WSRT - astronomers

WSRT in the morning

The Westerbork Synthesis Radio Telescope is one of the most powerful radio observatories in the world. It enables astronomers to study a wide range of astrophysical problems: from pulsars to kinematics of nearby galaxies to the physics of black-holes.

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. This allows the astronomers to obtain some of the sharpest and more detailed images possible in astronomy.

The APERTIF system in the WSRT

The WSRT is currently being transformed into an efficient 21cm L-band survey facility by replacing the front-ends in 12 telescopes by Phased Array Feeds (PAFs). Operations with the Multi-Frequency-Frontend (MFFEs) receivers and associated backends terminated on June 24, 2015.

The APERTIF system significantly increases the field of view and thereby the survey speed of the WSRT. This upgrade is expected to be completed by the end of 2016.

Announcement of Opportunity for WSRT APERTIF Surveys

The majority of the observing time from 2017-2020 will then be dedicated to survey work and APERTIF will be used to carry out a limited number of surveys. These surveys will be defined on the basis of the
science interests expressed by the community and the technical capabilities of the operational system.

The ASTRON Radio Observatory and the APERTIF Survey Team have put together two documents which are available at:

These documents describe the process and requirements for interested parties to join the APERTIF survey team. They also detail a number of draft surveys that have been defined after community input and will be
further developed to form the APERTIF Survey Program, again in close collaboration with the community. We invite parties interested in joining the APERTIF Survey Team to contact us using the contact details
listed in the documents.

With the experiences made in the operation of such systems and in the scientific exploit of large radio surveys, the WSRT will play a crucial role in the preparation of the Square Kilometer Array (SKA).



  • Announcement of Opportunity for WSRT APERTIF surveys (follow the link: ) 29 July 2015.
  • 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 Julliana.  During the summer of 2015, work the installation of the first 6 APERTIF systemsin 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.
  • The latest deadline of regular proposals for the WSRT was at Friday 27 September (2013), 14:00 CEST (12:00 UTC). For more details please see the latest call for proposals.
  • Service Proposal admission: These can be submitted at any time, and can usually request up to 26 hours of telescope time. They are intended for quick verifications, pilots, acquisition of some ancillary data, etc., and, if approved, will receive "filler" priority for the running semester, without any guarantee of being carried out.
  • The dishes RT2, RT4, RT5 are used as a testbed for Apertif focal plane array developments, and are unavailable for regular astronomical observing since semester 12A. The overall sensitivity of the array will be correspondingly reduced to that of a 10-antenna array, but the uv-coverage will not be significantly impacted for most projects.

  • The WSRT LFFE receivers, covering 115 - 180 MHz, have been decommissioned and are not available anymore. LOFAR offers much more extensive capabilities in this band.

The NL PC proposal submission system Northstar

is accessible through a WEB-BASED INTERFACE.

First time users

should take note of this Instruction link
The web proposal tool is directly accessible through the Web Proposal Link

Unevenly distributed oversubscription

usually prevails; proposers significantly enhance their chances for success if they can tailor their programmes. Oversubscription rates at LST=12-18 are typically a factor of 3 to 5, due to the demand for long integrations on targets at high northern Galactic latitudes (RA=10 to RA=14) and in the inner Galaxy (RA=17 to RA=21). On the other hand, LST=00-06 may have an oversubscription of only 1 to 2, barring occasional large requests. In addition, projects which can be broken into small segments and do not need perfect HA coverage can be scheduled more flexibly, and are thus at an advantage, even if they need a large total integration time. Stringent demands for night-time 12-hr observing runs can only be met during limited periods, and are thus less likely to be scheduled.

Service Proposals

can be submitted at any time between deadlines, and can usually request up to 26 hours of telescope time. They are intended for quick verifications, pilots, acquisition of some ancillary data, etc., and, if approved, will receive "filler" priority for the running semester, without any guarantee of being carried out. 

Urgent Proposals

can submitted at any time between deadlines. They will be assessed on scientific excellence just like regular proposals, and must in addition demonstrate why the project could not be submitted before the last deadline and cannot wait for the next semester.

Support for European proposals

is available via the Trans-National Access programme of the RadioNet Consortium. The WSRT would like to encourage proposals from groups in which both the PI and at least 50% of the team members on the proposal are based in an EU or affiliated country other than The Netherlands (for specifics, see Such projects benefit both the WSRT and the eligible groups. They are entitled to reimbursement for a data analysis visit by one of their members to ASTRON; a staff member can be assigned for support at all stages from proposal writing to final data analysis. The WSRT hopes proposers are willing to take note of the EU encouragement to give their teams a European dimension; it brings valuable support!


Astronomers can send technical inquiries and requests for support by e-mail to wsrt-support [at] astron [dot] nl, where they will be answered or forwarded as needed.

Design: Kuenst.    Development: Dripl.    © 2015 ASTRON