Pulsars/Westerbork on VPRO's Labyrint

December 16, 2013, 4:00 pm

≫ Next: Low Noise Tile project, first frontend results

≪ Previous: Bonn-Dwingeloo Neighbourhood Meeting 2013, Bonn

On Sunday 8 December the science program of VPRO, Labyrint, broadcast an episode on "Time", featuring pulsar research with Westerbork.

In the 25-minute overview, our understanding of time is discussed, demonstrated, and even illustrated mid-air (as seen in the picture, above) by 5 experts: three (astro)physicists, including ASTRON's Joeri van Leeuwen, highlight the fundamental space-time perspective, while two experimental psychologists explain the human perception of time.

The program is about 80% Dutch-spoken, with some English. It features quite a few nice shots of Westerbork, and some good, new pulsar animations. The show is available online at uitzendinggemist.nl.

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Low Noise Tile project, first frontend results

December 17, 2013, 4:00 pm

≫ Next: 1993-2013: 20 years of supporting VLBI in Europe

≪ Previous: Pulsars/Westerbork on VPRO's Labyrint

The Low Noise Tile (LNT) project is an internal research project with the aim of making a phased array tile with a very low noise temperature. The work is a continuation of work which was presented in the AJDI of 6-8-2010. The LNT tile uses an APERTIF tile as basis, but with a completely new designed frontend, suitable for achieving very low noise temperatures. With frontend we mean a whole chain of Low Noise Amplifiers, filters, limiters and buffer amplifiers and more filters to keep the frontend linear, and noise limited by the first stage the Low Noise Amplifier. In this case the first LNA is a Skyworks LNA. This LNA is being advertised as a very low noise amplifier with a noise temperature of 25K, so let's see if its meets its specifications in a real aperture array system.

This daily image shows the potential of the LNT frontend. The noise is compared to a connectorized APERTIF frontend made in 2012.

The graphs show the measured NT and gain of both frontends as measured using an Agilent noise figure meter. The noise temperature improved by 10K from 45K for the Apertif frontend to 35K for the LNT fronted. The latter is designed to have 50dB of gain instead of the 42dB for Apertif.

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1993-2013: 20 years of supporting VLBI in Europe

December 18, 2013, 4:00 pm

≫ Next: 1993-2013: 20 years of supporting VLBI in Europe

≪ Previous: Low Noise Tile project, first frontend results

On 21 December 2013, JIVE celebrates the 20th anniversary of its foundation. JIVE began life as an institute with a very small group of people under the leadership of Professor Richard Schilizzi. Our mission was to build and operate the Mark IV hardware correlator for the European VLBI Network. JIVE has grown significantly in the past two decades, and the EVN and JIVE have always been on the frontiers of VLBI research and technology. Magnetic tapes have been replaced by disc packs, recording rates have increased from 128 Mbps to 1024 Mbps, and real-time correlation via e-VLBI has emerged as a standard EVN operation mode for e-EVN sessions. JIVE also played an important role in the tracking of the Huygens probe as it descended through the thick atmosphere of Titan all the way and down to the surface. These efforts directly resulted in the later development of the EVN software correlator at JIVE (SFXC) we are using today for correlation of European VLBI Network data.

Ever optimistic and enthousiastic, JIVE employees are looking forward to an equally bright future, as JIVE is expected to become an European Research Infrastructure Consortium (ERIC) in 2014.

Over the 20 long years, many people actively contributed to the success of JIVE. Some are no longer in Dwingeloo, but their highly dedicated work is also remembered.

Prof. Huib Jan van Langevelde

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1993-2013: 20 years of supporting VLBI in Europe

December 20, 2013, 4:00 pm

≫ Next: The LOFAR core, on your desktop

≪ Previous: 1993-2013: 20 years of supporting VLBI in Europe

Ever optimistic and enthousiastic, JIVE employees are looking forward to an equally bright future, as JIVE is expected to become an European Research Infrastructure Consortium (ERIC) in 2014.

Over the 20 long years, many people actively contributed to the success of JIVE. Some are no longer in Dwingeloo, but their highly dedicated work is also remembered.

