© 14th EVN Symposium and Users meeting

Alongside a variety of talks, the EVN users meeting and the EVN vision meeting were held. In the users meeting, JIVE staff gave a summary of the status of the EVN and users provided feedback about the usability of the array. In the EVN vision meeting, the scientific future of the EVN was discussed.

In addition, a CASA-VLBI workshop, organized by JIVE, was offered at the end of the meeting, which gave participants the opportunity to get to grips with developments that enable VLBI analysis to be done using the CASA software programme.

On the social side, the local organizing committee set up a night visit to the stunning Nasrid Palace at the Alhambra as well as a trip to the IRAM 30m telescope, offering the perfect locations to catch up with old and new colleagues from across the VLBI network.

© 14th EVN Symposium and Users meeting

Alongside a variety of talks, the EVN users meeting and the EVN vision meeting were held. In the users meeting, JIVE staff gave a summary of the status of the EVN and users provided feedback about the usability of the array. In the EVN vision meeting, the scientific future of the EVN was discussed.

In addition, a CASA-VLBI workshop, organized by JIVE, was offered at the end of the meeting, which gave participants the opportunity to get to grips with developments that enable VLBI analysis to be done using the CASA software programme.

On the social side, the local organizing committee set up a night visit to the stunning Nasrid Palace at the Alhambra as well as a trip to the IRAM 30m telescope, offering the perfect locations to catch up with old and new colleagues from across the VLBI network.

© Astron

Arturs and Karlis, from the Ventspils International Radio Astronomy Centre (VIRAC) in Latvia, just finished the Uniboard firmware training, part of the BALTICS project. In this firmware training they used existing RadioHDL FPGA firmware libraries, made by the DESP group at ASTRON, to program the Uniboard. Arturs and Karlis found their way through the firmware design tasks and even enhanced the user interface with their creativity in Python and VHDL programming.

BALTICS is an educational program funded by the European Union. It is meant to share the expertise of the University of Manchester and ASTRON with the staff of the VIRAC. With this successful training result, they can continue at VIRAC, where they have 2 Uniboards already.

© Colloquium

© ASTRON / Top Foto

This design loop: requirements, design, verification, followed by adaption, usually is sequential and iterative. But does it always need to be so? What if one would include costing models explicitly in the designs at the same level as the scientific figures of merit such as sensitivity? This was what we have looked into after the idea was coined by Jaap Bregman in 2005 (in SKA: an Engineering Perspective, Springer).

Both scientific figures of merit (F) and costing (C) depend on telescope design parameters (p) such as number of telescopes and observing bandwidth. Optimal values for these parameters can be found using an elegant optimization approach: Lagrange multipliers (see picture for the basic formulas). Details can be found in our paper (Oct. 2018, doi: 10.1029/2018RS006624), where we conclude that the LOFAR 2010 designs are very close to the optimal ones, and where we have assessed the 2017 SKA1-Low designs.

As it probably will remain difficult to include all science requirements, all non-functional constraints, and all design options in one tractable model, the design process will remain iterative. However, by including cost explicitly in the first design steps, big de-scoping actions late in the design cycle can hopefully be avoided.

© Sridhar, Heald & van der Hulst (2018)

The massively parallel General Purpose Graphical Processing Units (GPGPUs) can be used to execute some of the computationally intensive astronomical image processing algorithms including RM synthesis. In this paper, we present a GPU-accelerated code, called cuFFS or CUDA-accelerated Fast Faraday Synthesis, to perform Faraday rotation measure synthesis. Compared to a fast single-threaded and vectorized CPU implementation, depending on the structure and format of the data cubes, our code achieves an increase in speed of up to two orders of magnitude. The code is written in C and supports both FITS and HDF5 file formats. The code is available at https://github.com/sarrvesh/cuFFS .

The image on the left shows a single Faraday depth plane computed with cuFFS using data from the WSRT SING survey (Heald et al. 2009). The plot on the right shows the pixel-by-pixel comparison of the cuFFS output with a CPU implementation.

