Low frequency array
LOFAR (abbreviation for Lo w F requency Ar ray ) is a radio interferometer , ie an array of many radio telescopes , whose signals are combined into a single signal. In order to achieve an angular resolution of one arcsecond and better with LOFAR, an extension over the size of the Netherlands is not enough, so it was decided to expand LOFAR to include stations spread across the European continent. At the time of its official inauguration by Queen Beatrix of the Netherlands on June 12, 2010, the telescope had around 10,000 individual antennas across Europe, and around 1000 more had been added by 2014. The detectable frequency ranges include 10–80 MHz and 110–240 MHz, leaving out the VHF range, in which no radio astronomical measurements are possible in Europe.
LOFAR is a joint project of the Dutch astronomical organization ASTRON, the universities of Amsterdam , Groningen , Leiden and Nijmegen, as well as a German participation consisting of twelve institutes that have joined together in the German Long Wavelength Consortium (GLOW). It owns the Leibniz Institute for Astrophysics Potsdam (AIP) with the OSRA , the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn , the Max Planck Institute for Astrophysics (MPA) in Garching , the Excellence Cluster Universe Munich / Garching , the Thuringian State Observatory in Tautenburg , the Jacobs University Bremen and the universities of Bielefeld, Bochum, Bonn, Hamburg, Cologne and Würzburg. The proposal for LOFAR came from George K. Miley in 1997 . Heino Falcke is one of the leading scientists .
The stations, each consisting of 192 individual antennas, are located at various locations in the Netherlands , Germany and other European countries (France's Nançay radio telescope , Great Britain, Sweden). Further stations in Poland, Ireland and Finland are planned. In the case of the LOFAR, the individual antennas are very simply built wire pyramids and less than a man's height - in contrast to earlier interferometers such as the Very Large Array and the VLBI , in which the individual components are large parabolic antennas.
The low cost of the antennas makes it possible to provide a large number of them. The collection area of the entire network is around 0.5 square kilometers today, with an extension of more than 1000 kilometers. The first Dutch prototype station was in 2006 at Exloo in the province of Drenthe . 38 stations have been in operation in the Netherlands since 2014. This largest radio telescope in the world, which is supposed to provide wide views into space and insights from the time shortly after the Big Bang, was inaugurated in June 2010. The first German station went into operation in November 2007 next to the 100-meter radio telescope Effelsberg . Five further stations in Unterweilenbach / Garching, Tautenburg (Thuringia), in Bornim near Potsdam, in Jülich and in Norderstedt near Hamburg followed until 2014. One station each was in Great Britain (Chilbolton), in France on the site of the Nançay radio telescope and in Sweden (Onsala) built. Regular observations began in December 2012.
The main factor that will determine the performance of the system is a central computer in the computer center of the University of Groningen (Netherlands) until 2013, IBM 's Blue Gene - supercomputer with a capacity of 37 teraflops, since 2014, the computer cluster COBALT, which the individual signals of the various Antennas offset against each other, as well as a very fast data communication network ( Wide Area Network - WAN). For the first German station in Effelsberg, a separate fiber optic cable with 10 Gigabit / s was laid to the Max Planck Institute for Radio Astronomy in Bonn. From there, the data is forwarded to the Jülich research center via the German research network DFN and then via the Dutch SURFNET to the central computer cluster.
LOFAR's scientific goals were developed in six international key science projects led by Dutch, German and British institutes. The aim is to search for signals from the reionization epoch from around 1 billion years after the Big Bang at frequencies between 120 and 200 MHz. Catalogs of radio sources at five frequencies are to be created. Other objects are pulsars and radio signals from particles of cosmic rays that penetrate the earth's atmosphere. The Max Planck Institute for Radio Astronomy in Bonn is leading a key science project to study cosmic magnetic fields. The Leibniz Institute for Astrophysics Potsdam has taken over the management of the key science project for measuring radio radiation from the sun .
In addition to physical knowledge about galaxies , quasars and matter from the earliest times of the universe, the operators hope to gain knowledge of how a future, more powerful Internet should be designed. In addition, LOFAR is a forerunner of the planned Square Kilometer Array , a radio telescope with a square kilometer of collecting area, which will be built in 2017 as a global joint project in Australia and South Africa and will work from around 70 MHz to at least 10 GHz from 2020.
The array will also be used for other purposes in the Netherlands. For example, the systems could be equipped with wind sensors in order to be able to make very precise wind forecasts with the data obtained. This is important for wind farms , for example . Furthermore, seismic sensors can be connected to the antennas so that exact measurements of seismic activity are also possible.
Web links
- LOFAR
- LOFAR in Germany
- German Long Wavelength Consortium (GLOW)
- LOFAR station in Effelsberg
- LOFAR Leibniz Institute for Astrophysics Potsdam
- LOFAR MPA Garching
- Solar physics and space weather
- Key Science Project Cosmic Magnetism
- SKA
literature
- M. Hoeft, R. Beck: LOFAR is running! In: Stars and Space . No. 6 . Spectrum, 2010, ISSN 0039-1263 ( PDF ).
- H. Falcke, R. Beck: With software to the stars . In: Spectrum of Science . No. 7 . Spectrum, 2008 ( PDF ).
- R. Beck, W. Reich: LOFAR: Starting signal for German stations . In: Stars and Space . No. 9 . Spectrum, 2006, ISSN 0039-1263 ( PDF ).
- R. Beck: The Square Kilometer Array . In: Stars and Space . No. 9 . Spectrum, 2006, ISSN 0039-1263 ( PDF ).
- G. Heald, et al .: Low frequency radio astronomy and the LOFAR Observatory. Springer, Cham 2018, ISBN 978-3-319-23433-5 .