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

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  • 08/27/18--17:00: VLBI fringes with MeerKAT

    In February 2018, the recently inaugurated MeerKAT array co-observed with one of the European VLBI Network's (EVN) Network Monitoring Experiments (NME) 'N18L1'. Beamformer spectra and single dish voltage time series were captured from the MeerKAT system by SARAO (South African Radio Astronomy Observatory) staff.

    As MeerKAT's sampling rate and data formats are not yet VLBI compatible, software was developed by JIVE staff(*) to extract and resample 2 x 32 MHz, overlapping with the 8 x 8 MHz bands observed by the EVN stations, and reformat it to the VLBI Data Interchange Format (VDIF).

    Shown are fringes between one MeerKAT (Me) dish, m011v, and the EVN stations Effelsberg, Germany (Ef) and Hartebeesthoek, South Africa (Hh) in all eight EVN bands. They appear in LR and RR polarization because the MeerKAT receivers are linear whilst VLBI telescopes observe in circular.

    Finding VLBI fringes using a single 13.5 m MeerKAT dish on an 8000+ km baseline clearly demonstrates the excellent quality of the dish and receiver system. Fringes were also found using the beamformed output, using the same signal processing chain. These, however, are still under investigation.

    This result, while modest, is an important first step(**) towards including the phased-up MeerKAT in global VLBI observations, and, eventually the SKA.

    These fringes are the result of a close cooperation between staff at the SKA-SA/SARAO office and JIVE.

    (*) Entirely in python, with help from the numpy and SciPy modules

    (**) It takes over an hour to extract ten seconds worth of data from the single dish time series. Converting the complex spectra from the beamformer takes an order of magnitude longer.

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    © ASTRON

    Using the interferometric and beam formed capabilities of LOFAR, we analysed the propagation of a group of Type III radio bursts observed on 30 March 2018, in the height range from ~1.5 Rsun to ~4 Rsun in the solar corona, which corresponds to the harmonic plasma frequency emission from 80 to 20 MHz. Taking advantage of the interferometric high spectral and temporal resolution of LOFAR ( 160 ms / 196 kHz ), we were able to distinguish five different paths of propagation for the electron beams in the type III group.

    In addition, with the simultaneous LOFAR beam formed full Stokes observations, (frequency and time resolution of 10 ms and 12 kHz, respectively), we estimated the coronal magnetic field along these five electron beam paths. This was done by calculating the degree of circular polarisation using the IQUV spectra of the harmonic plasma emission from the type III bursts (Kumari, Zucca et al. in prep.).

    Supervisor: Dr. Pietro Zucca (ASTRON)

    Co-Supervisor: Dr. Sarrvesh Sridhar (ASTRON)

    This data set is part of LOFAR LC9_002 cycle data (PI - P. Zucca)

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    © ASTRON

    Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. Sometimes we are lucky enough to observe the remnant plasma of a previous phase of jet activity together with a new pair of restarted jets. These kind of sources offer us the occasion to study the timescales of the jet life cycle, which are to date still poorly understood. Because the large-scale radio emission tend to fade in the remnant phase of the source, the great sensitivity of LOFAR is ideal to study these objects (see also Daily Image 19-09-2017 .

    In this work we have investigated the duty cycle of the radio galaxy B2 0258+35, which was suggested by Shulevski et al. 2012 to be a restarted radio galaxy based on its morphology at 1.4 GHz observed with WSRT (see figure on the left). The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (240 kpc) with relaxed shape and very low surface brightness that resemble remnants of a past AGN activity.

    New LOFAR observations at 145 MHz have clearly detected the emission of these lobes (see figure on the right). The combination of these data with the WSRT and new observations with the Sardinia Radio Telescope at 6600 MHz has enabled us to investigate the spectral properties - and therefore the age - of the outer lobe over a very broad frequency range.

    Interestingly, the spectrum of both the Northern and Southern lobe is not ultra-steep (spectral index 0.5-0.7) or significantly curved as expected for an old ageing plasma. We suggest that mechanisms such as in-situ particle reacceleration, mixing or compression may be temporarily playing a role in preventing the spectrum from steepening. However, it seems unlikely that the outer lobes are very old remnants of past activity as previously suggested (with age > 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched of no more than a few tens of Myr ago, allowing us to observe both the inner and outer structure simultaneously.

    This study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations with LOFAR are revealing around a growing number of radio sources.

    If you wish to learn more about this source have a look at our recent publication on Astronomy & Astrophysics Brienza, M., Morganti R. et al. 2018 Duty cycle of the radio galaxy B2 0258+35 .

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    © Paul Boven (JIVE/CAMRAS)

    On Wednesday the 29th of August 2018, the Dwingeloo radio telescope took part in a test VLBI observation and we managed to obtain fringes to Westerbork and Jodrell Bank right away. This is more than 40 years after its first appearance as a VLBI telescope (see Schilizzi e.a., A&A 77, 1979).

    The Dwingeloo telescope, once the largest fully steerable dish in the world, is now operated by the CAMRAS volunteer organisation. They have, with great support from ASTRON, restored and rejuvenated the historical instrument. Its return to VLBI is a huge milestone and a testament to the great work by all these volunteers.

    The image shows the fringes in one of the 8 subbands of each 16 MHz that were recorded. The background image depicts the 'flowchart' created in the open source GnuRadio program to convert the input from raw samples, into properly timestamped VDIF data for the JIVE correlator.

    Just like the previous time that Dwingeloo did VLBI, the frequency reference is again a borrowed Rubidium clock. However, as part of the ASTERICS project, we are working to transport the H-maser frequency reference signal from Westerbork over fiber to the Dwingeloo telescope. This still requires a bit of digging to bridge the last few hundred meters to the telescope, but expect even better fringes soon.

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    The first cohort of the ASTRON/JIVE traineeship programme in science operations with massive arrays was successfully completed by two participants, Emmanuel and Bernard from Ghana. The programme allows astronomers (post doc, PhD or graduate student level) to spend a trimester (12 weeks) at the institute in Dwingeloo in the Netherlands. It enables the acquisition of expertise in operating massive arrays such as LOFAR and the EVN, therefore developing skills that will be required for the operation of next generation facilities such as the SKA.

    The program included 11 weeks of full exposure to LOFAR operations, and 1-week of training in VLBI operations and science at JIVE. Trainees were assigned mentors within the Science Support Teams at ASTRON and JIVE, under which they learned how to master independently the complex array science operations of the operated instruments, and strongly benefited from the daily interaction with scientists, engineers, and support staff.

    The traineeship also featured lectures and activities with the support groups such as visit to the LOFAR telescopes, Correlator (Cobalt and EVN), LTA (SURFsara), and the WSRT. During these, the trainees were given expert tours of the respective facilities to understand the operations and role of each infrastructure in the overall science capabilities of the instruments.

    The programme was sponsored by ASTRON and the Joining up Users for Maximising the Profile, the Innovation and the Necessary Globalisation of JIVE (JUMPING JIVE) which received its funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730884.

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    © Neal Jackson/Long Baseline Working Group

    Each frame of this movie shows the derived phase correction (left) of a number of different sources in the Long-Baseline Working Group test field, on the baseline from Exloo (phased-up core stations) to Effelsberg. The movie is based on an 8-hour observation, and phase corrections and imaging have been done by hand (although we are working to automate the process!) Phases are referenced to 1327+5504, the bright source towards the right-hand side of the picture, and are colour-coded on a colour loop (cyan=0). Note the slow variations close to the reference source, and the faster and more high-amplitude variations further from the reference source. The right hand panel shows the ionospheric delay relative to 1327+5504, with a colour scheme ranging from pink (-100ns) to white to yellow (100ns). Only one source is bright enough to derive good delays.

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  • 09/04/18--17:00: YERAC 2018!
  • © JIVE

    This year's conference covers giant radio pulses, double neutron star systems and solar corona, with a lot more in between! Each participant has 17 minutes to showcase some of the exciting research from the upcoming generation of radio astronomers. The Young European Radio Astronomers Conference (YERAC) 2018 is taking place this week (4-6th September) following a collaborative organisational effort from JIVE and ASTRON.

    We welcome 32 participants to Dwingeloo to discuss their research among peers. 2018 marks 50 years since YERAC was originally coordinated by Emile Blum, Harry van der Laan and Peter Mezger. After meeting at NRAO in the US the trio wanted to find a way to bring young European astronomers together to meet and exchange ideas and experiences.

    Many of the ASTRON and JIVE community have attended YERAC and have benefitted from the collaborations that stemmed from this meeting. We wish this year's participants the best of luck with their future endeavours!

    The Local Organising Committee for YERAC2018 consisted of Ilse van Bemmel (JIVE), Katharina Immer (JIVE), Yvonne Kool (JIVE), Gina Maffey (JIVE), Robert Schulz (ASTRON) and Marjan Tibbe (ASTRON). This event has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730562 (RadioNet).

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    © Quokka image modified based on picture credited to by buzzfeed and including map of the Galactic Rotation Measure foreground (Oppermann et al 2015, A&A 575, 118); all others G. Heald.

    With the advent of broadband frequency coverage on modern radio interferometers - an advancement led by telescopes like the WSRT - we are entering a new age of radio polarimetry. Exquisite broadband polarimetry provides a unique view on the detailed magnetic and ionised structure within radio-emitting objects such as star-forming galaxies and AGN. We also have unique access to the time variability of magnetic structures within sources, in a manner complementary to VLBI observations.

    In this presentation I will describe new, ongoing survey efforts in this direction across a wide range of frequency using Australian radio telescopes: the Murchison Widefield Array (MWA), the Australian SKA Pathfinder (ASKAP), and the Australia Telescope Compact Array (ATCA). This overview will include new data and new results, and will star a few marsupials. I will also place this fresh observational progress in the context of the extraordinary magnetism science that is now being enabled by LOFAR. The talk will conclude with some thoughts on the future of this field as we move toward the era of the SKA itself.

    About the image: Clockwise from top-left: The ATCA, a happy quokka, ASKAP, and the MWA. Central image: A plot of a Faraday dispersion function (FDF) from the QUOCKA survey, which leverages detections of polarized sources made with ASKAP and follows them up with broadband polarimetric observations using the ATCA.

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  • 09/06/18--17:00: LOFAR from a hot air balloon
  • © ASTRON

    Last week, one of our LOFAR neighbours enjoyed a hot air balloon flight over the province of Drenthe. It gave magnificent views on his own croplands but as the wind took them further north, they also crossed our LOFAR core. This picture was taken from the balloon. The reflection of light in the water surface beautifully highlights the unique location of our instrument in its natural surroundings.

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    © Photos: ASTRON, Youtube movie: TU Eindhoven

    In the SKA/LFAA telescope the signals that are received by its antennas are transferred directly to a central signal processor without any intermediate signal processing/data reduction steps. In the past years ASTRON has developed photonic transmitter/receiver technology for the fibre-optic transfer of these signals. Currently ASTRON is working on a further development of this electronic/photonic technology for future telescope systems. In this work attention is focused on the development of custom designed integrated photonic devices which are tested by ASTRON with the use of demonstrator systems like the MEMPHIS demonstrator tile that is displayed in the R&D hall (see picture below). For the fabrication of the custom designed Photonic Integrated Circuits (PICs) ASTRON makes use of fabrication facilities that are offered by e.g. the Joint European Platform for Photonic Integrated Components and Circuits (JePPIX, Some time ago a short movie was made by JePPIX (see: ) which explains their work and (at 1:17) the way that ASTRON contributes to the development of the emerging PIC fabrication infrastructure in the Netherlands.

    The pictures show (left) the photonic demonstrator tile that was developed in the MEMPHIS framework ( and (right) the InP and TriPleX PICs in the demonstrator system.

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  • 09/10/18--17:00: Open Dag / Open Day
  • © ASTRON

    Kom op zaterdag 6 oktober tijdens het Weekend van de Wetenschap naar de open dag van ASTRON en JIVE en leer alles over de grootste (radio)telescopen ter wereld!

