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A daily view of all the goings-on at ASTRON and JIVE.

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  • 02/28/16--16:00: SKALA2 antenna assembly
  • © ASTRON

    Deploying 131072 antennas at the Murchison Radio-astronomy Observatory (MRO) in Western Australia, will be one of the interesting challenges of SKA1_LOW.

    One of the goals of the LFAA Aperture Array Verification System (AAVS1) is to demonstrate the required assembly and deployment schedule. It will also provide feedback for the design, which can then be further optimized towards future improvement on these subjects.

    We're pretty confident that we are on the right track, as it takes an unskilled person under five minutes(*) to completely assemble and deploy a single antenna. One of the items to assist us is the assembly-jig, which can be seen at bottom-left.

    The orange cable feeding the antenna top-part houses both the fibre-optic cable to transport the RF signal (using RFoF) and a copper wire to feed the FrontEnd electronics. This hybrid cable will be connected to the Antenna Processing Interface Unit (APIU), which will be a single box situated in the middle of each SKA_Low station.

    (*) Editor's note: This adds up to about 10.000 hrs for 130.000 antennas, or 200 hrs per person for a team of 50. A nice summer-student project to give the next generation of radio astronomers that hands-on feeling and sense of co-ownership.

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  • 02/29/16--16:00: What's going on here?
  • © Copyright ASTRON

    When I passed the ASTRON Reading Room, my eye caught a gathering of this illustrious group. Jan Noordam, Wim Brouw, Jaap Bregman, Arnold van Ardenne, Johan Hamaker, Thijs van der Hulst and Ger de Bruyn are clearly up to something, but we are not allowed to know. Hopefully these giants from radio astronomy will surprise us in the coming months.

    Editor's note: Well spotted by our young colleague. This inconspicuous group, a.k.a. "De Stille Kracht", is indeed up to something. They are united in their great good fortune of having been involved in an altogether unusual success story: The Westerbork Syhthesis Radio Telescope(*). Led by Mr WSRT, they are engaged in preparing a brief history of the last 45 years, to share with you all.

    (*) For more than a decade, the WSRT was the most powerful astronomical telescope in the world, operating in the most exciting wavelength area (most of the Nobel prizes awarded to astronomical subjects were based on radio observations). And even after other radio telescopes caught up, the WSRT continued to set the standard for instrumental excellence for several more decades. The success was magnified by the absence, in the 70's and early 80's, of competition from satellites or mountain top telescopes. Ah, it was good to be alive. (It still is, of course.)

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  • 03/01/16--16:00: Ready to shoot...
  • © Rik ter Horst

    This is the very first image taken with my new 400 mm F/3 Dobson telescope (with its thin meniscus mirror). It shows the Moon which is partly lit directly by the Sun, and partly (dark side) by Sun-light that is reflected by the Earth.

    A short exposure (1/125 sec) was used for the bright crescent, and a longer one (1/10 sec) to catch more detail in the shadow side. The two images were then combined with Photoshop, resulting in this 'HDR'-image. However, the visual appearance was even more impressive.

    Watch this space.

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    © Paul Demorest

    Millisecond spin-period radio pulsars provide us with unique astronomical "laboratories" for exploring fundamental physics in a variety of ways -- from the physics of matter at super-nuclear density, to experimental tests of gravity. They have also provided the only experimental evidence so far for the existence of gravitational waves (GW).

    A set of millisecond pulsars acting as precise astronomical clocks may also be used as a direct GW detector, sensitive to the nanohertz-frequency GW expected to be emitted by supermassive black hole binary systems.

    The NANOGrav project has been monitoring a set of pulsars using the Green Bank and Arecibo radio telescopes for the past decade; I will present an overview of the project, current results from NANOGrav's recent "nine year" data release, preview the upcoming "eleven year" data set and summarize prospects for future GW detection using pulsar timing.

