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Radio telescope gets double vision

Using an electronically steered radio telescope, ASTRON has demonstrated the ability to multi-task astronomical observations by pointing one telescope in two completely different directions simultaneously. This demonstration is an important step forward for the SKA (Square Kilometre Array) project and ushers in the era of large, software-driven radio telescopes at centimetre wavelengths. The new multi-tasking capability radically changes the way astronomers currently work and its potential to realise ground-breaking astronomical discoveries is enormous.

Published by the editorial team, 23 March 2011

An international team, led by ASTRON, achieved this milestone by developing innovative technologies, which will be crucial for constructing the next generation of radio telescopes. These observations were done using a prototype radio telescope named EMBRACE (European Multi-beam Radio Astronomy Concept), which is based on a radically different design than conventional radio telescopes. The success of simultaneous observations in multiple directions displays the utility of such methods for SKA, a giant, international radio telescope that will be built in the next decade in the southern hemisphere. ASTRON is one of the leading institutes in the development of the SKA.

Instead of using costly, conventional parabolic dishes, that have a receiver at the focal point, EMBRACE combines many small antennas, each with its own receiver, to synthesise a giant telescope. The various signals received at the antennas are combined in such a way as to allow the telescope to be electronically, instead of mechanically steered. One of the greatest advantages of this method is the capability it gives to point the telescope in multiple directions simultaneously. “Various institutes in the world are working on design concepts for the SKA. An international team led by ASTRON is the first to successfully demonstrate that it is possible to perform two observations in parallel using an electronically steered telescope.”, said Dion Kant, Project Leader for EMBRACE.

The EMBRACE telescope was designed in the framework of the SKA Design Study (SKADS) program, which is financed via the European Commission (FP6) and participating European institutes. The EMBRACE project is a collection of partners from the Netherlands, France, Italy, and Germany. In addition to the EMBRACE prototype located in Westerbork, the Netherlands, there is a similar test system in Nançay, France, where similar experiments are also being undertaken. The experience being gained by these teams is crucial input for the design of the SKA.

Caption to image at the top of the page:

EMBRACE was used to do two observations near 1.4 GHz simultaneously by phasing the EMBRACE aperture array elements in such a way to form two beams on the sky at the same time. One beam was used to track a pulsar (right) while the other beam was scanning over the sky to image the neutral hydrogen along the Milky Way (left). The figure shows the results of these observations: the pulse profile of the pulsar detected and the longitude-velocity diagram of the neutral hydrogen along the Galactic plane (with the double structure indicating spiral arms of the Galaxy). Credits: the EMBRACE team, ASTRON.

Smaller images:

These are the separate images incorporated in the one at the top of the page. Click on the images for a high resolution version. Credits: the EMBRACE team, ASTRON.

For more information, please contact:

Dr. Ir. Albert-Jan Boonstra, head of the R&D department. Phone: (+31)(0)521 595 100. E-mail:

Femke Boekhorst, PR & Communication. Phone: (+31)(0)521 595 204. E-mail:


Caption to the image above: the image shows the dual beams of EMBRACE detecting a pulsar and the Milky Way. On the bottom you can see the EMBRACE antennas that are located in a radome near the Westerbork Synthesis Radio Telescope.

More information about pulsars and the milky way:

Pulsars are cosmic light-houses that allow us to study gravity and particle physics. They are burned-out stars, approximately as massive as the Sun, which were squeezed by their own gravitational self-attraction into a ball roughly 15 kilometres wide. Pulsars have incredibly strong magnetic fields. They also spin very rapidly around their rotational axis, sometimes as much as several hundred times a second. Pulsars emit narrow beams of radio waves from their magnetic poles, which sweep past the Earth as the star rotates, creating the characteristic repeating pulses that pulsars are famous for.

In addition to containing many billions of stars, our Milky Way galaxy also contains a tremendous amount of dust and gas. A significant fraction of this interstellar gas is in the form of neutral hydrogen, which can be observed with the help of a radio telescope. One of the big advantages of observing hydrogen gas with a radio telescope is that it is possible to precisely measure how this gas is moving in space. This allows astronomers to make 3-D maps of galaxies, including our own Milky Way.



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