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

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    © WNB

    On thursday/friday 6/7 July 2017, ASTRON and the astronomy department of Groningen University will organise WimSym77, a 2-day symposium to honour the many contributions of Wim Brouw to radio astronomy, especially in the context of the highly succesful Westerbork Synthesis Radio Telescope (WSRT).

    Wim started his SRZM/NFRA/ASTRON career by saving the WSRT, i.e. by almost singlehandedly writing the observation, calibration and imaging software. This task had been a little underestimated in the plans because the WSRT was the first telescope in which computers played a central role. To do this, he had to advance the theory of Aperture Synthesis, especially for East-West arrays. Very importantly, he completed it all on time for the Royal Opening in 1970! His software was the basis for all the great WSRT discoveries of the 1970's.

    He then played a significant role in producing the famous ultra-high dynamic-range WSRT images, by re-implementing the existing Redundancy (selfcal) package into its more user-friendly NEWSTAR guise. For good measure, he included extra functionality, like mosaicking for the WENSS survey. Finally, he wrote several modules for AIPS++ that are still widely used today, e.g. by CASA, BBS and MeqTrees. In his spare time, he squeezed unlikely performance out of the computers of the day, and he wrote a suite of financial administration software for ASTRON.

    Apart from being a highly talented, and unbelievably productive scientific programmer, Wim was also a born "bestuurder". He served for almost 20 years as the effective Director in Dwingeloo. His job was complicated by the organizational structure at the time, which included a rotating chairmanship of the "Werkgroep" in Dwingeloo. Wim�s defining characteristic as a Leader was that he hated to give direct orders, hoping that others would see the way forward as clearly as he did, and quietly doing things himself if they didn't.

    Judging by the Alliant machine in the background, the above picture was taken around 1985, in the old Computer Room. Wim very much looks the part of the director/prodigy, much more so than he did in real life. After a decade in Australia, we are happy to have him back in the Netherlands as a general-purpose sage.

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    © G. van Diepen, J. Morawietz (not to be spread via Social Media!)

    Tuesday evening April 4th the PV organised an evening with two lectures for non-technical people.

    Andre Gunst talked about "How do they do it: the radio telescope seen as a factory". Inspired by the Discovery program "How do they do it" he explained in a simple way how the LOFAR telescope works by seeing it as a factory. A factory where at one side the noisy radiation coming from the sky is fed in as raw material and where at the other side astronomical images are delivered as end product. With the help of two volunteers acting as antennae, he showed very vividly how signals are delayed to synchronize them. Besides LOFAR, he briefly discussed other factories being built, such as Apertif and SKA.

    Joeri van Leeuwen talked about "The mysterious fast radio bursts". In 2007 astronomers found an extremely short and bright flash with the Parkes radio telescope. It appeared it had to come from about 4 billion lightyears away, thus very far and very long ago. Joeri discussed phenomena such as supernovae, pulsars, neutron stars, black holes, etc. People could 'hear' the Crab Nebula pulsar by letting the computer translate its pulses into sound. It is unknown what causes the extremely energy rich fast radio bursts of which 20 have been found so far. With the wide field of view of the new Westerbork Apertif receivers, astronomers hope to find many more such bursts and to determine their exact location.

    Prior to the lectures people could enjoy a Chinese buffet and drinks.

    About 65 people attended the lectures, of which 10 retired ASTRON employees and about 30 relatives (spouses, children, parents) of ASTRON employees. The people were very enthusiastic about the talks, so it is clearly an event to be repeated.

    The slides of the talks can be seen on the PV web page ( and one can contact Andre or Joeri for more details.

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    © Unkown

    Approximately one month ago CAMRAS received an e-mail from a woman charged with the conclusion of an inheritance. She found glass plate negatives in the house of a deceased lady. The box with the negatives contained a short note with the text 'For Dwingeloo?'. The woman charged with the conclusion asked if these negatives are interesting for CAMRAS. Because we were curious we said of course that they are interesting.

    A few days later a very well packed box arrived. They contained ten glass plate negatives. We were very surprised. The pictures on the negatives were taken during the hoisting of the dish of the Dwingeloo radio telescope on its tower. Albert van Duin made excellent scans of these negatives. The result is visible on this daily image (unfortunately not at full resolution). On one of the photographs professor Minnaert and Van de Hulst can be recognized. Thanks to the Dutch Royal Library who digitized approximately 60 million pages of old Dutch newspapers and made them accessible via the internet, we found that the hoisting of the dish happened on June 1st 1955. An article describing this event can be found at .