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    © ASTRON

    At the 23rd and 24th of February 2016 the dPDR was held for the CSP (Central Signal Processor) Low.CBF (Low Correlator and Beam Former) system in SKA (Square Kilometre Array). The following documents were tabled for the dPDR:

  • detailled design document

  • prototyping plan

  • requirements document

    The review panel requested a number of presentations to be given during the review about the system, signal processing, power, cooling and traceability of requirements. Furthermore the major issues from the Observation Action Register (OAR) have been discussed.

    The Low.CBF team (ASTRON, CSIRO and NZA) has put a lot of effort into the delta PDR preparations, working under severe time constraints. However the hard work of the recently formed team (about half a year ago) was rewarded with success. Unfortunately, we cannot enjoy this moment for too long, and take a well-deserved rest, since we have to ramp up our efforts again to achieve our next internal milestone towards the Critical Design Review (CDR).

    The photo shows the panel members and part of the Low.CBF team participating in the review. They include former colleagues Grant Hampson (now at CSIRO) and Andre van Es (now at SKA Office).

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    © ASTRON

    Sometimes, if you want to test your ideas, the best way is to grab your prototype, hook it up to some measurement equipment, and tap it with your hand.

    In this case, we were testing what would be the best option to mechanically connect our antennas together. We like to have some flexibility in this connection to allow for production tolerances and material deformation due to temperature changes. However, it must remain sturdy enough to retain a good electrical connection.

    We verified this by measuring the transfer function between two antenna elements. We tried different methods of connecting these two elements together and verified what influence movement and vibrations had on the transfer function. The ideas which have survived this basic test are now being developed further and will of course be subjected to more "scientific" testing.

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    © Zsolt Paragi

    Prof Imke de Pater (Berkeley) will be paying us regular visits this year, in the context of ASTRON's Helena KluyverFemale Visitor Programme(*).

    Among other things, she is taking this opportunity to reduce a unique set of simultaneous observations (in 2013) of Jupiter with the WSRT (MFFE, 6, 21, 35 and 92cm) and LOFAR (LBA and HBA). This will produce an unusually wide spectrum (50-5000 MHz) that can be used to test new (and old) radiation models of our ruling planet. The polarization information will help to separate Jupiter's thermal (atmospheric) and non-thermal (magnetosphere) emissions.

    Imke was the first to image Jupiter's radio emission with the WSRT, as part of her Leiden thesis in the late 70's. Since Jupiter moves w.r.t. the background sky, and rapidly rotates around its axis, this challenged the WSRT observation and data reduction systems considerably. After this success, she has been studying Solar System objects ever since (Her own model of Jupiter's radio emission has stood for 20 years). She recently served as department chair in Berkeley.

    The picture shows her reducing the WSRT data, assisted by Richard Strom and Ger de Bruyn. The latter is wielding the rapier of NEWSTAR, still the ablest data reduction system for WSRT data (until APERTIF comes along, of course). The associated LOFAR data is being reduced by Julien Girard (Paris).

    Imke will be back in Dwingeloo in May, hopefully accompanied by her long-time significant other Wil van Breugel. The latter has also used the WSRT extensively in the past, but always refused to visit the instrument itself, for largely superstitious reasons.

    (*) For more information about the Helena Kluyver Female Visitor programme:

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  • 03/08/16--16:00: APERTIF-6 Software ready
  • © R.H. van den Brink / M. Loose

    In February 2016, the APERTIF software team met a very nice milestone. The first part of the APERTIF software was finished. This APERTIF-6 software is needed to control the instrument. System Services (ie Message Bus) and Monitoring & Control (drivers and controllers) are present. With this part of the software, the Technical Commissioning and the Early Science Commissioning can be undertaken.

    Marcel Loose gave a nice lunchtalk on Feb 25th, which still can be viewed by ASTRON personnel through this link.

    The second part of APERTIF software development (APERTIF-12 Software) will be focused on user-oriented software (Task specification, Data Inspection, Archiving). The final scientific data reduction is the responsibility of the users themselves.

    The team did a marvelous job in making this delivery with only 2,5 FTE divided over 6 persons. Apart from the fact that our team is very capable, and has a lot of knowhow, the use of the new Agile/Scrum way of working seems to be fruitful as well.

