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Westerbork and the future of GigaHertz astronomy

The Westerbork Synthesis Radio Telescope (WSRT) has been a powerhouse of science since it began operations in 1968, making more than 50 years of discoveries in radio astronomy happen. Looking forward, we will strengthen our activities in Westerbork on VLBI, GNSS, data releases of the Apertif surveys, and developing next-generation technology for our instruments.

Published by the editorial team, 8 March 2022

The WSRT is part of the EVN: the European Very Long Baseline Interferometry (VLBI) Network, and ASTRON hosts the Joint Institute for VLBI ERIC (JIVE) on its Dwingeloo premises. For the foreseeable future, the WSRT will contribute to the science conducted with the VLBI network of radio telescopes. We hope for many more exciting discoveries, like the whispers that the VLBI network – including one of the WSRT dishes – picked up from the famous fast radio burst FRB20180916B.

An exciting development is the use of one of the dishes in the Global Navigation Satellite System (GNSS) as a reference antenna. Both the WSRT and LOFAR are used in support of the GNSS, particularly to guide performance measurements for the European Galileo system. ASTRON has completed a number of development and demonstration projects together with industry, including ensuring the integrity of the Galileo system for critical Safety of Life services. This has paved the way for the WSRT to be used towards the Galileo Reference Centre (GRC).


Since 1 July 2019, the WSRT has performed the large-scale Apertif surveys. The Apertif receiver that was developed for the surveys has significantly expanded the field of view and the survey speed of the telescope, enabling new, innovative types of astronomical research. The first data release that was shared with the astronomical community in November 2020 has already resulted in many papers with exciting results.

  • Two dozen new Fast Radio Bursts (FRBs; van Leeuwen et al. 2022) were detected, in real time. FRBs were discovered that skewered the halo of M33 (Connor et al. 2020, MNRAS, 499, 4716); multiple repeating FRBs (Oostrum et al. 2020, A&A 635, 61) were studied and, in a unique combination with LOFAR, it was found that some originate from very clean environments, important for cosmological applications (Pastor-Marazuela et al. 2021, Nature 596, 505). The data informed new studies of FRB emission (Bilous et al. 2022 A&A accepted; arXiv:2109.08500), linked in real time to facilities at other wavelengths.
  • The discovery of extremely rapid variability in a radio source (Oosterloo et al. 2020, A&A 641, L4) and more of these rare objects appearing in the Apertif surveys.
  • The serendipitous detection of mega-maser lines in a ultra-luminous infrared galaxy (Hess et al. A&A 647, 193).
  • The Apertif imaging surveys are highly complementary to the surveys now in progress with LOFAR. The potential of combining the Apertif and LOFAR data for the study of radio galaxies is now starting to be explored (Morganti et al. 2021 A&A).
  • The data showed that Apertif had the sensitivity and stability to detect radio counterparts to gravitational-wave signals from double-neutron star mergers (Boersma et al. 2021, A&A, 650, 131).

The next data release will be later this year. The Apertif surveys were ended on 1 January 2022, and with it, the real-time FRB detection system. More imaging data releases will follow as the processing (pipeline) of the data will improve. The richness of these data will lead to more exciting discoveries for decades to come.

As we explore the options to further our footprint in GigaHertz radio astronomy, twelve of the WSRT dishes will be decommissioned at the end of February 2022. Later this year we will explore where we can have scientific impact with our site, given the restrictions of increasing radio frequency interference in the European airspace. The site will remain a testbed for further technological development of our instruments, as marked on our Technology Roadmap, ensuring a future where we will continue to make discoveries in radio astronomy happen.



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