    The movie about the construction of the Dwingeloo radiotelescope made by Herman Kleibrink also shows the hoisting of the dish. This movie can be viewed via . (The movie will start at the point where the hoisting starts. You can of course watch the whole movie.)

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    © Lesley Goudbeek, Jan Idserda, Sjouke Kuindersma, Paula Fusiara

    At ASTRON we develop and create very specific and specialized products to make astronomy happen. At the R&D photonics group we develop RF over Fiber (RFoF). Our astronomy colleagues in Australia took notice of the RFoF technology and want to use it in their telescope upgrade. They requested 256 optical transmitter and receiver units, 512 modules total. This was a great opportunity for us to develop methods for producing these RFoF units on larger scale. And specialized products require specialized tool.

    To produce the 512 modules, pins of lasers and detector components had to be bent and cut a certain to be suited for assembly. This would have been a very labour intensive task to do by hand and the tolerances of the bends would be operator dependent. The mechanical department developed a bending tool that preform this task in mere seconds. The laser or detector component is placed in the tool and by a 3 stage press mechanism the tool does the following in one operation:

    - it secures the component tightly (front black element),

    - it bends the pins (the brass element),

    - it cuts the pins.

    Do note the very small dimensions off the components and assembly jig! Thanks to this tool we managed to prepare the components for assembly in mere hours instead of day's of intensive manual labour. Furthermore the tool can be used in the future to prepare plenty of more components!

    Special thanks to Jan Idserda, Sjouke Kuindersma and Paula Fusiara at the mechanical department for creating always awesome products.

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    © Victoria Grinberg

    We are made of stardust or, at least in significant parts, of material processed in stars. Hot, massive giant stars can drive the chemical evolution of galaxies and trigger and quench star formation through their strong winds and their final demise as supernovae. Yet, optical and X-ray measurements of the wind mass loss strongly disagree and can only be reconciled if the winds are highly structured, with colder, dense clumps embedded in a tenuous hot gas. But in (quasi-)single stars wind properties are inferred for the whole clump ensemble.

    No measurements of individual clumps or clump groups are possible. Luckily, nature provides us with perfect laboratories to study clumpy winds: high mass X-ray binaries (HMXBs), systems where a neutron star or a black hole accretes matter from the wind of a giant stellar companion and emits the so freed energy mainly in the X-ray band. This radiation is quasi-pointlike and effectively X-rays the wind, in particular the clumps crossing the line of sight towards the neutron star or black hole.

    I will show how we can use a variety of observations of the two of the brightest high mass X-ray binaries, Cyg X-1 and Vela X-1 to constrain wind properties.

    In particular, the long-term changes in absorption seen with RXTE reveal the dynamics of clump movements as well as wind porosity while the high resolution spectra obtained with Chandra-HETG and XMM-RGS hint on the layered temperature profile and comet-like structure of individual clumps.

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    © JIVE

    In April/May this year a two-week radio astronomy training school was held at the Ghana Radio Astronomical Observatory (GRAO) in Kuntunse, Ghana. The Kuntunse radio telescope is a 32m ex-Intelsat Satellite Communication Earth Station that has recently been converted for astronomical use. It is currently undergoing final testing by a commissioning team, which consists of the first Astronomy graduates from Ghanaian universities, together with staff from the South African Hartebeesthoek Radio Astronomy Observatory (HartRAO).

    This conversion is part of a larger project intended to build both skills and institutional capacity in SKA partner countries in preparation for the SKA, as well as to provide a scientific instrument in its own right: the African VLBI Network (AVN). JIVE is involved on several levels: the JUMPING JIVE EC project includes funding for developing the AVN and ensuring its inclusion in the EVN. Consequently, the GRAO has already participated in a fringe test with other EVN stations.

    This particular two-week training program was part of a joint effort by JIVE, HartRAO and the University of Manchester DARA (Development in Africa with Radio Astronomy) project to train local students in the (mystical) art of radio astronomy, with a special focus on VLBI. Jay Blanchard from JIVE leant a helping hand on the training programme, giving him a great opportunity to see the progress being made at the telescope, and meet some of the people who have been working with JIVE on fringe finding attempts. Of course, it was also an excellent way to get an introduction to local cuisine (fufu is amazing)!

    The students involved in this project (pictured above) will likely be the first operators and users of the AVN. It was encouraging to see the enthusiasm from these future AVN operators and users for getting their first real radio data!

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  • 05/21/17--17:00: BALTICS LOFAR training
  • © Astron

    In April, two Latvian VIRAC engineers Marcis Bleiders and Marcis Donerblicks started with a four-week LOFAR training. After a general introduction we went to Amsterdam for a two-day ILT face-to-face meeting. They met other station-owners and listened to their experiences with operating a LOFAR station, and doing science with it.

    The second week we payed a maintenance visit to Norderstedt station DE609. Hamburg engineer Nils Boehmer was our host and served good coffee in his mobile home. As can be seen from the pictures, they also did a RFI monitoring campaign. The measurement was repeated at the LOFAR core and will also be executed at the prospective LOFAR site Irbene in Letvia.

    The final two weeks they spent on the HBA-PC. The hardware and software were developed by three students of the Hanzehogeschool Groningen. Marcis and Marcis implemented a full beam-steering code for an HBA analog tile, and also created a read-back function for all sixteen HBA-FE element delay settings.

    They enjoyed the training and we look forward to seeing them back in the future. Thanks guys, for the fruitful engineering staff exchange.

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    On May 14, 2017 a supernova was detected in NGC 6946, also dubbed "The Fireworks Galaxy", by P. Wiggins from Utah. This was the 10th supernova that was detected in this galaxy since the first one was found in 1917. So it certainly earns its nickname.

    Beilen observatory had to wait for almost a week for favourable weather before the supernova could be imaged. The telescope is fully controlled by ACP Scheduler now, software that uses a database with targets to plan observations. As soon as the weather is safe at night (dark, clear, dry and not too much wind), the roof of the observatory opens automatically and the most favourably placed object is chosen from the database by the scheduler. For each object you can enter all kinds of constraints, like Moon phase, Moon distance from the object, minimum elevation, etc.

    The image on the right was made in the early morning of May 21, 2017 and consists of 6 x 600s integrations for Luminance, and 3 x 600s each for R, G and B. The supernova is on the top right, indicated by a red marker. On the left is the comparison image made on September 5, 2013 under much more favourable seeing conditions.

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    © Photographs by Rik ter Horst

    Words are not enough, to describe this beautiful piece of milling art. What we see here is the mechanical interface on which one of the four fibre-populated slit-heads will be positioned.

    A slit-head holds 609 to 960 optical fibres, each of which is placed at a particular position in the focal plane of the telescope, to collect the light from a particular celestial object like a star or a galaxy. It then accurately guides the light from these fibres into the WEAVE multi-object spectrograph.

    Back to the piece of art: what strikes us are the sharp edges, located in deep pockets, the smooth machined planes and neatly chamfered edges. The part provides stiffness (and thus position accuracy) to the slit-head, and suppresses any stray light by means of the multi-staged baffle (the sharp edges).

    In the last two images, we see the part coated with optical black paint (SKYMAP 35), again suppressing stray light from the fibres. Obviously, that is a little less photogenic than the uncoated part.

    Oh, before I forget; it was made by our best people.

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    © Photographs by Rik ter Horst

    Words are not enough, to describe this beautiful piece of milling art. What we see here is the mechanical interface on which one of the four fibre-populated slit-heads will be positioned.

    A slit-head holds 609 to 960 optical fibres, each of which is placed at a particular position in the focal plane of the telescope, to collect the light from a particular celestial object like a star or a galaxy. It then accurately guides the light from these fibres into the WEAVE multi-object spectrograph.

    Back to the piece of art: what strikes us are the sharp edges, located in deep pockets, the smooth machined planes and neatly chamfered edges. The part provides stiffness (and thus position accuracy) to the slit-head, and suppresses any stray light by means of the multi-staged baffle (the sharp edges).

    In the last two images, we see the part coated with optical black paint (SKYMAP 35), again suppressing stray light from the fibres. Obviously, that is a little less photogenic than the uncoated part.

    Oh, before I forget; it was made by our best people.

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  • 05/25/17--17:00: Purple Stork
  • © Dan Stinebring

    No words could improve on this evocative image, dripping with metaphores.

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    © ASTRON

    Since around 2013, a novel renewable energy concept has been explored by 14 institutes and companies, supported by EC's FP7. Dubbed Biostirling for SKA (or B4S in short) it aims at showing that this concept could generate a stable power level for (among others) radio astronomy, using focused solar energy in combination with biogas. The project started as an ambitious system approach, with up to 8 telescopes. But given the novelty and costs, we had to settle for a single demonstrator, that nevertheless works! So all participants were invited to a final meeting on April 27 in Moura/Contenda, Portugal, to contemplate success in this remote, hot and radio-quiet area.

    2 boxes with equipment were shipped to the Polytechnic Institute of Beja, where Nuno Pereira took care of the shipment. Because our Nico Ebbendorf was in China for the NCLE project, our former colleague Dion Kant flew in to take over. He was joined by Domingos Barbosa from IT Aveiro, Portugal. Since the Biostirling engine was still undergoing finishing touches, only limited RFI testing could be done. Rob Millenaar (ASTRON) and others did site tests earlier and the MPIfR did so at the Swedish company delivering the machine.

    The pictures give some flavor of site and tests, and the general excitement. I was happily surprised that the power stabilized at about 4kW, using Sun plus gas in any combination (note the cloudiness at the time). One of the pictures shows Domingos and Dion in front of the tent that was used as cover for the equipment! Another picture gives an impression of the telescope control box, naming all participants and on another those who were involved in front of the system at large.

    See for more info on the project that has now entered its final reporting stage. Very soon an educational movie will appear explaining more. Hopefully, follow-up projects will emerge, allowing us to savour the great hospitality of the Portuguese, plus the favourable conditions of the Contenda (test)site!

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    © Filippo Maccagni, Raffaella Morganti, Tom Oosterloo

    Absorption line studies are an efficient way to trace the content of neutral hydrogen (HI) in radio sources and the interplay between the nuclear activity and the cold gas. A survey that was carried out with the WSRT shows HI in almost 30% of the sources, making the planned upcoming surveys with Apertif extremely promising.

    Apertif, the new phased array feed of the Westerbork Synthesis Radio Telescope (WSRT), will start surveying the northern sky in search of neutral atomic hydrogen (HI) in radio sources (10^22 W/Hz

    We detected a great variety of absorption lines, with different shapes, widths and optical depths, shown in the image. Neutral hydrogen with kinematics deviating from regular rotation is traced by asymmetric broad lines with a with a significant blue-shifted component. This is found more often in powerful radio sources, where the radio emission is small, possibly because the radio nuclear activity is young. The same is found for sources that are bright in the mid-infrared, i.e. sources rich in heated dust. In these sources, the HI is outflowing likely under the effect of the interaction with the radio emission. Conversely, in dust-poor galaxies, and in sources with extended radio emission, at all radio powers, we only detect HI distributed in a rotating disk.

    This is a very promising result in view of what we hope to see with the upgraded Apertif. The SHARP survey (Search for HI absorption with Apertif) will expand the results of this pilot project. The SHARP survey will be complemented by the FLASH and MALS HI absorption surveys of ASKAP and MerKat respectively. Together they will probe the presence HI up to a look-back time of 9.2 billion years.

    The results are part of the PhD thesis of Filippo Maccagni and are presented in a paper Kinematics and physical conditions of HI in nearby radio sources. The last survey of the old Westerbork Synthesis Radio Telescope by F. M. Maccagni, R. Morganti, T. A. Oosterloo, K. Gereb and N. Maddox accepted for publication in Astronomy & Astrophysics,

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    © NN

    Your editor has been waiting for an opportunity to run this image. Oleg Smirnov will be in Dwingeloo for the rest of the week. If we are lucky he might even give one of his inspiring talks(*). In any case he will give one at WimSym77, on July 6th.

    (*) In fact he will, at the thursday 12:30 software lunch, in de Hooghoudt room

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    © Thomas Marsh

    Last year a remarkable fast-spinning white dwarf was found that might be a white dwarf analogue of (neutron star) pulsars. The white dwarf which spins with a period of 2 minutes is located within a close binary system. The system as a whole features very broad-band synchrotron emission and exceedingly strong pulsations, which at optical wavelengths can cause it to brighten by more than a factor of 5 in 30 seconds. It is the first white dwarf to show periodic pulsations at radio frequencies.

    In this talk I will set the context of this object, describe its unique observational characteristics, including new data taken since the discovery paper. I will also outline the considerable theoretical challenges faced in understanding this unique star the existence of which is currently unexplained.

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    © Meppeler Courant

    Given the special place of ASTRON (and JIVE, and NOVA, and DOME) in the hearts of the local people, it is not surprising that a new Director is important news. Especially the fact that she is the first woman to lead the famous institute has been received well in enlightened Drenthe province.

