LOFAR (LOw Frequency ARray) is a low-frequency radio interferometer composed by observational stations spread across Europe, utilizing a novel phased-array antenna design and an innovative computer and network infrastructure to handle the collected extremely large data volumes. It covers the largely unexplored low-frequency range from 10-240 MHz with an unprecedented sharpness.
LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA).
LOFAR uses a new approach to obtain 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 centres of active galactic nuclei. The LOFAR array records the incoming signals at a very high data rate, and then uses the power of supercomputers to correlate the separate signals to create maps of the sky. Among the objectives of the project is the detection of diffuse neutral hydrogen clouds during the epoch of recombination of the intergalactic gas.
The LOFAR radio telescope is an international telescope operated by ASTRON
Technology
LOFAR is based on an array of simple omni-directional antennas, instead of mechanical signal processing with a dish antenna, that are connected to each other with a large Information and Communication Technology infrastructure. There are two types of antennas at each station: the High Band Antennas (HBA, 110-240 MHz) and Low Band Antennas (LBA, 10-90 MHz). To make radio pictures of the sky with adequate sharpness, these antennas are to be arranged in clusters that are spread out over Europe. In total there are around 8,000 antennas in several countries, including the Netherlands, France, Germany, Ireland, Poland, Sweden and the UK, comprising, since 2019, almost 51 individual stations. The electronic signals from the antennas are digitised, transported to a central digital processor, and combined in software to emulate a conventional antenna.
Data transport requirements are in the range of many Tera-bits/sec and the processing power needed is tens of Tera-FLOPS.
The project (NenuFAR) has built a separate super-station in Nancay which will greatly increase the sensitivity of LOFAR.
With LOFAR.IT plans, INAF envisages to acquire a LOFAR 2.0 Station to be installed in Medicina (Bo) by 2021-22.
Science
The LOFAR telescope, combining unprecedented fields of view with high sensitivity and the ability to access previously unexplored wavelength regimes, allows astronomers to engage in multiple lines of research at once: they can look back the so-called ‘Dark Ages’, billions of years to a time before the first stars and galaxies were; they can obtain surveys of vast areas of the low-frequency radio sky; they can detect radio transients originating from highly energetic explosions in the universe.
Main key science with LOFAR:
- Epoch of Reionization (EoR), is the period during which the neutral gas in the Universe was completely ionised by the first stars and galaxies.
- Deep extragalactic surveys
- Transient sources and pulsars
- Ultra-high energy cosmic rays
- Solar science and space weather
- Cosmic magnetism
- Multi-frequency Snapshot Sky Survey (MSSS), is a radio survey, imaging the northern celestial hemisphere using the LOFAR low and high frequency bands.
Operations
The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community.
LOFAR.IT consortium, lead by INAF, with the Department of Physics of the University of Turin as a member, has the aim to provide italian scientists the optimal conditions for LOFAR data access and analysis in order to optimize the research scientific impact.