Prof. Huib Jan van Langevelde

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The LOFAR core, on your desktop

December 19, 2013, 4:00 pm

≫ Next: X-rays from the state-changing PSR J1023+0038

≪ Previous: 1993-2013: 20 years of supporting VLBI in Europe

Pick a random astronomer, and they're likely to be carrying a Mac laptop. With the newly released upgrade (called Mavericks) to the operating system, there is now a map-browsing application built in. Of course the first thing a LOFAR aficionado might do is zoom in to the Exloo area! As in bing, the core area looks great. Now you don't have to remember how to get there in your web browser ...

Also check out WSRT, where you can easily tell which of the antennas has been used for the Digestif system.

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X-rays from the state-changing PSR J1023+0038

December 22, 2013, 4:00 pm

≫ Next: Sinterklaas had gifts for LOFAR too on 5 December

≪ Previous: The LOFAR core, on your desktop

The pulsar PSR J1023+0038 is doing something peculiar: in June it disappeared as a pulsar and lit up in gamma rays. Unfortunately at the time it was too close to the Sun to observe with major optical telescopes or space-based X-ray telescopes. In October, though, as soon as it became possible, we observed the pulsar with the Swift X-ray telescope to try to determine what had happened.

What we found was that the X-rays and ultraviolet had gotten much brighter. We think what happened was that the system, which contains a pulsar and a slightly distorted main-sequence star in a very close orbit, formed an accretion disc: material is overflowing from the main-sequence star and falling towards the pulsar and growing extremely hot in the process. This hot material blazes in the ultraviolet and even the X-rays.

The image shows a still-mysterious aspect of the X-ray data: although the X-rays are generally bright, once in a while the X-ray flux drops down to the very limit of detectability for a few minutes at a time. It's not clear what could cause these short dropouts. A few minutes is roughly how long it should take to refill the inner hundred kilometers or so of the disc, so perhaps when the flow is weaker than usual the pulsar can turn on for a little while, clearing out the inner part of the disc?

This picture is drawn from Patruno et al. 2013. We announced the pulsar's disappearance in Stappers et al. 2013, and described its behaviour when it doesn't have an accretion disc in Archibald et al. 2013. We are carrying out a multiwavelength observing campaign to clarify what is happening in this puzzling system.

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Sinterklaas had gifts for LOFAR too on 5 December

December 23, 2013, 4:00 pm

≫ Next: Season's Greetings from ASTRON

≪ Previous: X-rays from the state-changing PSR J1023+0038

There is many centuries old tradition in the Low Countries centred around giving presents on the eve of Saint Nicolas day, December 5th. It is one of a few traditions that is Roman-Catholic in origin that survived the Protestant Reformation in the traditionally Calvinist Netherlands. Nowadays the holiday is often referred to by St. Nicolas nickname: Sinterklaas. Sinterklaas celebrations entail giving nicely wrapped presents often accompanied by some small written poem. According to the mythology the presents have been delivered by Sinterklaas on his horse riding the rooftops. This year he had to brave a fierce storm.

When arriving in the morning of December 6th at the Donald Smits Center for Information Technology (CIT) there were some nicely wrapped packages delivered the day before. Given the date, this obviously must have been the doing of Sinterklaas. The packages contain the servers and other hardware for what is going to be the CEP (CEntral Processing) III cluster, primarily the successor of the now ageing CEP I hardware. This cluster will have several purposes, but mainly it will be used for developing LOFAR software, algorithms and pipelines and manual processing of LOFAR data. The CEP II cluster will continue as the main cluster for automated processing. More news on CEP III will follow after the holidays.

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Season's Greetings from ASTRON

December 24, 2013, 4:00 pm

≫ Next: Seating Patterns II

≪ Previous: Sinterklaas had gifts for LOFAR too on 5 December

We wish you all a merry Christmas and a prosperous 2013!

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Seating Patterns II

January 2, 2014, 4:00 pm

≫ Next: Getting in the Mood for 2014

≪ Previous: Season's Greetings from ASTRON

This is the second picture in our series about spontaneous seating patterns in the new auditorium. This group consists of three "year-clubs" (1965/66/67) of a locally prestigious strand within the oldest (and eldest) Delft fraternity. It is possible that their curious seating pattern(*) is the result of a time-honoured pecking order that is difficult to explain to outsiders.