    There is no doubt that the team (Alexander van Amesfoort, Arthur Coolen, Ger van Diepen, Marcel Loose, Pieter Donker and Ruud Overeem, with support from Teun Grit) will deliver the APERTIF-12 software equally successfully.

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    © Wim Ubachs (Amsterdam)

    An overview is presented of quasar absorption methods to search for a possible variation of the proton-electron mass ratio mu=m_p/m_e on a cosmological time scale. Details of the analysis of astronomical spectra of molecular hydrogen and carbon monoxide, obtained in the optical regime with large 8--10 m class telescopes, equipped with high-resolution echelle grating based spectrographs, are explained. Another method is that of radio astronomy, where specifically methanol molecules are the target of interest in view of their sensitivity to the varying constant.

    Theoretical physics scenarios delivering a rationale for a varying mu will be discussed. Also a recent approach to detect a dependence of the proton-to-electron mass ratio on environmental conditions, such as the presence of strong gravitational fields, will be highlighted. For a recent review: W. Ubachs et al., arXiv:1511.04476

    Displayed is the ESO Very Large Telescope at Paranal (left) and the laser system at LaserlaB Amsterdam. Both instruments are used to investigate the spectrum of molecular hydrogen, either at high redshift in the Early Universe, or at zero redshift in the present epoch. Comparison between the result will provide insight in the constancy of fundamental constants.

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    © ASTRON

    Harvey Butcher came to visit on 22 February. He was ASTRON's Algemeen Directeur from 1991 to 2007, and thereafter has been living in Australia.

    "I had heard the EU keeps giving ASTRON money," he remarked, "and I was keen to see how things have progressed in the interim, particularly in the lab. I must say, I was most impressed! You guys really are head and shoulders above the competition. Keep up the good work!"

    Gert Kruithof showed him the latest developments in the lab. Mike Garrett filled him in on the scientific programme, the financial situation, and the changes at NWO that his successor will have to deal with. And Michiel van Haarlem told about trying to get a new international organization set up to carry the SKA forward.

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    © Rik er Horst

    Sunday evening, time to go to bed. BLIPP! A message from 'Solaris', an app monitoring the sun and Auroral activity. The KP index was 6, which means that it might be possible to observe the Aurora Borealis from my location (Beilen, the Netherlands)!

    Despite clouds I tried to look for a glimpse and yes! there was a faint reddish glow visible in the North through the holes in the clouds. I grabbed my camera and made a series of images. About 18 of these images were used to create the animation above. Luckily, the clouds were kind to me and made some room for this beautiful event.

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    © ASTRON

    Today and tomorrow, ASTRON will host and organise a Dutch national SETI (Search for Extraterrestrial Intelligence) meeting at our HQ in Dwingeloo. The main goal is to bring together for the first time, researchers in the Netherlands actively working in the field and other closely related areas.

    The meeting will include presentations that cover a broad range of relevant topics that will be organised along the following lines:

    - Radio SETI searches and Breakthrough Listen,

    - SETI searches at other wavelengths, incl. optical and infrared,

    - SETI and its impact on human culture e.g. art, message composition,

    - Cosmic Transients,

    - Artefact SETI (e.g. signatures of mega-structures, Dyson spheres, etc),

    - Technology challenges for next generation SETI research,

    - Exoplanets & bio-signatures,

    - Messaging to Extraterrestrial Intelligence (METI).

    The meeting will finish off with Dr. Andrew Siemion (Director of the Berkeley SETI Research Center and PI of Breakthrough Listen) giving this week's ASTRON JIVE colloquium (N.B. this week on a Wednesday at 15.30!).

    We expect about 30 external participants to attend. The meeting will be held in the van de Hulst auditorium - there should be ample space for ASTRON and JIVE staff to also attend those parts of the programme of special interest.

    The programme is now available at:

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    © Andrew Siemion

    Andrew Siemion is today's Colloquium speaker. Andrew's presentation will round off this week's Dutch National SETI meeting. The topic is likely to be of wide interest to ASTRON & JIVE staff.

