LOFAR: The LOw-Frequency ARray

¹ Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
² Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
³ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
⁴ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁵ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁶ Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
⁷ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁹ School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
¹⁰ Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, 85741 Garching, Germany
¹¹ Onsala Space Observatory, Dept. of Earth and Space Sciences, Chalmers University of Technology, 43992 Onsala, Sweden
¹² International Centre for Radio Astronomy Research – Curtin University, GPO Box U1987, WA 6845 Perth, Australia
¹³ STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK
¹⁴ Institute for Astronomy, University of Edinburgh, Royal Observatory of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁵ LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris Diderot, 92190 Meudon, France
¹⁶ Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁷ Leibniz-Institut fr Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹⁸ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
¹⁹ Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
²⁰ Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
²¹ Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
²² Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, CNRS/Université d’Orléans, LPC2E UMR 7328 CNRS, 45071 Orléans Cedex 2, France
²³ Center for Information Technology (CIT), University of Groningen, The Netherlands
²⁴ Radio Astronomy Lab, UC Berkeley, CA 94720, USA
²⁵ Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon, 9 av. Charles André, 69561 Saint Genis Laval Cedex, France
²⁶ Mt. Stromlo Obs., Research School of Astronomy and Astrophysics, Australian National University, A.C.T. 2611 Weston, Australia
²⁷ CSIRO Australia Telescope National Facility, PO Box 76, NSW 1710 Epping, Australia
²⁸ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
²⁹ Chalmers University of Technology, 412 96 Gothenburg, Sweden
³⁰ Observatoire de la Côte d’Azur, Département Lagrange, Boulevard de l’Observatoire, BP 4229, 06304 Nice Cedex 4, France
³¹ Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, 18330 Nançay, France
³² Netherlands eScience Center, Science Park 140, 1098 XG Amsterdam, The Netherlands
³³ Centrum Wiskunde & Informatica, PO Box 94079, 1090 GB Amsterdam, The Netherlands

Received: 7 December 2012
Accepted: 9 May 2013

Abstract

LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10–240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. 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’s new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory.