© ASTRON

The Users Meeting was followed on Tuesday by a two day LOFAR Community Science Workshop where over 120 members of the LOFAR collaboration came together to present their latest science results and share ideas and experiences about doing science with LOFAR. An amazing range of results were presented including new record-breaking sub-arc imaging with LOFARs international baselines, first extragalactic detections of Carbon radio recombination lines (RRLs), the first ever 1000000:1 dynamic range image at these low frequencies, and the most sensitive upper limit on the elusive EoR signal yet obtained. In addition to these exciting science results, users also discussed ongoing work to improve the calibration and imaging capabilities of LOFAR. Updates on efforts to extend the LOFAR array were also presented by members of the French NenuFAR project, the Irish and Polish LOFAR consortia, and the KAIRA project. Its clear that LOFAR remains a growing and scientifically exciting instrument with an active scientific user community.

The final two days of the week were dedicated to a workshop focused on scientific exploitation of LOFARs first all-sky survey, the Multifrequency Snapshot Sky Survey (MSSS). Members of the MSSS team gathered together along with scientists from the wider community to discuss progress with the survey, plans for the release of survey data products, and of course getting good science out of these products. Details on the current processing for the survey were presented along with ideas and plans for improving the survey data products through future reprocessing. A first look at some of the potential science from MSSS was also presented by several of the MSSS science teams on a wide range of topics including giant radio galaxies, AGN and clusters of galaxies, transients and pulsars. The expected public data release of the first MSSS catalog and image mosaics is in early 2015 with a wide range of science papers soon to follow.

© Sandor Frey

For upcoming ASTRON/JIVE colloqiua, click here

© Astron

The instruments that are built come in all sizes. But while it is easy enough to be impressed with something the size of a steam locomotive, it takes a more discerning mind to appreciate a very small one. Those familiar with the Research and Development department will immediately recognize the hand of Albert van Duin, holding a very small board (2 mm x 2 mm) which he manufactured for our national Space Research organization (SRON) on a dedicated substrate.

Boards of such a small size can hardly be obtained from industry partners.

© public domain

For more details, see "The beginnings of radio astronomy in the Netherlands," by H. van Woerden and R.G. Strom, Journal of Astronomical History and Heritage, 9, 3-20 (2006).

Related images may be gleaned by clicking on "Archive" at the top of this webpage, and searching with the keyword "van de Hulst". Or, alternatively, by means of the following link.

© Ronald Halfwerk

The award is given each year to a woman who is unusually successful in the areas of mathematics, ICT, the natural sciences or technology, and who has contributed significantly to the mission of her employer through dedication, ideas and results. For those who know Gabby, her reaction was rather typical: "The chance of being nominated seemed very small to me, so the fact that I have won is an immense surprise".

Gabby has been employed as mechanical ingenieur by NOVA and ASTRON since 1997. She has played a key role in the development of the MIRI mid-IR imaging spectrometer for the ESA/NASA James Webb Space Telescope (JWST). By means of the clever use of symmetry she was able to advance and improve the design, production and testing of the instrument. In addition, she contributed to the development of many instruments for ESO's Very Large Telescope (VLT) in Chile. She currently leads the development of the mechanical part of the METIS instrument for the future European Extremely Large Telescope (ELT).

Gabby is more than a role model. She is an active member of the ASTRON/JIVE Diversity Committee, which, among other things, is involved in the discussion on gender equality in science & technology. Of course she participates in the yearly ASTRON/JIVE Girl's Day for secondary school students. This is part of the national VHTO Spiegelbeeld project, which aims to stimulate enthusiasm among girls and women for mathematics, the natural sciences and ICT. The next Girl's Day will be very soon, on thursday 24 April 2014.

© Kalliopi Dasyra (Observatoire de Paris)

© Madroon Community Consultants (MCC)

The people in this picture are just the tip of the iceberg. They do not even include the interviewer and the interviewee, who are cooped up in the darkness and silence of the ASTRON anechoic chamber. In addition, about ten other crew members were scattered in tense idleness in the corridor behind.

In this particular instance, Dr Albert-Jan Boonstra (visible on the monitor screen) was being interviewed about the multi-million DOME project by a team from IBM Zurich. At the same time, elsewhere in the building, another camera crew was interviewing the ASTRON chief astronomer about the vexing issue of "Freedom in Drenthe".

In short, just another day at the office in Dwingeloo.

© DESP / ASTRON

The subrack consists of two UniBoards, four ADUs (Analog to Digital conversion Unit) and a PAC (Power And Clock distribution) board. The system will be used for AAVS (Aperture Array Verification System) in the LFAA (Low Frequency Aperture Array) SKA consortium.

For this application, the WSRT/APERTIF beamforming firmware was re-used and modified to a beamformer for 16 antennas, with a bandwidth of 300MHz, on a single UniBoard.

© Hiddo Hanenburg

How nice it can be to go to work!

© ASTRON, 2014

After the multi-year development, procurement, production, integration and testing of the ALPHA-3 system, the hardware for the first two WSRT dishes (RT4 and RT5) was recently installed. Last Friday, fringes on an astronomical source were successfully measured. This is the first time at ASTRON (and, as far as we know, the second time in the world) that an interferometer consisting of dishes with Phased Array Feeds has been built. The fringes were measured instantaneously over the full 300 MHz bandwidth. All hardware was in place, i.e. the LNA, receiver, digital beamformer, clock distribution and correlator. After testing all subsystems individually, this result demonstrates that the integrated system, from LNA to correlator, is working.

The image shows the measured fringe for a single 781 kHz subband around 1400 MHz. For this experiment, two WSRT dishes on a 144 m E-W baseline were pointed at a strong astronomical source (Cas A) for a period of 300 seconds, without any delay tracking. Also shown is a measurement away from any strong source (i.e. pointing at the zenith), where the correlation should be negligible, or rather noise-like. The measured variance of the correlation coefficients is indeed as expected, i.e. 1/(Bt).

Until now, only single-dish measurements and correlations between an MFFE and a PAF have been performed. The present PAF interferometer allows us to characterize the APERTIF system at a deeper level. Specifications like bandpass stability and RFI immunity can now be validated with representative hardware and at the desired accuracy.

© Madroon Community Consultants (MCC)

It is a quaint but charming Dutch custom to spring such Royal Favour on the recipient as a total surprise. In this case, this was rather succesfull. Arnold was lured to the town hall under the false pretense of some meeting. The picture captures him at the moment when, just about to lose his temper over the poor arrangements, he suddenly notices a festive clutch of family and colleagues to his right.

Fortunately, he did not have a heart attack and, after a few moments of disorientation, he settled down to listen appreciatively to the well-chosen words of the Mayor of Assen. There were 5 recipients that day, covering a broad range of civic excellence. Since they were decorated in order of increasing rank, we were all very pleased when his turn came last.

After a stint at Naval Research, Arnold started his career at ASTRON (then called SRZM) in 1975. As an instrument scientist he made significant contributions to VLBI, and to the JCMT telescope on Hawaii. In 1987 he decided to try his hand at industry and rapidly rose to Director of Research at Ericsson. With the advent of the worldwide SKA process, he was lured back to ASTRON in 1995 to become head of the R&D lab, heading the development of new technology for the next generation of giant radio telescopes. He quickly became a champion of phased-array technology, which has become the heart of the European concept for SKA.

In addition to all this, he was very active on the wider plane of stimulating and organizing the development and application of science and technology, both locally and globally. This has culminated in his present job, for which he has been called back from retirement, to involve an entire continent (Africa) more closely in the grand adventure of radio astronomy. Such contributions to the wider community weigh heavily for the "Oranje Nassau".

It is clear that such a Cornucopia of activities cannot be managed alone, especially by someone who thinks as fast as Arnold. He is the first to recognize that he has been very lucky with his wife Els, who has kept no less than four houses warm for him while he was away on his many trips. He is also indebted to Truus van den Brink, his Office Manager, with whom he has formed an effective team for many years.

© NOVA Optical Infrared Instrumentation group

MATISSE is an instrument that is designed to coherently combine the light of up to four telescopes of ESO's Very Large Telescope Interferometer (VLTI). The combined light is imaged on a detector, to form an interference pattern from which a high-resolution image of the observed source can be reconstructed. In this way, the VLTI with MATISSE emulates the aperture of a telescope with a diameter of up to 200m, giving a spatial resolution up to 5 milli-arcsec in the 2.8-5 and 8-13 micrometer wavelength bands. The spectral resolution is between 30 and 5000.

With these characteristics, MATISSE is extremely well suited for the study of Young Stellar Objects (YSOs), extra-solar planets and Active galactic nuclei (AGNs), asymptotic giant branch stars (AGBs) and planetary nebulae.

The NOVA/ASTRON Optical Infrared instrumentation group is responsible for building the Cold Optics Benches (COB) for MATISSE. The first COB unit, which operates in the 8-13 micrometer N-band, is currently at MPIA/Heidelberg were it is tested at its cryogenic working temperature. Last month, for the first time, the Aquarius detector recorded light from a test laser source at its working wavelength, with two spectral lines around 10.5 micrometer.

The above image shows the interferometric fringe-patterns of the two laser lines. The cross-section of one is shown in the inset. The orange colour represents the thermal background. The white spots originate from the 10.5 micrometer test laser. The spatial direction is horizontal, and the dispersion direction is vertical. The two directions have different magnifications, in order to optimally match pixel size. The vertical bands on the left and right of the interferometric image contain photometric information for each telescope.

In this experiment, the interferometric image is formed by combining 3 telescope beams. The spacing of the fringes of the interference pattern depends on the separation of the beams in the pupil plane. Note that the clear diffraction rings of the photometric laser spots give a first indication of the image quality.

More information may be gleaned by clicking on "Archive" at the top of this webpage, and searching with the keyword "MATISSE". Or, alternatively, by means of the following link.

© Alice Harding (NASA/GSFC)

(For upcoming ASTRON/JIVE colloquia, see www.astron.nl/colloquia)

© ASTRON

We make use of commercial-of-the-shelf components and novel photonic integrated circuits (PICs) that are developed in collaboration with other R&D institutes and companies. We also offer an elaborate measurement setup, with which the electrical and optical characteristics of photonic ICs can be determined.

This spring, the Photonics Lab moved from a cramped room with an awkwardly placed pillar in the middle to a better location. This new room offers the possibility for working on several projects in parallel, while leaving space for the experimental work of visiting students.

Most of our photonic integrated circuits and RF/photonic systems have little or no shielding against interference signals (RFI) that originate from e.g. the ASTRON wireless network. To avoid any RFI-related disruption of our measurements, the walls of the lab are covered with a conducting mesh, and the windows with a special metallic foil.

Unfortunately, the excellent RFI reflection characteristics of the foil do not only shield for GHz frequencies. It also has good reflectivity in the visible spectrum, which makes it difficult to look in through the windows. Since we are very happy to show you what is happening inside, we are investigating how we can reduce this mirror effect. Until we have found a solution, the best way to see our work is to just come in: feel free to look around and ask some questions of the Photonics Team (Photoneers?): Klaas Dijkstra, Lesley Goudbeek and Peter Maat.

© Timothy Davis, NASA/ESA

In this talk I will describe these observations, and what they can tell us about the regeneration of red-sequence galaxies. I will show how kinematic misalignment measurements, gas-to-dust ratios and derivations of the gas phase metallicity, combined with simulations and models, can be used to put constraints on the origin of the cold ISM in these systems. It seems that in the field mergers and/or cold gas accretion dominate the gas supply, while in clusters internal secular processes become more important. Finally I will show that molecular gas is an excellent kinematic tracer, better than most others at tracing the underlying potential of galaxies. This provides a powerful tool for both studying the large scale mass and light distribution in galaxies (e.g. with the CO Tully Fisher relation), and probing dark objects lurking at the hearts of galaxies.

I will show using high-resolution interferometric observations that one can resolve molecular gas kinematics within the sphere of influence of local supermassive black-holes, and present the first ever black-hole mass measured in this manner.

© Madroon Community Consultants (MCC)

It is a quaint but charming Dutch custom to spring such Royal Favour on the recipient as a total surprise. In this case, this was rather succesfull. Arnold was lured to the town hall under the false pretense of some meeting. The picture captures him at the moment when, just about to lose his temper over the poor arrangements, he suddenly notices a festive clutch of family and colleagues to his right.

Fortunately, he did not have a heart attack and, after a few moments of disorientation, he settled down to listen appreciatively to the well-chosen words of the Mayor of Assen. There were 5 recipients that day, covering a broad range of civic excellence. Since they were decorated in order of increasing rank, we were all very pleased when his turn came last.

After a stint at Naval Research, Arnold started his career at ASTRON (then called SRZM) in 1975. As an instrument scientist he made significant contributions to VLBI, and to the JCMT telescope on Hawaii. In 1987 he decided to try his hand at industry and rapidly rose to Director of Research at Ericsson. With the advent of the worldwide SKA process, he was lured back to ASTRON in 1995 to become head of the R&D lab, heading the development of new technology for the next generation of giant radio telescopes. He quickly became a champion of phased-array technology, which now is the heart of the European concept for SKA.

In addition to all this, he was very active on the wider plane of stimulating and organizing the development and application of science and technology, both locally and globally. This has culminated in his present job, for which he has been called back from retirement, to involve an entire continent (Africa) more closely in the grand adventure of radio astronomy. Such contributions to the wider community weigh heavily for the "Oranje Nassau".