    Abstract: Nearly 14 billion years ago, our universe was born in a spectacular and dynamic event known as the "big bang". After several hundred million years, the first stars lit up the cosmos, and many hundreds of millions of years later, the remnants of countless stellar explosions coalesced into the first planetary systems. Somehow, through a process still not understood, the laws of physics guiding the unfolding of our universe gave rise to self-replicating organisms - life. Yet more perplexing, this life eventually evolved a capacity to know its universe, to study it, and to question its own existence. Did this happen many times? If it did, how? If it didn't, why not?

    For millennia, humanity has pondered their place in the cosmos and asked the question "Are we alone?". For the first time in our history, the answer may be within our grasp. Astronomers have recently determined that the key environmental factors that are believed to have given rise to life on Earth are present in abundance throughout the Milky Way galaxy. Long lived stars, planets, water and complex organic molecules are now known to be ubiquitous. Armed with the certainty that life could have developed elsewhere, scientists everywhere are racing to determine if indeed it did, and if so, whether some of that life went on to develop a technological capability similar to our own. In July 2015, Yuri Milner and Stephen Hawking announced Breakthrough Listen - a 10-year 100-million-dollar search for extraterrestrial intelligence. This program will be the most sensitive, intensive and comprehensive search for intelligent life beyond the Earth in the history of humanity.

    I will discuss the scientific rationale behind the search for extraterrestrial intelligence and some of the recent discoveries in astrophysics that are informing and spurring the search. I will also review the Breakthrough Listen Initiative, including the current observational status, early results and plans for the future.

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    © ASTRON

    On 2-4 March, a SKA delegation visited ASTRON to learn about LOFAR operations. The delegation involved representative members of the SKA TM consortium, which is responsible for the analysis and the design of the user interfaces (observations management and telescope management) for the SKA telescope.

    The visiting group (A.Marassi, G. Brajnik, V. Alberti, and M. Nicol) were given an extensive overview on LOFAR alarm handling systems, LOFAR user interfaces, architecture, implementation, and technologies. Various people from the different Radio Observatory departments had the chance to meet with the SKA delegation and contributed to give a complete overview of LOFAR operations from a very broad perspective. Obviously, the LOFAR experience will be very important for the definition of the future SKA operations.

    The photo taken in the LOFAR control room shows the visitors and part of the ASTRON people involved in the review.

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  • 03/17/16--17:00: A LOFAR project for Dan
  • © ASTRON

    On the 6th of December last year, many of us received the sad news of the passing of Dan Harris. The life and career of Dan has followed the development of radio technology and the improvement of radio telescopes. He was there when the Northern Cross was built in Italy and he was here, in the Netherlands, in the highly productive first decade of the WSRT, as one of the first users of this instrument.

    The study of radio sources and radio jets has been the "leitmotif " of Dan's research. He used the powerful combination of radio and X-ray observations to unveil many of the complicated aspects of the physics of radio jets. Dan has been always aware of this “power” and, in particular, he was aware that things would even be better by extending the radio data to the lowest possible frequencies.

    Perhaps counter-intuitively, the low-energy electrons which emit at low radio frequencies are key for understanding the processes driving the X-ray emission. These low-energy electrons are also long-lived (hundreds of thousands of years), and over this timescale they not only encode the history of the radio source, but also produce inverse Compton scattering with cosmic microwave background (CMB) photons and originate X-ray emission.

    Thus, it was not surprising to see Dan's great interest for the LOFAR radio telescope! Dan was interested in LOFAR from the early stages and, actually, even before the start of operations. Dan's idea was to use LOFAR to resolve the debate about the dominant emission mechanism for the X-ray emission of powerful radio jets. The low radio frequencies covered by LOFAR would tell us whether the X-ray emission from radio jets is the extrapolation of Inverse Compton/CMB models or not. But to be able to answer this question, the high spatial resolution of International LOFAR was required. Therefore, he has been anxiously waiting for the long-baseline capabilities of LOFAR, asking about the status and the progress in the calibration and imaging at every occasion I would meet him. Only with an International LOFAR observation one could match the resolution at higher frequencies and resolve the jet structure: no other low-frequency radio telescope could provide this!