In any case, this gathering of ingenieurs near the end of their varied orbits was very impressed with ASTRON, JIVE and DOME. In fact, they wondered why they knew so little about the achievements of these cutting-edge organizations. Apart from manfully blaming themselves for being too preoccupied with other things, they concluded that our kind of work is not easily done justice by the breathless sound effects and oneliners that seem to be the norm in these hectic times. Fortunately, our Maecenas in Brussels, and our Royal Family, know better.

(*) The seating pattern is all the curiouser since the speaker is located near the camera.

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Getting in the Mood for 2014

January 1, 2014, 4:00 pm

≫ Next: Pulsar with two white dwarf companions promises to test theories of gravity

≪ Previous: Seating Patterns II

One rather compelling theory of dreams holds that they are the result of white noise, filtered by our highly personal reference frame of prejudices and preconceptions.

This recent image of the evolving plain in front of the venerable Dwingeloo telescope is not white noise, of course. But it contains enough features to be subjectively filtered by a pensive mind.

From the editors of the ASTRON/JIVE Daily Image: May your glass be at least half full in 2014.

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Pulsar with two white dwarf companions promises to test theories of gravity

January 6, 2014, 4:00 pm

≫ Next: Thijs Coenen awarded PhD for thesis "Searching for pulsars with LOFAR"

≪ Previous: Getting in the Mood for 2014

Using the Green Bank Telescope, we have discovered a new fast-spinning pulsar that is unique: it is closely orbited by one white dwarf, and more distantly orbited by a second. We have measured the complex interactions of these three bodies in an intensive campaign of timing observations with the Arecibo observatory, with the Green Bank telescope, and - taking almost daily observations - with the Westerbork Synthesis Radio Telescope. Fitting theoretical models to these data has allowed us to almost completely determine the geometry of the system (see image, or video) and obtain very precise measurements of the masses of the stars: in particular, the pulsar mass is 1.4378 ± 0.0013 solar masses. We plan to use our measurements of this system to test theories of gravity.

Einstein's theory of gravity is based on the Strong Equivalence Principle, which predicts that objects should fall the same way no matter how compact they are. Almost all other theories of gravity predict that very compact objects should begin to deviate. In this new system, we have the extremely compact pulsar and the less compact inner white dwarf falling in the gravity of the outer white dwarf. If they fall differently, we should see it in our measurements. If they fall in exactly the same way, then theorists will need more ingenuity to come up with new theories of gravity that can match Einstein's in this orbiting laboratory.

The discovery and timing of this new system are described in Ransom et al. 2014 (arXiv version).

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Thijs Coenen awarded PhD for thesis "Searching for pulsars with LOFAR"

January 5, 2014, 4:00 pm

≫ Next: Observation of HI absorption line by APERTIF UniBoard

≪ Previous: Pulsar with two white dwarf companions promises to test theories of gravity

On November 20, 2013, Thijs Coenen obtained his doctorate with a dissertation on the LOFAR pulsar searches. At the ceremonial defense, in the Agnietenkapel in Amsterdam, Thijs engaged in a discussion with, and was able to parry questions from, a committee including such formidable opposition as Profs. dr. Morganti, Van Den Heuvel, Hermsen and Wijers. Based on the thesis and the defense, the committee was then pleased to award Coenen the doctorate. Promotor Van der Klis next admitted Thijs to the degree of doctor of philosophy, and co-promotores Van Leeuwen and Hessels were the first to praise and congratulate the new doctor.

The main thrust of the thesis is the search for radio pulsars using LOFAR; it also describes extensions to standard single-pulse search techniques and two smaller search projects. As part of LOFAR's commissioning Thijs and the Pulsar Working Group performed two radio pulsar surveys, the LOFAR Pilot Pulsar Survey (LPPS) and the LOFAR Tied-Array Survey (LOTAS). The former survey put a limit on the fast radio transient rate and re-detected 65 pulsars, while the latter re-detected 27 pulsars and discovered 2 new ones! These discoveries bode well for future, more sensitive, pulsar surveys using LOFAR.

