LOFAR picks up speed
First international LOFAR station in Effelsberg starts 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 (e.g. stars, galaxies and quasars) 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.
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.