    The pilot study we proposed was targeting one of Dan's favourite objects, 4C19.44. This object has a bright jet with knots observed both in radio and X-ray. With the help of some of the LOFAR long-baseline experts at ASTRON (Javier Moldon, Adam Deller and Raymond Oonk) an impressive sub-arcsecond image was obtained at 150 MHz, using 8 international stations in combination with the Dutch array (picture on the left). The great quality of the image is even more evident when compared with the high-frequency VLA image; see the overlay on the right between the high-frequency (4.8 GHz) VLA image and the LOFAR one.

    This perfect coincidence between the structures was exactly what Dan needed for his experiment; he was delighted to see this result.

    Unfortunately he did not have the time to complete the full analysis of these data, but we have made a commitment to complete the 4C19.44 long-baseline paper; both for his memory and because of the lot of work he has dedicated to this project. This is what he would have liked to see! Hopefully, we will also be able to expand this pilot project to more objects, as Dan was planning to do.

    A Memorial for Dan Harris is held in Boston on Saturday 19th March and we hope this short contribution will complete the picture of Dan's active scientific life until the last day, as we would have expected from him!

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    © ASTRON

    In the evening of March 7th 2016, there was an unannounced and alarming event at the premises of ASTRON in Dwingeloo. The Emergency Response Team ("BedrijfsHulpVerlening, BHV for short) had organized a fire-fighting exercise in cooperation with the local fire brigade. According to the scenario, a smoke detector in the laundry room of the guesthouse was supposed to go off in the early evening.

    However, two hours before this planned exercise, the BHV-team was surprised by an additional fire alarm. Shortly after closing time of the reception desk, the slow-whoop alarm sounded. The BHV responded immediately, and all employees and guests left the building in good order, to gather at the assembly point (Verzamelplaats).

    The BHV team members were then confronted with what they believed was a real fire in the building. When the problem was located, the BHV took all the necessary measures to rescue the victim, in this case a dummy (see picture 2). Because this emergency took place at a time when the reception was closed, the BHV not only had to deal with the unexpected situation, but also had to take care of tasks that the receptionist normally performs.

    This unexpected extra evacuation drill did of course not cancel the originally planned exercise. At 7:15 PM, a smoke detection fire alarm in the guesthouse was received by the Dwingeloo fire brigade. All guests and employees left the building.

    Since, according to the original scenario, the BHV was not supposed to be in the building this evening, the team was ordered to wait for the fire brigade to arrive. The latter had to find their own way to the fire location, and to gain access to the guesthouse. Since a large tree had somehow fallen across the access road to ASTRON, it took some extra time for them to deal with this (see picture 3). Then the BHV-members had to take care of their own problems, as they were told that a technical engineer was still in the building, who had not responded to the fire alarm. This person had to be found, and quickly!

    After a thorough search of the building, the engineer was found in a small service room, which can only be accessed via a ladder. Unfortunately he was too seriously injured to climb down the ladder himself, so we had to ask the fire-fighters for help (see picture 4). With their skill and equipment, they were able to take control of the situation at the guesthouse (see picture 5). The signal "brand meester" was given at half past nine in the evening.

    Afterwards we evaluated the exercise together with the fire fighters (see picture 6). The two successive drills were exciting and exhausting, but full of new elements from which the BHV and the fire fighters could learn. Special thanks to all the volunteers, fire fighters, victims and evacuees.

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  • 03/21/16--17:00: The sunny face of ASTRON
  • © Madroon Community Consultants (MCC)

    Uncanny, what? The same radiant smile, and the same fashion choices. And when confronted with the camera, they both assumed the same attitude, without even breaking parity.

    For once, your humble editor was silenced by the myriad possibilities for a blurb underneath this picture. I will just say that the smiles are for real.

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  • 03/22/16--17:00: How they see us

    The confluence of many disciplines is required to develop digital systems for radio astronomy. For some of these disciplines, we work closely with industry. Such collaborations offer us the opportunity to gain knowledge of the latest possibilities in the production of PCB assemblies, and housing solutions for our boards. On the other hand, they also push the companies to unexplored limits. Two recent articles written by Neways Leeuwarden and Koning & Hartman describe such stimulating collaborations from their perspective.

