© ASTRON
The UniBoard2s will be used as interface between the APERTIF correlator (using 16 old UniBoards) and the GPU cluster. With each UniBoard2 handling 1 Tera bits per second (Tbps), only 4 boards are needed to handle the full data stream of 3.8 Tbps. UniBoard2 will preprocess data for fast transient search in parallel to ongoing imaging observations.
With the UniBoard2s installed at the WSRT, ARTS is a step further to completion.
© ASTRON
The advent of exa-scale next generation radio telescopes poses challenges in data handling, requiring data to be processed quasi-realtime. Traditional pixel-based imaging algorithms such as CLEAN are not easily scalable to very large images especially when combined with high spatial resolution requirements. Also the processing load for traditional techniques becomes an issue. A related challenge is that radio astronomy imaging in most cases is an ill-posed problem, meaning that a single unique solution is not guaranteed.
To tackle this, dr Naghibzadeh applied several regularization approaches, and split the field of view into several regions for different source densities. Using efficient iterative inversion methods, including the so-called Krylov subspaces (a concept introduced in 1931), it was shown that the new approach (PRIFIRA) is computationally less demanding than traditional pixel-based approaches, and a good candidate for the snapshot imaging pipeline of the next generation radio telescopes.
This is not the end of this line of research, indeed, further testing on large data sets and joint calibration and imaging studies with PRIFIRA are logical next steps. But that is to be defined in the context of a new project.
© ASTRON Mechanical Department
For this particular scale model, 768 (!) photo-etched 0.2mm nickel-silver alloy parts have been used, to create a realistic impression of an SKA LFAA station from a birds-eye perspective.
With a personal interest for scale modeling, it was a great pleasure to build such a detailed model within the ASTRON mechanical department. The inscription on the model text plate writes:
A Low Frequency Aperture Array station of 256 SKALA4 antennas. The LFAA of SKA1-Low will host 512 of such stations, each covering a 35 meter diameter, in which the antennas will be deployed in a semi-random configuration.
© J Hargreaves, P Donker
Numerous hazardous re-orderings, transposes, re-quantizations, beamformings and channelizations await.
In order to ensure that all the signals are delivered safely into the expert hands of astronomers, the Desp firmware team has begun developing a suite of end-to-end tests. Each element in the array
can be replaced by a sine-wave generator, programmable in amplitude and frequency. For ARTS Science Case 4, we can connect each element to its own 'single-element' compound beam. Then we
sweep the sinusoid through the entire frequency band, switch to the next element and repeat until the signal has been applied to all forty compound beams. Some early results are shown here.
It is important that the signal shows up only on the Arts cluster node allocated to that compound beam, and nowhere else. We are developing scripts to check this automatically. Note
the expected gaps in the 'limited-bandwidth' compound beam, cb3: a built-in test of the test!
Further tests will include fine-grained frequency sweeps to measure the channelizer bin characteristics, and amplitude sweeps to check the quantization and saturation levels.
© JIVE
"The Americans wondered if I knew what the acronym meant", says Richard Schilizzi, one of the founding members and the first director of JIVE, "but the name stood out in a forest of European institutes named with an E." Since its inception, JIVE has become a global name for VLBI in Europe and beyond, and the institute is a key player in technological and scientific development of VLBI.
The core business of JIVE has always been to correlate and support EVN observations. The first correlator was completed in 1998, when data was still shipped on big tapes. Increasing computing capacity enabled the development of a software correlator, and eventually real-time data transfer via the internet (e-VLBI).
A major asset of JIVE is its support staff. They provide help during stages of an EVN observation, from proposal preparation to data analysis, and are at the core of EVN operations. After honing their VLBI skills at JIVE, they often continue their careers abroad, spreading the knowledge of VLBI and the JIVE brand around the globe.
Confident in its strong legacy, and with 25 years of experience in uniting European and global radio telescopes, JIVE is ready for a long and prosperous future.
© ASTRON
© Laura Driessen
The Crab pulsar is known for its rich possibilities of studies based on its pulse profile features: both giant pulses and individual pulses can be detected, and the changing shape of the integrated profile allow for studies of the interstellar medium (ISM) and the properties of the Crab nebula itself. Shortly after the discovery of the Crab pulsar, variability in scatter-broadening was already presented, and several periods of anomalous increases in scattering, as well as traceable additional features in the pulse profile have been published before. When another anomalous scattering event was detected in 2012 by the Jodrell Bank 42-ft Crab Monitoring campaign at 600 MHz, we decided to start to observe the Crab pulsar regularly with WSRT at 350MHz to study if the features were more clearly visible (ISM effects scale inversely with frequency, so the effects are expected to be more pronounced at lower frequencies).
In 2014, ASTRON summer student Laura Driessen analysed the available data and discovered that indeed the 350MHz band was the sweet spot for observing the ISM effects on the Crab pulsar. Contrary to what was thought before, the events did not happen every few years, but are present almost continuously. The figure shows the broad range of features, that can all be attributed to effects of changes in the path of propagation. We discovered that the commonly-used thin-screen model cannot be applied to all effects shown, and that the variations can happen on a fast timescales of less than a day.
The paper, which presents three years of data, has now been published in MNRAS.
© ASTRON
We are here with the ASTRON booth and all the necessary information the AAS visitors need about Lofar, SKA, Apertif, Aeneas2020, ADASS 2019 and of course our Summer Student Programme and our Traineeship. We also participate in the AAS Outreach programme on Wednesday, when schoolchildren will visit various booths to learn about astronomy. We will show them how an interferometer works.
We enthusiastically introduce our American colleagues to the world of European (and Dutch) radio astronomy.
© Ronald Halfwerk
The project closed its activities with a scientific conference organised in Jurmala, Latvia on December 5. Attendees from Latvia, Ukraine, Russia, Bulgaria, Germany, France, the United Kingdom and the Netherlands collectively shared the knowledge and experience gained during the project.
The conference was followed by a Workshop at the Irbene Observatory of VIRAC on December 6, with the goal of promoting the opportunities that the participation of VIRAC in LOFAR and the EVN will bring to the new user community, and to intensify links with partner scientific and technological institutes in the wider European region. The workshop covered topics from the basics of ILT science operations, organization and future upgrade, to science research topics from potential users.
VIRAC expressed its pleasure and gratitude with the results they derived from the BALTICS project. The impression of the ASTRON participants is that we significantly contributed to increasing their capabilities. Furthermore, we were impressed by the work of all contributors in their research in Low Frequency Radio astronomy and the related technical facilities. We were excited to see the ground preparations for the LOFAR station, and we look forward to welcoming the Latvian consortium as ILT partner in 2019.
© ASTRON
As you can see, even after a fully loaded year, everybody is still smiling at the end of 2018 in sight. To be frank: the real reason of these smiles was caused by a bottle of water, which I accidentally toppled when finding the best shot.
© Open access
© Astron Mechanical Group
A. Blunt needle with a combination of UV light, syringe, milk, food colorings, water, high temperature, 2 engineers, one research instrument maker and an intern in a mechanical workshop INDEED resulted in a big mess. We did clean afterwards, no traces of mess to be seen .... However, that is not the proper answer of a line manager
B. It was a weird experiment, but heck, that is what the Mechanical Department is for - to THINK OUTSIDE THE BOX and perform weird experiments and achieve great results!
We NEVER ever scare or tease anybody.... Seriously, never ;-) at least not the interns. What about the blunt needle? In this particular experiment, we really had to use the blunt needle to inject the UV marker, food colorings, and at the end a whole syringe of milk to the system... It was an intricate operation, but I will assure you that our patient has survived and we got to know more about its 'ins and outs'. Nobody was hurt but a hose, which was bleeding (red colored) water by the way. However, this was NOT the answer of the manager either.
C. We did have fun. We do have fun every day because our work is FUN. Everybody who works in the Mech. Department has a screw loose here and there. Well, you need to if you are so happy solving puzzles day in and day out. Apparently loosing one's screws is contagious because even Gijs caught the bug of enthusiasm from the mechanical groupies:))and drunk some of the red food coloring. Nothing special, no taste to it (only the coloring was slightly too old [sic!]). NOPE, C was not the answer of the line manager.
D. Abstract... YES that is the solution to the mechanical riddle! The heat sink worked so well (first time right, right?!) that it needed some paperwork as a follow up. At that time when the experiment took place: no, no abstract had been written yet.
If it still sounds too mysterious to comprehend: we created a setup to visualise the FLOW of coolant across the Gemini LRU liquid cooling heat sink. The objectives were to find areas that needed optimisation, to eliminate the dead corners and enhance the performance of the heat sink. Mission status: accomplished, 2nd generation Heat Sink should have the optimised geometry for the abstract.
© APERTIF room team
In the past year the team members have enjoyed each other's company and we think we got to know each other rather well. To memorise the split up of the team, we had to have some kind of a goodbye event. At the end of each year it is time for all kinds of lists, so we decided that each of us would make a personal musical top 3 which would be combined in a single list. This AJDI shows the resulting list (in alphabetical order).
We played this playlist at the last joint working day of 2018. To test how well we
know each other, we had to guess who submitted which song. The result was not bad at all; almost 40% was guessed correctly. The most amazing result was that Mieke, who joined the team only quite recently, guessed best with almost 50%. Ger was the best known (or probably most predictable) person; almost
75% of his songs were guessed correctly.
It was a nice and fun event. We leave it as an exercise to the reader to guess our musical preferences.
© CC-BY-4.0 Tammo Jan Dijkema
© ESA
© ASTRON
Ten years ago, Henk Vosmeijer built a webform to replace this "verlofbriefje". Over the years he added extra functionalities until what it is now.
Now we are 10 years and 120.000+ requests later and still going strong.
© ASTRON Mechanical Department
ASTRON, ISIS and Radboud University developed the NCLE antenna and instrument, with which the satellite is equipped. Earlier this year, our colleagues witnessed the launch of the CNSA rocket at the Xichang Space Center.
This unique Dutch collaboration with the Chinese Space Agency and The Chinese Academy of Sciences (CAS-NAOC) begged for a proper trophy at ASTRON. Therefore, since Christmas, the presentation showcases at the entrance hall are supplemented with an explanatory and educational 1:10 scale model of the Chang'e-4 relay satellite with the NCLE instrument and antenna highlighted in blue.
© Thomas Tijsma / Tammo Jan Dijkema
As an intern at ASTRON, I took it upon myself to solve this issue with an algorithm and started by looking at similar graph problems for both inspiration, and perhaps an easy solution. The most related graph problem is the Steiner tree problem. A Steiner tree is an extension to a minimum spanning tree, where so called “Steiner points” are added to minimize the the total distance. Unfortunately no implementation is available that meets all the specific requirements necessary to solve the issue at hand.
So I designed a problem specific algorithm, along with approximately twenty template layouts. The algorithm will measure the cost of combining the input matched with a template, for all templates. The cost is based on the cost of cable length (only 85 meter or 115 meter cables are used) and the total amount of digging done. The best combination will be given as result.
After this process the best result will be tidied up by the algorithm to meet certain demands that are important for the quality of the LOFAR field.
For several LOFAR fields not in the template solutions, the algorithm I implemented produces better results than manually generated ones. The cable layout code now lives on Github and may be used for future international LOFAR fields.
© Photo: Cees Bassa (ASTRON)
I would mostly like to thank all the ASTRON and JIVE colleagues who helped host Astrolunch when I was away, as well as thanking the hundreds of great speakers we've had. Astrolunch is a great opportunity to hear about cutting-edge science and to discuss with a friendly and lively group.
© ASTRON
