Articles on this Page
- 12/16/18--16:00: _UniBoard2 ready for...
- 12/19/18--16:00: _PhD Defence Shahrza...
- 12/18/18--16:00: _SKA LFAA scale model
- 12/17/18--16:00: _End-to-end Testing ...
- 12/20/18--16:00: _25th anniversary of...
- 12/23/18--16:00: _ASTRON Season's Gre...
- 01/01/19--16:00: _ASTRON News Winter ...
- 01/06/19--16:00: _Scattering features...
- 01/07/19--16:00: _ASTRON at AAS 233
- 01/08/19--16:00: _BALTICS final Confe...
- 01/09/19--16:00: _Last DESP Project P...
- 01/10/19--16:00: _LOFAR Minecraft - L...
- 01/13/19--16:00: _Behind the Scenes: ...
- 01/14/19--16:00: _Knowing the APERTIF...
- 12/16/18--16:00: UniBoard2 ready for ARTS
- 12/19/18--16:00: PhD Defence Shahrzad Naghibzadeh
- 12/18/18--16:00: SKA LFAA scale model
- 12/17/18--16:00: End-to-end Testing of the ARTS Firmware
- 12/20/18--16:00: 25th anniversary of JIVE
- 12/23/18--16:00: ASTRON Season's Greetings
- 01/01/19--16:00: ASTRON News Winter edition
- 01/06/19--16:00: Scattering features and variability in the Crab pulsar
- 01/07/19--16:00: ASTRON at AAS 233
- 01/08/19--16:00: BALTICS final Conference and Workshop
- 01/09/19--16:00: Last DESP Project Progress Meeting of 2018
- 01/10/19--16:00: LOFAR Minecraft - LOFAR Enters the Virtual Universe
- 01/13/19--16:00: Behind the Scenes: Mechanical Riddle solution
- 01/14/19--16:00: Knowing the APERTIF room team
© ASTRONHalf November four UniBoard2 have been installed at the Westerbork telescope for the Apertif Radio Transient System (ARTS). Together (Jan-Pieter de Reijer, Sieds Damstra and the submitter) we have installed the boards in a cabinet and connected the power, control signals and cooling. After years of prototyping it is the first operational liquid cooled processing platform for ASTRON. The heat from the FPGA is directly transferred from the FPGA towards the outside of the building, bypassing the power consuming air conditioning inside the HF-cabin.
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.
© ASTRONOn Friday December 7th, Shahrzad Naghibzadeh successfully defended her PhD thesis Image Formation for Future Radio Telescopes at TUDelft. Starting in 2014, Dr Naghibzadeh started her work on image formation in the NWO BBBD DRIFT project at TUDelft. This was conducted in the context of the ASTRON-IBM DOME project, and supported by the Province of Drenthe and the Ministry of Economic Affairs.
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 DepartmentIn November we updated the central hall general presentation showcase with a new scale model of a 1:87 scale SKA LFAA station. In an attempt to offer visitors a clearer understanding of completed, current and future projects that ASTRON is working on, supporting demonstration demos and/or models have proven to be a meaningful addition.
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 DonkerSignals collected by the WSRT Apertif phased array feed may have finished their journey across the Universe, but they are about to begin a far more perilous voyage through the ARTS/Apertif firmware.
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.
© JIVEThe technique of Very Long Baseline Interferometry (VLBI) was not even 25 years old when it became clear that there was room for a dedicated operational institute to streamline VLBI efforts in Europe. The European VLBI Network (EVN) was becoming a globally leading endeavour, and needed a central institute where data could be correlated, and scientists could receive assistance with data processing and analysis. After several years of discussions and negotiations, this vision became a reality: the Joint Institute for VLBI in Europe (JIVE) was formally founded on 21 December 1993, and hosted in Dwingeloo at the location of ASTRON.
"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.
© ASTRONOn behalf of our Board, Management Team and all of our staff, we wish you a Merry Christmas and a Happy New Year! We are looking forward to�a great 2019!
© ASTRONIn case you missed it. The Winter edition of the ASTRON News is now available. You can read the latest edition: here
A PDF version is available: here
© Laura DriessenWe have studied the pulsar profile of the Crab pulsar at 350MHz using WSRT data from 2012 to 2015. We found that besides variable scatter-broadening of the profile, additional features due to multi-path propagation effects in the interstellar medium or Crab nebula can be detected in almost all observations.
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.
© ASTRONFrom 6 - 10 January ASTRON is at the American Astronomical Society (AAS) Winter Meeting in Seattle, WA.
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 HalfwerkBALTICS is a H2020 twinning project running between January 2016 and December 2018. The partners are VIRAC (Ventspils International Radio Astronomy Center), ASTRON, and University of Manchester (UMAN). BALTICS aims at strengthening the expertise and experience at VIRAC in the field of radio astronomy research as well as technology and instrumentation. The project enables intensive contacts with two internationally leading research institutions (ASTRON and UMAN), focused on LOFAR, eMERLIN, and VLBI techniques. It comprises development and training in instrumentation and data analysis, accompanied by dissemination and scientific publications.
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.
© ASTRONEvery Tuesday we organize DESP project progress meetings wherein we discuss the progress of running development projects, focusing on the firmware and hardware design work. In just 30 minutes, all projects we are involved in are discussed. The meetings are held in Andre's room, which is efficiently used by the use of crutches to crank as many persons as possible in one room.
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 accessFionn (11) and Luke (8) Teeling-Gallagher, son's of the I-LOFAR PI, have been busy constructing an international LOFAR station in Minecraft. Listen to a full description in their YouTube movie at https://youtu.be/AVqLDZ-Kwzk
© Astron Mechanical GroupIt took some time [sic!], but to those of you who have been bothering the Boss of the Mechanical Group about the solution to the Mechanical Riddle, here it is:
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 teamThe core team (Agnes, Boudewijn, Eric, Ger, Marcel, Menno and Mieke) in the APERTIF room has been around for quite a long time and enjoyed working together so closely. At the start of 2019 this team will cease to exist; some will be moved to another room and continue to work on Apertif, some others will start working on LOFAR-2.0 and maybe stay in the (what will then be called) LOFAR room.
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.