  • The interview (in Dutch) with Mohammed Alhillawie of Neways shows how we work together to achieve the latest assembly possibilities for the production of the ASTRON/JIVE UniBoard2. We have been working with Mohammed for an extended period, which enables both sides to push the limits of design, while maintaining a producible board.

  • In the article (in Dutch) by Koning & Hartman the design and production of the UniBoard subrack for the WSRT/Apertif system is described. The article gives a nice view of our Sjouke Zwier working with their John Vink to develop the housing for Apertif.

    P.S. Sometimes, a look from the outside reminds us how fortunate we are to be building instruments for gaining knowledge about the Universe!

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    © Bjorn Emonts

    There is a growing notion that the formation of massive galaxies must be a two-phase process, with a late phase that is dominated by galaxy mergers and an early phase that is driven by cold gas accretion.

    I will present observational evidence for large (~100 kpc) reservoirs of very cold molecular gas in the halo-environments of proto-cluster radio-galaxies at z~2. We discovered that this cold molecular medium is related to a variety of important evolutionary processes, from cold gas accretion to jet-induced feedback and galaxy merging. These processes reveal the important role of the cold molecular inter-galactic medium (IGM) in the early formation of massive galaxies.

    I will also show that studying the molecular IGM is only possible with radio interferometers that are sensitive to detecting low-surface-brightness emission of widespread cold gas. In this respect, I will explain how traditional "cm" instruments like the ATCA and VLA (which also operate in the 30-50 GHz regime) form a crucial complement to ALMA, and how technical considerations regarding surface-brightness sensitivity can optimise future radio interferometers for studying the cold molecular medium.

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    © HvdL

    We have lost dr. Roel Gathier, managing director of ASTRON's sister institute SRON, manager and leader in the Dutch astronomy community, specifically in space research, gifted communicator. Roel is survived by his wife Wilma, his adult children Celine, Wouter and Anouk and his brothers Henk and Bas. They all spoke movingly and with depths of feeling at the memorial meeting in Leiden on March 18th. Roel's death is a devastating reality.

    Roel became a public figure early in his career. A TELEAC television course consisting of thirteen public TV hours, telecast twice each week in 1980, and repeated in 1981 under the title Moderne Sterrenkunde (Modern Astronomy) was designed and directed by HvdL. He engaged two senior astronomy students for the two major roles in this enterprise: Niek de Kort from Leiden Observatory and Roel Gathier from Amsterdam's Pannekoek Institute. The three of us worked together intensely, advised by a TELEAC team of television professionals.

    Niek wrote the course book, chapter after extensive chapter, and Roel wrote the corresponding TV script based on Niek's chapters. Harry edited both and involved one prominent expert from the Dutch astronomy community on the subject of each lesson. This production method assured up-to-date quality. Crucial in the series' remarkable success was Roel's presentation talent (see the picture), his unassuming, yet sparkling approach, his friendly, encouraging manner of introducing difficult materials and concepts. According to the official kijkcijfers (ratings) we reached a quarter of a million people and sold all of the 33 000 copies of Niek's splendid 450 page book. The registration for first year astronomy shot upward, and many a Dutch astronomy professional today originates from the course.

    Roel became a Bekende Nederlander, and that aura never left him. After completing his Masters and PhD in Astronomy at Utrecht and Groningen respectively, Roel's first job was as a civil servant at the Ministry of Onderwijs en Wetenschappen (MinO&W) with special responsibility for relations with governmental and intergovernmental organizations. He was instrumental in helping Richard Schilizzi and other VLBI astronomers, in securing a major Dutch contribution to the EVN correlator at JIVE, Dwingeloo. Roel also organised and brokered various key events, including the meeting in Den Haag in which the Netherlands, France, Sweden and the UK agreed to establish JIVE.

    The pinnacle of his impressive career is his chairmanship of ESA's Science Program Committee (SPC), Europe's foremost policy unit in space science. His much too early passing is a blow to the SPC, to SRON, to our astronomy and space science community at large, and to his innumerable friends.

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