It is clear that such a Cornucopia of activities cannot be managed alone, especially by someone who thinks as fast as Arnold. He is the first to recognize that he has been very lucky with his wife Els, who has kept no less than four houses warm for him while he was away on his many trips. He is also indebted to Truus van den Brink, his Office Manager, with whom he has formed an effective team for many years.

© Astron

The National Committee 4 en 5 May and the province Drenthe set up the official program in the Nieuwe Kolk Theater in Assen. Mary Robinson, the first female president of Ireland and former High Commissioner for Human Rights will give the traditional 5 May speech this year. Also Prime Minister Rutte will address the audience of special guests. The Noord Nederlands Orkest and pop singer Ellen ten Damme will take care of the musical accents of this special ceremony

A short film on the theme of Freedom will be presented at the opening of the ceremony. The movie "follows" four people to present various views of freedom while highlighting important activities and other aspects of Drenthe. One of these is Raffaella Morganti, as astronomer of ASTRON. In this movie, ASTRON appears prominently with some nice shots of the building, the Dwingeloo telescope and of LOFAR (also taken using a drone). The movie will also be shown on national television.

A few weeks ago, a crew of four people have been filming at ASTRON/JIVE and at LOFAR. They had a lot of fun exploring and admiring the new building (including the view from the room of our director)!

© © Anne Archibald 2014

For most observations, one can use a standard technique called a polyphase filterbank to improve channel rejection at the cost of a small loss in time resolution - a kilohertz frequency resolution might require sixteen milliseconds of integration, rather than one. But when observing a millisecond pulsar, where one wants to see the sub-millisecond details of the pulse, these techniques are not sufficient.

A family of techniques, called cyclic spectroscopy, have been developed by mechanical and acoustic ingenieurs for precisely this kind of situation: instead of restricting the analysis to such a short time that the signal appears to be constant, the analysis is able to cope with the periodic modulation of the pulsar signal. One can therefore use very long integration times and obtain very high frequency resolution. Unfortunately, these techniques are rather new to pulsar astronomers, and so the implementation in the software package dspsr suffered from very bad spectral leakage: the black curve is the apparent spectrum due to some narrow-band interference. It has powerful ripples extending many kilohertz on both sides, ruining much of the band. The red curve shows the result of a newly-implemented technique that drastically reduces the spectral leakage, leaving the signal contained within a kilohertz or two, where it can easily be excised.

These data come from an observation of PSR B1937+21 observed with the Westerbork Synthesis Radio Telescope and the PuMaII backend. Although not shown here, the full profile of this 1.55-ms pulsar is resolved in spite of the 1.22-kHz spectral resolution.

© ASTRON

This complex picture highlights a diversity of ETG formation histories which may be lost in the relative simplicity of their inner structure and emerges when studying their outer regions. We find that hydrodynamical simulations have difficulties reproducing the HI properties of ETGs. The gas discs formed in simulations are either too massive or too small depending on the star formation feedback implementation. Kinematical misalignments match the observations only qualitatively. The main point of conflict is that nearly all simulated FRs and a large fraction of all simulated SRs host co-rotating HI. This establishes the HI properties of ETGs as a novel challenge to simulations.

A paper presenting these results is now accepted for publication in MnARS as part of the ATLS3D effort: Serra P., et al. [including Oosterloo & Morganti], 2014, http://adsabs.harvard.edu/abs/2014arXiv1401.3180S “The Atlas3D project - XXVI. HI discs in real and simulated fast and slow rotators”.

© NL SKA Office

The week started with the 1st MIDPREP workshop. It was followed by the first "all-hands" meeting of the SKA MFAA Consortium. Obviously, there was a considerable overlap in the participants of both meetings, most of whom are shown here. They also include representatives from the SKA Office in Manchester (UK).

MIDPREP is an EU funded FP7 program enabling the exchange of knowledge and staff between two leading European research institutes and three South African partners. MIDPREP builds and develops relevant research networks through exchange of experienced and early-stage radio scientists and engineers between South Africa, Sweden and the Netherlands. Through that, MIDPREP aims at a common view on design-related aspects for radio telescopes, and to advance radio-optics, calibration, ICT, processing and technology views and (possibly "green") designs of SKA-mid. Knowledge gained by the MIDPREP project will be disseminated among a larger community by means of annual workshops, of which this one in Dwingeloo was the first.

Like all eleven SKA consortia, the MFAA Consortium has a wider membership, with participants from institutes and companies all over the world. It is special in the sense that it is the only consortium that has no part in the first phase of SKA, and thus operates on a slightly different time-scale.

During the week, participants were treated to unusually clement spring weather, as this picture taken at ASTRON's sun-deck shows. In the evening the group enjoyed a traditional Dutch pancake dinner at the nearby Bospub.