Information AboutLofar |
| CATEGORIES ABOUT LOFAR | |
| radio telescopes | |
| interferometric telescopes | |
| supercomputers | |
|
LOFAR started as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. Astronomical radio interferometers usually consist either of arrays of parabolic dishes (e.g. the One-Mile Telescope ), arrays of one-dimensional antennas (e.g. the Molonglo Observatory Synthesis Telescope ) or two-dimensional arrays of omni-directional dipoles (e.g. Tony Hewish's Pulsar Array ). LOFAR combines aspects of many of these earlier telescopes -- in particular it uses the omni-directional dipole antennae as a phased array using the Aperture Synthesis technique developed in the 1950s. Like the earlier CLFST low-frequency radio telescope, the design of LOFAR has concentrated on the use of large numbers of relatively cheap antennas, with the mapping performed using Aperture Synthesis software. The electronic signals from the LOFAR antennas are digitised, transported to a central digital processor, and combined in software in order to map the sky. 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 - 25000 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 ultimately 350 km in diameter. (In phase 1 that is currently funded 15000 antenna's and maximum baselines of 100 km will be built). Data transport requirements are in the range of many Tera-bits/sec and the processing power needed is tens of Tera-FLOPS. The mission of LOFAR is to survey the universe at radio frequencies from ~10 – 240 MHz with greater Resolution and greater sensitivity than previous surveys, such as the 7C and 8C surveys, and surveys by the Very Large Array (VLA) and Giant Meterwave Radio Telescope (GMRT) . LOFAR will be the most sensitive radio observatory until the next generation of large array radio telescope, the Square Kilometre Array ( SKA ), comes online around 2020 . SCIENCE CASE The sensitivities and spatial resolutions attainable with LOFAR will make possible several fundamental new studies of the Universe as well as facilitating unique practical investigations of the environment of the earth.
Much LOFAR science builds on fundamental areas of research that have been pursued intensively or pioneered within the Netherlands during the last half century. Key projects
TIMELINE LOFAR was proposed to ASTRON in 1997. A feasibility study was carried out and international partners sought during 1999. In 2000 the Netherlands LOFAR Steering Committee was set up by the ASTRON Board with representatives from all interested Dutch university departments and ASTRON. In November 2003 the Dutch Government allocated 52 Million Euro to fund the infrastructure of LOFAR under the Bsik programme. In accordance with Bsik guidelines, LOFAR was funded as a multidisciplinary sensor array that will facilitate research in geophysics, computer sciences and agriculture as well as astronomy. In December 2003 LOFAR's Initial Test Station (ITS) became operational; this was an important milestone in the LOFAR development. The ITS system consists of 60 inverse V-shaped dipoles; each dipole is connected to a low noise amplifier (LNA), which provides enough amplification of the incoming signals to transport them over a 110 m log coaxial cable to the receiver unit (RCU). On April 26 2005 , an IBM Blue Gene -L Supercomputer was installed at the University Of Groningen 's math center, for LOFAR's Data Processing . This is now the 2nd most powerful supercomputer in Europe , after the MareNostrum in Barcelona {Link without Title} . In July 2006 the first LOFAR station (''Core Station 1'', aka. CS1) will be put in the field using pre-production hardware. A total of 96 dual-dipole antennas (the equivalent of a full LOFAR station) will be grouped in 4 clusters, the central cluster with 48 dipoles and other three clusters with 16 dipoles each. The clusters will be distributed over an area of ~500m in diameter. EXTERNAL LINKS |
|
|