich, LOFAR project manager for the MPIfR, signed the handover agreement. Further collaboration between ASTRON and the MPIfR in all technical and scientific matters of the project takes place in the framework of a Memorandum of Understanding that was signed in 2006.

Figure 1: The radio sky above Effelsberg on 29 October 2007 as observed in only one second. First image with all 96 LOFAR antennas in Effelsberg at 42 MHz (7 metre wavelength). Image: Stefan Wijnholds, ASTRON, Peter Müller, MPIfR (Please click for higher resolution).

Figure 2: The first international station of the low frequency radio telescope LOFAR (IS-DE1) in close proximity to giant the 100-m radio telescope. A part of the 96 dipole antennas of the LOFAR station Effelsberg can be seen in the foreground. Photo: Wolfgang Reich, MPIfR (Please click for higher resolution image).

Following the start of the measurements with the LOFAR station in Effelsberg, it is only a matter of time before the first observations at high resolution for detailed investigations of the radio Universe through connection over fast data links become routine. The researchers at the Max Planck Institute for Radio Astronomy are particularly interested in magnetic phenomena in the Universe and have taken the lead in this international research programme. With LOFAR, a new age has dawned and research of the Universe at the very longest wavelengths of the electro-magnetic spectrum has begun. LOFAR will attract astronomers from all over the world, eager to explore this little-explored frequency range for studies ranging from highly energetic phenomena in the Earth's upper atmosphere, through the nearest planets, to the extremely distant first stars and galaxies forming at the earliest observable times in the Universe.

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Further information and images:

- Signing the Acceptance at the start of the observations with the first international LOFAR station (IS-DE1)     on 20 November 2007. The photo shows Wolfgang Reich (left) and Mark Bentum (right) immediately after     signing the acceptance in the library of the radio observatory Effelsberg.
- The LOFAR sky from Effelsberg, ASTRON/JIVE Daily Image, November 15, 2007.
- MPIfR (Max-Planck-Institut für Radioastronomie) and ASTRON (Netherlands Foundation for Research in         Astronomy), partners in the LOFAR project.
- Homepage LOFAR in Germany (in German).
- Homepage LOFAR international.

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LOFAR is funded by the Netherlands government in the BSIK programme for interdisciplinary research for improvements of the knowledge infrastructure. Additional funding is being provided by the European Community, European Regional Development Fund and the “Northern Netherlands Assembly (SNN)” EZ/KOMPAS.

ASTRON is an institute of the Netherlands Organization for Scientific Research, NWO.

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More information:

Rene Vermeulen, directeur Radiosterrenwacht ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, tel. 0521 595100, rvermeulen [at] astron [dot] nl.

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ASTRON initiated LOFAR as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. 
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