    Hoe ontvangen we signalen uit het heelal? Hoe zien de nieuwste telescopen eruit? En wat heb je nodig om die te bouwen? Bij ASTRON ontdek je het.

    Doe proefjes en experimenten die te maken hebben met het heelal. Ga op reis door de ruimte in het mobiele planetarium. Leer programmeren en maak je eigen ontplofte ster!

    Heb je vragen die je graag aan onze sterrenkundigen en ingenieurs wilt stellen? Verzamel ze, neem ze mee en stel ze tijdens de open dag. Heb je daarnaast altijd al een kijkje willen nemen in de Dwingeloo Radiotelescoop?

    Dat kan ook dit jaar weer! CAMRAS organiseert allerlei activiteiten in en rondom de radiotelescoop. Kijk voor meer informatie hierover op .

    Neem iedereen mee op 6 oktober naar Dwingeloo. Jullie zijn allemaal welkom in de wereld van de radioastronomie!

    Find out how the world's largest (radio) telescopes are built!!

    JIVE and ASTRON will be holding an open day on Saturday 6th October, during the Weekend of Science (Weekend van de Wetenschap)!!

    You can conduct your own experiments, take a journey through space in the mobile planetarium, learn computer programming and even make your own pulsar!!

    Do you have questions about astronomy? Our astronomers and engineers will be there to answer them!

    Plus, you can also have a look in the Dwingeloo Radio Telescope! CAMRAS organises all sorts of activities in and around the radio telescope. For more information, visit

    Everyone is welcome to explore the world of radio astronomy!

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  • 09/11/18--17:00: thermal Graduate
  • © G. Schoonderbeek

    End of June our Mechanical Engineering Graduate - Jesper Spraakman held his final project presentation at ASTRON about generic cooling solution for the Gemini LRU board.

    Thanks to his enthusiastic input we obtained a working prototype, broadend our knowledge even more about the do's and dont's of heat pipes, and most importantly he indicated to a slightly broader public (outside the Mechanical Group) that thermal design and cooling of electronics is not a trifle and needs to be addressed by a multidisciplinary team with particularly substantial attention starting from the very early stages of a project.

    Jesper, well done! Congrats on your good grade and on behalf of the Mechanical Group and Perentie team I wish you good luck in your future endavours!

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    © ASTRON

    With an innovative new type of receiver, called Apertif, the field of view of the Westerbork Synthesis Radio Telescope in the Netherlands has been increased 37 times. Apertif, developed by the Netherlands Institute for Radio Astronomy (ASTRON), will be officially opened on 13 September 2018 by deputy Cees Bijl of the Drenthe province. On this day the 50-year anniversary of the telescope will also be celebrated.

    The iconic 50-year old Westerbork Synthesis Radio Telescope (WSRT) has been upgraded with a new high-speed, wide-field radio camera called Apertif. Using a technique called beamforming, 12 of the 14 dishes are now able to map a part of the sky that is 37 times larger than before. Apertif is also a pathfinder of the Square Kilometre Array (SKA), the future largest and most sensitive radio telescope in the world, recognized by the SKA project.

    Het blikveld van de Westerbork Synthese Radio Telescoop is 37 keer vergroot dankzij Apertif, een innovatief nieuw type ontvanger. Apertif, ontwikkeld door het Nederlands Instituut voor radioastronomie (ASTRON), wordt op 13 september 2018 officieel geopend door gedeputeerde Cees Bijl van de provincie Drenthe. Op deze dag wordt ook het 50-jarige jubileum van de telescoop gevierd.

    De iconische 50-jaar oude radiotelescoop in Westerbork heeft in 12 van de 14 schotels een nieuwe set camera's gekregen. Met behulp van een techniek genaamd beamforming kan nu in een waarneming een deel van de hemel in kaart worden gebracht dat 37 keer groter is dan voorheen. Apertif is ook een door het Square Kilometre Array (SKA) project erkende voorloper van SKA, de toekomstige grootste en meest gevoelige radiotelescoop ter wereld.

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    © Roy de Goei /

    This year Leeuwarden-Fryslan 2018 is the Cultural Capital of Europe. One of the major project is the 11 fountains in the eleven Frisian cities, designed by eleven artists from different countries.

    One of these fountains is created by the french artist Jean-Michel Orthoniel, called 'the Oort-Cloud'

    The fountain is an ode to the famous astronomer Jan Hendrik Oort, who was born in Franeker. His assumption that 'cloud' of billions of comet-like objects moving around our solar system was a breakthrough in astronomy.

    The fountain is designed as a series of waterfalls spilling that flow into the water basin from a bowl, along a vertical chain of night-coloured pearls. One of the pearls is silver-coloured, like the colour of the moon, another is gilded, the colour of the sun.

    The 'Oort Cloud' fountain itself is a mist of fine droplets falling from a gold-coloured mesh into the bowl.

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    © Krzysztof T. Chyzy et al.

    LOFAR's Multifrequency Snapshot Sky Survey (MSSS) has resulted in extensive studies of a large sample of nearby star-forming galaxies. Using the measured 150-MHz flux densities from MSSS and flux densities at various frequencies from the literature, we have obtained integrated radio spectra for 106 galaxies. This image illustrates examples of such spectra, showing that they are generally flatter at lower compared to higher frequencies. However, as there is no tendency for the highly inclined galaxies to have more flattened low-frequency spectra, we came to the conclusion that the observed flattening is not due to thermal absorption, contradicting previous suggestions.

    The interpretation of the observed spectra was performed with a three-dimensional numerical model of galaxy radio emission, and radiation transfer dependent on the galaxy viewing angle and absorption processes. Our modelling suggests that the weak spectral flattening observed in the nearby galaxies results principally from synchrotron spectral curvature due to cosmic ray energy losses and propagation effects. We predict much stronger effects of thermal absorption in more distant galaxies with high star formation rates. We also show that integrated spectra alone cannot be properly interpreted without supplementary data on the properties of the local interstellar medium within the galaxies.

    If you wish to learn more about MSSS results and modelling of galaxy spectra, please look at our recent article - (K. T. Chyzy et al. 2018) - which is now accepted for publication in Astronomy & Astrophysics.

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  • 09/17/18--17:00: 5th LOFAR Data School
  • © Vanessa Moss

    This week ASTRON will host the 5th LOFAR data school. 51 participants from 14 countries will be introduced to the LOFAR system. The participants will follow lectures and tutorials that cover the many aspects of the LOFAR system from the capabilities of the basic station hardware to the software pipelines and science products they produce and will learn how to analyse both interferometric and beamformed data from LOFAR.

    More information about the school and the program can be found at the LOFAR data school website.

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    © ASTRON

    On 30 August we successfully delivered, installed and tested our Microserver Datacenter at the EnTranCe center of the Hanzehogeschool in Groningen. EnTranCe will perform energy efficiency measurements and student assignments on the datacenter.

    The Microserver Datacenter was developed by IBM and ASTRON in the DOME project. It contains server class compute nodes based on a system on a chip (SoC) with SATA, networking, serial port and boot FLASH interfaces on the same chip. Microservers are densely packed clusters of low power servers running computationally light workloads between thousands of processor cores.

    A fully populated 2U microserver datacenter housing contains 64 nodes. Each node contains one T4240 PowerPC processor with 12 cores, so a full housing contains 768 cores! Our datacenter is equipped with 8 nodes. The datacenter is water cooled and contains a network switch to route the traffic between the nodes and the outside world. It also contains an mSATA SSD card with one 240GB SSD for each processor.

    This activitiy is performed as part of the project Valorisation Microserver. By a consortium of SMEs and Knowledge institutes located in the Northern part of the Netherlands, this project is investigating the commercial prospects of this new design approach for densely packed highly energy efficient Micro data centers.

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    © Frank Nuijens

    September 3rd marked the start-up of a new activity at ASTRON, the project: ''Utilisation of LOFAR in SSA SWE Services'' funded by ESA and will run for 12 months.