    The picture shows a full-page interview published by the Meppeler Courant on May 5th. Those who can read Dutch are encouraged to click on the image to read the entire article.

    NB: Also the book mentioned in the text is highly recommended.

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    © ASTRON

    After five years of hard work at the ASTRON & IBM Centre for Exascale Technology, the Dome team presented their latest results at the Dome Symposium on May 18-19. These efforts aim at preparing for the exascale era in radio astronomy, more specifically for the Square Kilometre Array (SKA). Naïve scaling of conventional technologies would yield a telescope requiring in the order of a gigaWatt to run, and even Moore's law will not be able to completely bridge the gap between what is desirable and what is possible.

    The Dome project therefore focused on Green Computing that addresses technologies to radically reduce the power needed to do computationally intensive work on extremely large amounts of data, Nano-Photonics that addresses technologies needed to drastically reduce the power of data transport over longer distances and inside computing machines, and Data & Streaming that addresses technologies to process data on-the-fly and store data at a high efficiency for later use.

    Indeed, with well over one hundred peer-reviewed publications, tens of architectures proposed and demonstrated in both computing and photonics, tooling created for storage and computer architecture modelling, several tens of SKA design reports produced, and by supporting an active Users Platform with thirty members, the Dome project has shown paths towards exascale, and can truly be considered a success.

    The symposium addressed all of this by giving an overview of the designs and of the data and computing challenges posed by the SKA, and subsequently zooming in into specific areas where Dome contributed and where Dome proposed designs that significantly improve efficiency. The Symposium made clear we have taken big steps towards our "dot on the horizon", but that we are not there yet.

    Symposium link:

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  • 06/05/17--17:00: Lunar images
  • © Rik ter Horst

    Lovely, those quiet nights in the spring. Not only for a drink or a small campfire but also for some observing under rather favourable conditions.

    The set of images presented here were made on two different occasions earlier this spring with my 40 cm F/3 telescope equiped with an ASI120MM camera. Each image is the result of a stack of about 1000 frames, post-processed with some wavelets in order to reduce the effects of turbulence. Even on those quiet nights ;-)

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  • 06/06/17--17:00: Anne Koster retires
  • © Nico Ebbendorf and more

    After 43 years, our colleague Anne Koster will leave ASTRON and start a well-deserved retirement. Although Anne is not broadly known outside ASTRON, his work has involved almost all electronic projects that have passed through the electronic laboratory in 4 decades. Whatever design came off the design table, Anne was able to assemble tit with high quality, even as the components became smaller over the years and are barely visible now.

    Anne started back in 1974 as an electronic technician and over the years he participated in many projects including 2 upgrades of the WSRT MFFE/IVC systems in the 90's, and APERTIF more recently. Also unique in Anne's carrier is that he worked on 3 world-class radio telescopes, Dwingeloo, WSRT and LOFAR.

    The pictures show Anne together with colleagues Paul Riemers, Yde Koopman, Sjouke Zwier, Rob Millenaar and Nico Schonewille in the 80's lab, and a recent picture where Anne is teaching a Vapour Phase soldering machine how to make a proper high quality soldering joint.

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    © Gabor Orosz

    Traditionally, VLBI astrometry is achieved by phase referencing observations using a close-by calibrator, where the errors are dominated by the target-calibrator separation. However, at low VLBI frequencies the spatial variations in the ionospheric contribution degrade the accuracy of traditional phase referencing, making sensitivity-limited astrometry an arduous task. MultiView is a multi-calibrator approach that characterizes the sky plane phase screen, allowing interpolation of the calibrator phase solutions to the line-of-sight of the target. This solves for the ionospheric error terms that drive astrometric uncertainty at low VLBI frequencies.

    In this colloquium I am going to

    1, discuss low frequency VLBI astrometry and the development of the MultiView technique,

    2, compare the astrometric accuracy of MultiView and phase-referencing techniques, and

    3, show applications of MultiView in maser/pulsar science and its SKA era potential.

    The figure above shows calibrated visibility phases of an AGN source at 1.6 GHz using MultiView (MV, black) and phase referencing (PR) solutions with a calibrator at 2º (red), 4º (green) and 6º (blue), on a subgroup of representative VLBA baselines in two epochs a month apart. Slow phase drifts after conventional phase referencing indicate residual systematic errors, which are different in the two epochs and depend on the ionospheric weather conditions. The MultiView phase residuals are the smallest in all cases and show no systematic trends. They are also similar in both epochs, indicating the effective mitigation of phase errors regardless of weather conditions.

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