The Low Frequency Array, the world's largest distributed radio telescope

The Low Frequency Array, is a multi-purpose sensor array. Its main application is astronomy at low radio frequencies (10-240 MHz). LOFAR consists of an array of antenna fields distributed throughout the Netherlands and several neighbouring countries. The maximum resolution of an telescope is determined by its diameter. The largest single dish radio telescopes have diameters of several hundred meters at most. Radio interferometers combine the signals of several single dish telescopes to achieve a resolution higher than possible with single dish.

With the advances in information technology, it is for the first time possible to fully process the signals of radio interferometers operating at low radio frequencies with digital electronic components. LOFAR is the first telescope which utilizes digital components for real time processing of the signals in a large telescope array.

Instead of dishes LOFAR uses arrays of dipole antennas. This allows to achieve a large collecting area for radio waves for each of the elements of the radio interferometer. Those phased arrays still have a pointing direction (similar to a dish), however, phased arrays can point to several directions at the same time, in contrast to dishes. 

LOFAR consists of 38 stations in the Netherlands, six stations in Germany, three in Poland, one station each in France, UK, Sweden, Ireland, and Latvia. The signals of the LOFAR stations are transferred to a central processing unit via high speed internet connections. Each station can send data with a rate up to 4 Gibabyte per second. The signal of all stations needs to be processed (correlated) in real time for an interferometric observation. This requires fast and reliable network connections and very fast central processing unit with very high input and output rates. Recently, a dedicated GPU-cluster has been developed for this task. 


The International Lofar Telescope (ILT)

LOFAR is operated as a fully international facility, to which end the International LOFAR Telescope has been formed. It is a Foundation under Dutch law, and has board members from LOFAR consortia in each of the countries where LOFAR stations are located or are planned to be build. The data taken by the stations are transported by dark fiber to the central processing unit, which is hosted at the University of Groningen.


Partners of the International LOFAR Telescope






The German Long Wavelength Consortium  (GLOW)

The German Long Wavelength Consortium (GLOW) was formed 2006 by German universities and research institutes to foster the use of the radio spectral window at meter wavelengths for astrophysical research. The consortium has 15 partners and runs six international LOFAR stations . The German stations can perform standalone observing programs, which are focused currently on long-term pulsar monitoring observations.



Further Reading

Überblick und Funktionsprinzip des LOFAR Radioteleskops (in German)

The LOFAR 2.0 project - A LOFAR upgrade

LOFAR page at ASTRON, the Netherlands Institute for Radio Astronomy (Astron web pages)

LOFAR in the 'Landschaft der Forschungsinfrastrukturen' of the German Federal Ministry of Education and Research (BMBF web pages)