ASTRONThe Netherlands Radio Astronomy Facility


Dr. Marco de Vos
Oude Hoogeveensedijk 4, 7991 PD Dwingeloo
+31 591-595247

The Netherlands Radio Astronomy Facility comprises two telescopes: the LOw Frequency ARray (LOFAR) and the Westerbork Synthesis Radio Telescope (WSRT) which together offer observing capabilities across radio frequencies of 10 MHz to 5 GHz . The Facility results from a long history of innovative systems development by ASTRON in partnership with the wider Dutch University community. Today, the Facility provides the platform from which the Netherlands continues to lead world-class discoveries and innovation in radio astronomy.

Astronomers use these telescopes to study phenomena incl. mapping our galaxy, timing pulsars, tracing cosmic structure and probing the evolution of the Universe itself.

The Netherlands Radio Astronomy Facility (“National Facility”) comprises two telescope arrays: the LOw Frequency ARray (LOFAR) and the Westerbork Synthesis Radio Telescope (WSRT) whose capabilities are aligned with a number of core themes of the Nationale Wetenschapsagenda (NWA). Both LOFAR and WSRT are established, offering outstanding observing capabilities from 10’s of MHz to 5 GHz. We present these two arrays for inclusion on the Roadmap as the singular National Facility infrastructure that will be seeking investment in the coming period (2020-2025). LOFAR, the LOw Frequency ARray, was conceived in the early 2000’s and realised by ASTRON. LOFAR comprises large sets (‘stations’) of simple, static dipole antennas. LOFAR is one of a new series of ‘software telescopes’ relying on intensive, high-throughput processing to interpret the complex sky response of tens of thousands of receptors. LOFAR has been fully operational for 7 years, and has an expected scientific operating lifetime beyond 2030 given the in-progress, funded “LOFAR2” upgrade program.

Researchers from around the world use LOFAR for a huge variety of astronomical studies, spanning investigations into the Earth’s weak current lightning storms, mapping space weather events, our galaxy in detail, pulsars, cosmic structure and the first formation (‘birth') of galaxies themselves. In the 2020’s LOFAR’s wide science remit will continue, along with spending a major part of its observing time mapping the radio sky in unprecedented detail at 55 MHz and 150 MHz.

The Westerbork Synthesis Radio Telescope was established in 1968 and now comprises 14, 25-metre equatorial dish antennas. The WSRT dishes lie along an east-west track, of length (baseline) 2.7 km and sited in an area with significant radio frequency interference protection due to both local legislation and the relatively remote location. The WSRT has maintained world-leading cm-wavelength astronomy capabilities with a focus on studies of neutral Hydrogen (HI). The WSRT is a significant research infrastructure: it has secured participation in the European VLBI network.

Both WSRT and LOFAR have accumulated significant astronomical data repositories. The value of these data increases with the exploitation of multi-wavelength and multi-messenger astronomy. Long term preservation of the data is vital, along with increasingly sophisticated analysis tools.

The upgrade to this National Facility is demanded to increase the GHz capabilities to extend far beyond the current (WSRT) limit of about 5 GHz. This limit is imposed by the nature of the WSRT (mesh wire) dishes. In the 2020’s the options are to move to a clear-aperture (offset focus design) panelled dish antenna or consider a dense, static ground-based aperture array (as is trialled by ASTRON in the Ministry of Defence project “DISTURB”).

Whilst the Netherlands astronomical community benefits from access to a large suite of world-leading telescopes sited overseas, there are good reasons to maintain a National Facility as is most recently recognised in Minister Van Engelshoven’s letter to The House of Representatives, as the response to the Rathenau Institute report (9 December 2019): the report highlights LOFAR as a Dutch-based infrastructure yielding high revenues.

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