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Observation of HI absorption line by APERTIF UniBoard

January 7, 2014, 4:00 pm

≫ Next: LOFAR Honey

≪ Previous: Thijs Coenen awarded PhD for thesis "Searching for pulsars with LOFAR"

We proudly present the first observation of an HI absorption line detected by the APERTIF system with a UniBoard backend!

The (nearly) final APERTIF hardware, as it was used to do the first APERTIF UniBoard pulsar detection a few weeks ago, has now also been used to observe this spectral line feature of the bright radio source 3C84 (NGC 1275). 3C84 is a strong radio continuum source, but a cloud of HI gas in between the source and the telescope absorbs the emission from 3C 84 in a narrow band. This shows up in the measured data as an absorption line at 1382.97 MHz.

The 2 MHz frequency band shown here is a combination of three sub-bands, each 0.78125 MHz wide. The sub-band filter responses were removed from the data by means position switching, in which the observation is done twice, i.e. on-source and off-source. The total observation time is ~9 hours. The figure represents the ratio of both measurements, and shows no sub-band filter responses at all - resulting in this nice spectrum of 3C84!

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LOFAR Honey

January 8, 2014, 4:00 pm

≫ Next: A New Broom presents himself

≪ Previous: Observation of HI absorption line by APERTIF UniBoard

Editor's note: This image eloquently speaks for itself, so it does not need a blurb. Except perhaps to note that our British friends have a rather endearing tendency to ignore the other 97.5% of LOFAR. But the most important thing is that members of the extended LOFAR family keenly follow the ASTRON/JIVE Daily Image, and take the trouble to contribute interesting (and amusing) images from time to time. We love you all.

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A New Broom presents himself

January 9, 2014, 4:00 pm

≫ Next: Apertif DCU sub-rack

≪ Previous: LOFAR Honey

In early December, the Board of NWO visited Astron and had incisive discussions with Astron board and staff. This was an excellent opportunity for Dr Ir Gert Kruithof, the new Head of Research and Development, to present the latest innovations from the R&D laboratory, and himself. Gert has a PhD in Applied Physics from Groningen University, and has made his career in the highly regarded Dutch Institute for Applied Physiscs Research (TNO). Most recently he led the TNO division of ICT Business Information Services.

The NWO Board members showed a keen interest in our developments on phased-array feeds, photonic beamforming, a water-cooled Uniboard for digital signal processing, and High-Performance Computing. These innovations are extremely important for LOFAR, APERTIF and SKA. In addition, the path to valorization of these technologies for domains other than radio astronomy was highlighted.

Gert is the first outsider to be appointed in this function, and that seems to be working out remarkably well. Since he has only been the head of Astron R&D since August, he was obviously showing the fruits of developments that were set in motion by his predecessors. He is keenly aware that he stands on the shoulders of giants(*).

But the times have changed (as even dinosaurs realize), so the Astron R&D lab will increasingly have to operate in a rather different environment. The main challenges are the new partnership with a greatly expanded Astron astronomy group that now has its own sources of funding, and securing a substantial role within the context of the worldwide SKA movement. Gert has recently laid out his plans to the R&D staff, and looks forward to meeting the new challenges together with this remarkable group of specialists. (A small but representative sample can be seen loitering in the background of the picture).

(*) Lex Muller, Jean Casse, Wim Brouw, Arnold van Ardenne, Marco de Vos, and the Triumvirate led by Albert-Jan Boonstra. (Wim Brouw is included because he led the computing effort before it became part of R&D after the re-organisation of 1990).

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Apertif DCU sub-rack

January 12, 2014, 4:00 pm

≫ Next: "If you want to predict the Future, you will have to invent it"

≪ Previous: A New Broom presents himself

Displayed is the down-converter sub-rack of Apertif in its present state. The main purpose of the subrack is to perform frequency translation of the 32 inputs, from the desired RF frequency range to the 300 MHz input bandwidth of the A/D-converter.

The design of this sub-rack started as a derivative of the receiver sub-rack for AAVS and EMMA. Mechanically it is still roughly the same. However from an electronics perspective, due to the ever increasing requirements, the design has significantly changed since then.

The sub-rack consists of four types of modules:

First and foremost is the DownConverter Unit (DCU), which performs the actual frequency translation. It also incorporates amplification, filtering, local oscillator distribution as well as gain control.

