ENGINEERING

On Saturday afternoon, the Queen of the Netherlands opened the largest radio telescope in the world, LOFAR in Borger-Odoorn (Drenthe). The new LOFAR telescope has been built according to a completely new concept. No large dishes are used, but large numbers of small antennas.

7,000 antennas are spread over 44 fields in the North of the Netherlands and from Sweden to France and from the UK to the East of Germany. Glass fibres connect the antennas with a supercomputer at the University of Groningen's Computer Centre. In this way, a giant telescope is formed with a diameter of one hundred to one thousand kilometres.

The telescope researches, among other things, the earliest Universe, cosmic particles and magnetism in the Milky Way and other galaxies. LOFAR is also used for research in the area of geophysics, precision agriculture and ICT. While the antennas observe the sky, underground sensors collect date about the structure of the Earth. These data contribute to better models for the Earth, water management and gas exploitation.

LOFAR started as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. The basic technology of radio telescopes had not changed since the 1960's: large mechanical dish antennas collect signals before a receiver detects and analyses them. Half the cost of these telescopes lies in the steel and moving structure. A telescope 100x larger than existing instruments would therefore be unaffordable. New technology was required to make the next step in sensitivity needed to unravel the secrets of the early universe and the physical processes in the centers of active galactic nuclei.

LOFAR is the first telescope of this new sort, using an array of simple omni-directional antennas instead of mechanical signal processing with a dish antenna. The electronic signals from the antennas are digitisd, transported to a central digital processor, and combined in software to emulate a conventional antenna. The cost is dominated by the cost of electronics and will follow Moore's law, becoming cheaper with time and allowing increasingly large telescopes to be built. So LOFAR is an IT-telescope. The antennas are simple enough but there are a lot of them - about 7000 in the full LOFAR design. To make radio pictures of the sky with adequate sharpness, these antennas are to be arranged in clusters that are spread out over an area of 100 km in diameter within the Netherlands and over 1500 km throughout Europe. Data transport requirements are in the range of many Tera-bits/sec and the processing power needed is tens of TeraFLOPS.