LOFAR

Phased arraysaperture arrayFixed antennas (often simple dipoles) combined electronically rather than steered mechanically, so a beam can point anywhere, and many at once. Used at low frequencies by LOFAR and SKA-Low. of dipole antennas (Low Band 10–90 MHz, High Band 110–240 MHz) in over 50 stations, 38 in the Netherlands and the rest across Europe, correlated digitally on baselinesbaselineThe separation between two antennas of an interferometer, projected onto the plane perpendicular to the source. Long baselines give fine resolution; short ones recover extended emission. up to about 2,000 km. Multi-beaming and a wide field make it efficient at the lowest frequencies observable from the ground: steep-spectrum emission from AGN lobes, cluster haloes and relics, pulsarspulsarA rotating, magnetised neutron star whose beamed emission sweeps past Earth once per turn. Millisecond pulsars, spun up by accretion, keep time to tens of nanoseconds over decades. and the epoch of reionisationepoch of reionisationThe period, roughly 150 million to 1 billion years after the Big Bang (z ≈ 20–6), when the first stars and galaxies ionised the neutral hydrogen filling the Universe. Probed by redshifted 21 cm emission and high-z galaxies..

Operator

ASTRON, LOFAR ERIC

Site

Netherlands and stations across Europe

Passband

10 MHz – 240 MHz

Opening

2010