A splitter module is used for distribution of both local oscillator signals.

The power module is used to connect the external power supply to the backplane.

Finally the control module takes care of all control signals in the subrack, as well as local power supply and temperature monitoring. Communication is performed over ethernet.

Currently the design of the backplane, splitter-module, power-module and control-module hardware has finished. The design of the DCU is still ongoing. It is expected to have enough prototype hardware ready in the second half of March, to build three sub-racks. These subracks will then be used for the Alpha-3 testing of Apertif.

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"If you want to predict the Future, you will have to invent it"

January 13, 2014, 4:00 pm

≫ Next: Four new participants DOME Users Platform

≪ Previous: Apertif DCU sub-rack

Yesterday, the ASTRON/JIVE/NOVA/DOME community was treated to the traditional New Year's speech by ASTRON Director Mike Garrett (the JIVE Director has already strutted his stuff at the Christmas High Tea Ceremony). As such speeches go, this year's was a good one. We reward him here by using one of his favourite pictures.

Mike started with a few stories about the people he had talked to during his regular Christmas stroll around the building. Of course he was very impressed with their diligence and inventiveness, but he had also listened carefully to their concerns. For instance the publication pressure on the technical and science support staff, who have some major instruments to deliver and operate. He also praised the unassuming but essential labours of services like ICT, FZ and HRM, who measure their success by their invisibility. He even had some kind words for the invaluable contributions of the small herd of dinosaurs.

On the whole, the speech emphasized ASTRON again as a major institute for astronomical instrumentation. Mike highlighted the importance of JIVE, NOVA and DOME, the sister institutes hosted by ASTRON, that complement it in many ways (even though the mutual synergy could still improve in some areas). He even hinted at the possibility of a largish new VLBI dish, in the context of the emerging African VLBI Network (AVN).

Of course SKA will have a Big Impact in the coming years, in many different ways. Nevertheless, Mike is very much aware of the danger that the emergence of such a huge instrument can destroy the community that built it. Fortunately, the operation of SKA will generate new opportunities, e.g. regional SKA data centres. In addition, a large new instrument can only fullfil its mission if the builders are prepared to upgrade it over the years. The WSRT/APERTIF and EMBRACE projects can be seen in that light, and there should be a trail-blazing role for an evolving LOFAR even when SKA exists.

As the title suggests, the best way to be influential is by the convincing demonstration of new technology. ASTRON has been an early adopter of phased arrays and focal plane arrays, and the success of LOFAR has greatly influenced the acceptance of aperture arrays for SKA. ASTRON is well placed to play a leading role in the logical process to extend this to higher frequencies, up to 1.5 GHz.

People were riveted to their seats and left with a spring in their step.

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Four new participants DOME Users Platform

January 14, 2014, 4:00 pm

≫ Next: 4th NL SKA Industry Information meeting

≪ Previous: "If you want to predict the Future, you will have to invent it"

Today, Wednesday 15 January 2014, project DOME has reached another milestone. Four more parties are officially joining the DOME Users Platform: KxA (previously known as Dysi-SI), Transfer-DSW, RUG-CIT and the Netherlands eScience Centre.

Productive partnership. As of today, these four companies and knowledge institutes are official partners, as formulated in separate DOME Users Platform collaboration agreements. They are now active participants in project DOME and catalysts for valorization of the scientific insights and technological breakthroughs DOME will yield.

Good company. Before the documents are signed, Albert-Jan Boonstra (scientific director DOME for ASTRON) and Ton Engbersen (scientific director DOME for IBM) will give an update on the DOME and SKA projects. After that, representatives of all four parties will take part in a signing ceremony at ASTRON's Van de Hulst Auditorium, together with Alexander Brink (chairman of the DOME steering board) and Marco de Vos (ASTRON's managing director and DOME steering board member).

After lunch, each CEO or director will go into some detail concerning the activities they will undertake within the Users Platform. In order to maximize synergy, there will also be room to discuss the interaction between members of the Users Platform and DOME research teams.

About DOME: DOME is the project in which IBM and ASTRON have joined forces to create new technology for handling the deluge of data that will be generated by the Square Kilometre Array (SKA), the world’s largest and most sensitive radio telescope. DOME is one of the most data-intensive science projects ever. It requires and stimulates ground-breaking research, which will take aspects like computing speed and capacity, storage capacity and efficiency, pattern recognition and energy reduction to a completely new level.

