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The Westerbork Synthesis Radio Telescope (WSRT) is a powerful radio telescope that uses a technique called “aperture synthesis” to generate radio images of the sky. The telescope consists of 14 steerable 25m dish antennas and enables astronomers to study a wide range of astrophysics phenomena. The WSRT is an open user facility available for scientists from any country. It is also part of the European VLBI network (EVN) of radio telescopes.

The Westerbork Synthesis Radio Telescope (WSRT)

APERTIF upgrade of WSRT

APERTIF (APERture Tile In Focus), a next generation observing system using focal plane array technology, has been installed on the WSRT in order to significantly expand its field of view and its survey speed, enabling new, innovative types of astronomical research. The WSRT is now an efficient 21cm L-band survey facility. The APERTIF system consists of new Phased Array Feeds (PAFs) that were mounted at the front-end of 12 of the WSRT dishes.

Science with WSRT - APERTIF

Between 2019 and 2021, the majority of the observing time on the WSRT will be dedicated to survey work with APERTIF. Lessons learnt during the operation of the APERTIF system and the scientific insights based on the produced large radio surveys will play a crucial role in preparing the community for the Square Kilometre Array (SKA).


Ten of the dishes have a fixed location, while two at the eastern end of the array can be moved on rails. 1.4 km to the east is a second pair of movable dishes on rails. The array has an east-west linear configuration. In the entire area around the telescope the use of mobile telephones and other sources of radio interference (including automobiles) is prohibited. This is to minimise the undesirable effects of interfering signals.

The radio signal from the sky goes through thick coaxial cables to the main observatory building. In the end, the coaxial cables from all 14 antennas come together in the control room.

The WSRT can also observe together with other radio telescopes in Europe and in the rest of the world. In this way, the WSRT can produce such sharp images that a football on the moon would just be visible.

WSRT Legacy

Since 2016 the APERTIF system is installed at 12 radio telescopes, RT2 to RTD. Telescopes RT0 and RT1 are still equipped with MFFE receivers (modified for circular polarisation) or the 5cm receiver and are used for VLBI observations.

  • Legacy information on the use and analysis of observations with the MFFE equipped WSRT is kept in these webpages. Archival WSRT observations can be requested from
  • The MFFE receivers, and associated backends terminated operations on June 24, 2015. The event was marked with a brief ceremony on that day, , which incidentally was 45 years after the inauguration of the array by Queen Juliana. During the summer of 2015, work the installation of the first 6 APERTIF systems in the WSRT will intensify with the aim to achieve first light in the autumn of 2015.
  • The final call for proposals with the MFFEs was issued with a deadline on Monday 6 Oct 2014. The approved projects, for Semester 14B were observed until the middle of April 2015.

Announcement: WSRT-Apertif Surveys to continue throughout 2021

The large-scale Apertif surveys with the Westerbork Synthesis Radio Telescope (WSRT) that started on 1 July 2019 will continue to be supported during 2021. Read more here.


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