The paper describing cuFFS has been accepted for publication with Astronomy & Computing and the preprint is now available online ( http://arxiv.org/abs/1810.06250 ).

© astron

It was October 2001 when Truus started at ASTRON as a secretary to Arnold van Ardenne and the Research & Development department. And during the start-up of Astrotec Holding, Truus assisted as office manager.

The start of the SKA Design Studies (SKADS) project also marked the start of a new staff division Emerging Technologies. Truus accompanied Arnold to the new division and provided secretarial support to the international SKADS Management Team and Board.

Later, after the finalisation of the SKADS project, Truus started to provide management assistance to Marco de Vos. In 2012 Truus also aided Michiel van Haarlem in the NL SKA Office.

During the 17 years at ASTRON Truus provided secretarial support for the Dutch The International Union of Radio Science (URSI) committee, besides Truus also organised several events for URSI. The URSI BEJ session on Mauritius was one of the many highlights.

Besides larger projects, Truus was involved in other smaller projects. Projects like restructuring the reception, changing the ASTRON garden and the interior design of the Dwingeloo office and the meeting rooms.

We like to thank Truus for all her contributions over the last 17 years and we wish her good luck and many happy new adventures to come.

© Sandra Etoka

© ASTRON

Increasing the number of antennas to be processed at each LOFAR station obviously requires an upgrade of the station electronics. To limit the number of design options for the upcoming preliminary design review, it was decided to have a station electronics architecture assessment as a first step. For this, we conducted a broad sweep of options ranging from configurable chips (FPGAs) that have very high input-output data rates (I/O) but are difficult to write code for, computer graphics chips (GPUs) that have limited I/O capabilities but are easy to program, 'standard' computer chips (CPUs) with programming ease similar to that of GPUs, digital processor chips (DSPs) that are extremely difficult to write code for, and hybrid systems.

In our analysis we scored cost, power consumption, scalability, ease of programming, technology readiness level, dimensioning of the system, and schedule. To cut a long story short, it turned out that FPGA based systems still are the overall best choice in this part of the signal processing chain. This was both the conclusion of the architecture team and the review panel that visited us on October 3. The picture above shows Gijs Schoonderbeek explaining the different design options to the review panel.

© Caballero/MPIfR/ASTRON/NASA/JPL/IPTA

In pulsar timing, the centre of mass of the entire solar system is used as a reference point for highly accurate measurements of the times of arrival of the pulses. The work therefore needs a complete description for the solar system and the movement of all the bodies in it. This description is called a solar-system ephemeris and is created by planetary astronomers using several sources of data, including spacecraft fly-bys of the planets and moons.

If the ephemeris uses an incorrect mass for any of the objects included, this would result in an offset in the location of the centre of mass and, in turn, periodic changes in the expected arrival time of pulses from pulsars.

Using the latest published data by the International Pulsar Timing Array, including observations taken with the WSRT, this work gives an independent measurement of the masses of planets and asteroids in the solar system. The bottom figure shows the radio telescopes in the IPTA that were used for this study.

For example, the mass of dwarf planet Ceres, was determined to be only 1.3% of the mass of the Moon (shown in the top image (Moon and Earth for scale).

Although spacecraft fly-bys provide 3-100000 times more precise measurements for the different objects in our solar system, the results from pulsar timing will improve when longer data sets are available. This method gives a completely independent way of measuring the masses of objects in our solar system. Moreover, the data can be used to place upper limits on any unknown body in orbit around the Sun, like Planet Nine or even dark matter in the solar neighbourhood.

https://academic.oup.com/mnras/article/481/4/5501/5113478

© Sarrvesh Sridhar

© ASTRON

At TU/e his work focuses on various aspects such as the antenna systems, array calibration, synchronization, localization, interference mitigation, and signal processing aspects of the telescope. Having also a part-time position as head of the radio group at ASTRON, prof. Bentum is in an excellent position to make his dreams come true. During the speech, Prof. Bentum also addressed another topic close to his heart, education, by setting out his views on how to optimally engage students.

© ASTRON

This year marks the 12th such group (it's sobering to think that I've been doing this since 2007). From left to right: Zeger Ackerman, Michael Stroet, Alaya Ben-Belkacem and Thomas Goldman (here pictured during the wrap-up meeting in my office in Amsterdam). Students from previous years have gone on to do MSc and PhD research in Amsterdam or other astronomical institutes.

In recent years, the students have been analysing LOFAR data of a bright pulsar in a binary system. They need to fish through the data to find the pulsar signal, then explain why its period is changing (spoiler: because of the Doppler effect), and then model its orbit. Based on their analysis, they prepare both a written and oral report.

Many thanks to Cees Bassa for helping with supervision, and to Liesbet Elpenhof for puzzling out the logistics.

© ASTRON

One of the many activities included a Moon-walk explaining the why and how of Lunar phase and eclipses, Earth's tides, and space travel. This excursion ended at the Waagplein next to the City Hall, below a 7m diameter Moon created the British artist Luke Jerram, see picture. Having been a stadjer (*) myself I was delighted to present our ASTRON Lunar NCLE receiver work, during two general public excursions on Thursday evening.

After explaining celestial dynamics by word and by body movement, we arrived below the south pole of the Moon, where we had an awesome view despite the heavy rain. The 1969 Apollo 11 landing site was visible a bit higher-up at the 'near-side' of the Moon. At this scale, the Chang'e 4 communicaton satellite carrying our NCLE receiver, was hovering nearly two hundred metres South in the direction of the Herenstraat. We were able to spot the Chang'e4 Lunar Lander area in the Aitken crater, where it hopefully will successfully land after an envisioned launch coming Month.

(*) Groningen city people

© NOVA/Astron

The run started with warm tests: encoder performance verification, optimizing motor control, wobble- and runout- test. This week the cryostat is cooled down to 80 Kelvin (which takes 2 days!), during which temperatures are monitored and heaters are controlled with a PID loop. Cold tests are planned for end of the week.

The picture shows the prototype mounted on a temperature-regulating plateau, which is placed on the cryostat base plate.

A lot of people contribute to this project, but most of the design, manufacturing, assembly and testing is done by Gert Musters, Niels Tromp, Eddy Elswijk, Menno de Haan, Menno Schuil, Peter Kunst, Joost van den Born and Annemieke Janssen.

© ASTRON

This year I was invited by the Waddenacademie to give a lecture about my research, but with a twist: first I attended the play "Bambie is Back!" ("Oefeningen in het rekken van tijd"), and then I tried to make connections along the themes of time, the finite, and the infinite. Following my talk, myself and the actors/creators of the play engaged with the audience about these themes and the parallels between artistic and scientific creativity.

The trip to Terschelling also involved a tour of the various art installations, including a giant "geluidsspiegel" (see image top left) where one could stand and listen to the song birds in the polder below.

© ASTRON

The COBALT 2.0 team took this task head-on by successfully coming up with a super-optimized configuration involving the most appropriate set of components/CPUs/GPUs/technologies and network topologies. Thanks to their smart work, the resulting COBALT 2.0 can even do significantly more than the LOFAR Mega Mode requirements. The new correlator would be one of the most flexible and "greenest" (energy efficient) computing machines of its kind. In addition its future viability has been very well kept in mind during the design. This becomes even more impressive given the limited financial resources.

Yesterday, via a flawless and a successful tender process ( https://www.tenderned.nl/tenderned-tap/aankondigingen/143048 ), the final order for COBALT 2.0 hardware has been placed. This marks a giant step towards LOFAR Mega-Mode operations expected sometime next year.

Interested to know more? In the next few months, we will provide more details in our presentations as the next stage of challenging but exciting commissioning period commences. And most importantly, this increased efficiency of LOFAR (by several times) will lead to many more exciting scientific discoveries, in the years to come.

© Colloquium

However, while Type Ia supernova almost certainly involve the thermonuclear explosion and unbinding of a carbon-oxygen white dwarf, understanding the possible role of a binary companion and the mechanism of explosion remain open problems in supernova research. Multi-band observations including radio and X-ray have placed deep upper limits on the density of the surrounding medium and disfavour most scenarios involving a non-degenerate companion. Several other scenarios remain, and thanks to theoretical developments in the last decade, we now have a variety of 3D hydrodynamic explosion models available. These can can be tested with nucleosynthesis and radiative transfer simulations to compare to observational light curves and spectra.

The image shows synthetic spectra of a Chandrasekhar-mass model (W7) and two sub-Chandrasekhar-mass detonation models with no gravitational settling (S0) and with 5.5 Gyr of extremely efficient settling (S5.5) in the white dwarf progenitor prior to explosion. The model with more gravitational settling explodes with a greater concentration of neon-22 in the centre, which leads to more production of stable isotope nickel-58, particular noticeable in the spectral feature at 7378 A. Also shown is a typical Type Ia supernova SN2013ct observed by Maguire at al. (2016).

© R. Pizzo

ADASS is held each year at a different hosting astronomical institution. In 2019, ADASS will come to the Netherlands and will be held at MartiniPlaza, in Groningen, between 6-10 October 2019. The conference website is already live: www.adass2019.nl. The organisation of ADASS XXIX is lead by ASTRON, in collaboration with various Dutch astronomical institutions: JIVE, University of Amsterdam, University of Groningen, University of Leiden, University of Nijmegen, and ALMA ARC. Hosting ADASS in the Netherlands in 2019 will be important to give crucial exposure to the data-analysis and software techniques developed in our country and to showcase LOFAR and APERTIF to the global technical astronomy community. Indeed, the conference programme will also include tours to our observing facilities. To both advertise next year conference and show the important technologies and astronomical software we develop in our country we have set up a booth at ADASS this year. The picture shows, together with the poster of the conference, the team who has helped in this effort and who will, with the rest of the LOC, be hard at work to ensure a very successful ADASS conference next year!

© Ger van Diepen, Eric Kooistra, Alex Benjamins

4th Telescooploop, the ASTRON event to run or walk from one telescope to

another. Maybe it should be renamed to Telescooptocht because in this

edition cyclists could also take part.

After an exceptional Dutch summer it was another exceptional day with

outstanding weather, ideal for walking, running or cycling. Various

routes through the beautiful fields, heath and forests of Drenthe had been

prepared touching all 3 ASTRON telescopes: LOFAR, WSRT and

Dwingeloo. GPS tracks and paper maps were made available of all

routes which ranged from 56 to 112 km cycling and 8 to 48 km walking or running.

In total 33 people took part in the event:

- 4 cyclists did the 112 km tour Dwingeloo-LOFAR-WSRT-Dwingeloo.

- 6 cyclists did the 56 km LOFAR-WSRT-Dwingeloo route.

- 3 walkers did the 48 km LOFAR-WSRT-Dwingeloo route.

- The 24.3 km WSRT-Dwingeloo route was done by 3 runners and 4 walkers.

- A shorter part of the last route (8 or 15 km) was run or walked by

20 people.

Taxis had been organised to bring the people (and their bikes) to the

starting point of a route. The first taxi (with the 48 km walkers)

left Dwingeloo already at 6am. At the end drinks and snacks were

available in the Dwingeloo canteen where people could share their

experiences. The participants have enjoyed it a lot and many of them

asked if it could be turned into an annual instead of bi-annual event.

The Personeelsvereniging would like to thank the volunteers Alex Benjamins

and Pieter Jager who supplied the participants with food and drinks

along the route.