We will keep you posted of any future developments around the DOME Users Platform.

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4th NL SKA Industry Information meeting

January 15, 2014, 4:00 pm

≫ Next: The Hendrik C. van de Hulst Auditorium

≪ Previous: Four new participants DOME Users Platform

Today, a long overdue, 4th NL SKA Industry Information meeting is being held in Dwingeloo. Representatives from Dutch companies interested in playing a role in the SKA will hear of project developments over the past two years. After a fairly quiet initial period in which the new SKA Organisation, based at Jodrell Bank Observatory near Manchester (UK) took up the leadership of the project, 2013 saw the allocation of work packages to (self funded) multinational consortia. ASTRON is leading two of these: the Low and Mid Frequency Aperture Array consortia. The institute is also heavily involved in the central processor- and science data processing consortia - supported largely by the DOME collaboration with IBM (see yesterday's Daily Image). There are many areas of overlap between SKA technology development and the various roadmaps that have been developed in recent years as part of the Dutch government's Top-Sector policy initiative.

The Square Kilometer Array is to be built in two phases in both Australia and South Africa. In Phase 1, hundreds of phased array antenna stations (with up to a quarter of a million antennas) similar to those used in LOFAR will be built in Australia. In parallel, 190 dishes in South Africa and 60 dishes equipped with phased array feeds will be built in Australia, incorporating the two precursors ASKAP and MeerKAT that are under construction now. In addition to these very visible parts of the SKA, significant investments in network and power infrastructure will be needed. Processing of the massive data streams will require state of the art digitial processing algorithms and hardware. The scale of these developments are such that they require an industrial approach. Opportunities for industry involvement, both in the design phase (2014-2016) as well as in the construction phase (2017-2023) will be discussed.

Apart from ASTRON speakers involved in various aspects of the SKA Project, the participants will also hear from commercial companies involved in previous and ongoing radio astronomy projects at ASTRON.

For further information, including a programme: http://www.astron.nl/general/nl-ska-industry-meeting/nl-ska-industry-meeting

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The Hendrik C. van de Hulst Auditorium

January 16, 2014, 4:00 pm

≫ Next: Discovery of Carbon Radio Recombination Lines in absorption towards Cygnus A

≪ Previous: 4th NL SKA Industry Information meeting

The new auditorium has been in use for almost a year now but it is only recently that the room was formally named in honour of Prof. Hendrik C. van de Hulst (1918-2000).

Henk was a young PhD student of Minnaert's in Utrecht during WWII, and came into contact with the Director of the Leiden Sterrewacht, Prof. Jan Oort, when he submitted a paper to a scientific essay competition. Oort immediately recognised the potential in the young man, and challenged him to investigate whether there might be a spectral line observable in the radio part of the e-m spectrum. Oort realised that such a line could be invaluable in mapping out the structure and dynamics of the Milky Way which was difficult to observe at optical wavelengths due to dust obscuration.

van de Hulst returned to Oort with the prediction that conditions in the ISM of our own and other galaxies might be suitable for the detection of the 21cm (1.4 GHz) hyperfine transition of neutral hydrogen (HI), the latter being just the most abundant element in the Universe! The rest, as they say is history - leading to the detection of HI at Kootwijk some 7 years later, and the completion of the construction of the 25-m Dwingeloo telescope in 1956. Henk was also a pioneer of the then emerging discipline of Space Science, and was instrumental in the set up of COSPAR and the establishment of our sister organisation SRON.

Even today, HI plays an important role in astrophysical research - indeed perhaps more so than ever before - not only does the study of HI in both emission and absorption form a major scientific case for telescopes such as the SKA (and its pathfinders e.g. WSRT-APERTIF, MeerKAT & ASKAP) but it is currently a major hot topic for LOFAR (and other low frequency radio telescopes) via studies of the Epoch of Reionisation.

The photo of Henk presented above is now hanging in the new auditorium. We'd like to think that he would take great interest and indeed not a little pride in the various discoveries that will be presented at colloquia and other events organised in the auditorium over the coming years.

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