LOFAR: A digital aperture array radio telescope

Construction of the Low Frequency Array (LOFAR) is nearly complete. It consists of 48 stations, mostly concentrated within the Netherlands, and spreading into Europe. Each station has 48 or 96 dipole antennas and antenna tiles, optimized for 30–240 MHz. LOFAR uses a combination of true time delay and phased-array techniques. Digital beam-forming gives the system agility and allows rapid repointing and the potential for multiple simultaneous observations. Digital buffering allows a posteriori imaging of transient events. LOFAR has automated processing pipelines interacting with its long-term archive. In all its aspects LOFAR is an important pathfinder for the SKA.