    The aim of this in-house project is to explore and demonstrate how data products derived from LOFAR data may in the future benefit in the ESA Space Situational Awareness programme (SSA), space weather (SWE) service network.

    During the project we will focus specifically on studying promising possibilities in three areas: Solar, Heliospheric, and Ionospheric data products. The activities include an analysis of the requirements of the ESA SSA SWE network, and consultations with the ESA Expert Service Centres of the three domains as well as with end users of the network in the Netherlands regarding tailored demonstrations products. During the last phase of the study we will present the requirements and further steps necessary in case some particular LOFAR data products are incorporated into the ESA SSA SWE network.

    The photograph was taken during the kick-off meeting of this activity that took place at ASTRON on July 26, in the presence of ESA representatives Alexi Glover (space weather service coordinator) and Federico da Dalt (space weather applications scientist). Richard Fallows is the project scientist, Carla Baldovin the project manager, and Rene Vermeulen the project coordinator. Bert van den Oord from KNMI joined the meeting as representative of the Ministry of Infrastructure and Water Management and in his role in the national space weather network SWENED. Among the participants we also had members of ASTRON involved in other current space weather activities.

    We look forward to a very productive 12 months!

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    © Benito Marcote & MAGIC Collaboration

    FRB 121102 is the only known repeating Fast Radio Burst (FRB), and the only FRB that has been localized to sub-arcsecond resolution. The nature of this source and all other FRBs remains unknown, and the mechanisms producing these bursts also remain unclear. One key question still to be clarified is if these bursts also produce emission at other wavelengths. Whereas some scenarios point to an emission confined to radio wavelengths, others predict emission at much higher energies.

    To better understand FRB 121102 we have conducted simultaneous observations within the Arecibo Telescope and the MAGIC Telescopes. Although the MAGIC Telescopes mainly observe at very high energy gamma-rays (>200 GeV), we also used the central pixel (an optical photosensor originally designed to observe the optical Crab pulses) to constrain the putative optical emission from FRB 121102.

    We detected five radio bursts within these observations. However, very high energy emission was not detected, neither of a persistent nature nor burst-like. We constrained the average luminosity to be 45 erg/s above 100 GeV, and 49 erg/s for bursts at the times of the observed radio bursts. Interestingly, we have put the most stringent limits to the putative optical burst emission to date, with upper limits of 8.6 mJy at 5-sigma level for 1-ms emission. We detected an optical burst of 29 mJy with a duration of 12 ms 4.3 s before one of the radio bursts. However, this signal cannot be univocally linked to FRB 121102 and it is consistent with a background signal.

    The obtained results have several implications for constraining the current FRB models, and you can read the detailed discussion in the paper titled: Constraining very-high-energy and optical emission from FRB 121102 with the MAGIC telescopes, which is published MNRAS, Volume 481, Issue 2.

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    © ASTRON

    Last week the formal start of 12 Westerbork dishes in the widefield era started with the "Apertif" festivities in Westerbork.

    This occasion also marked the end of the use of all Westerbork dishes as 14 single pixel dishes using the "Westerbork 2000" system.

    The rich history of the WSRT of course can not be left unmarked and initiated by the ASTRON MT, has now been captured in the book "50 years Westerbork Radio Observatory. A continuing Journey to Discoveries and Innovations". This 350 pages book was presented at the Apertif occasion by Arnold van Ardenne as chief editor besides co-editors Richard Strom and Steve Torchinsky. It is dedicated to Ger de Bruyn whose untimely passing away last year, left a hole as champion user, science visionary and great personality. Among the books 18 chapters is a chapter which largely captures Ger's "personal discovery table" ranging form 1970 to 2015 in which year 12 of the 14 Westerbork dishes were prepared for Apertif. The exciting 50 years Westerbork journey is described and well illustrated by the over 50 authors also making it a "peoples achievement book".

    For those who were closest involved besides the editors, i.e. Truus van den Brink, Frank Nuijens and Harm Jan Stiepel and of course the publisher who "shaped the book"" in its present nice form, we are proud to present it to all contributors, ASTRON employees and those who were present at the Apertif opening!

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