50 years of VLBI!!

April 12, 2017, 5:00 pm

≫ Next: Girlsday 2017

This month the astronomy community is commemorating the 50th anniversary of the first successful VLBI (Very Long Baseline Interferometry) experiment. This was conducted in Canada on 17th April 1967, following many attempts in both Canada and the US, and theoretical proof of concept by Soviet Union authors. The successful experiment aimed to coordinate independent radio telescopes located 3074 kilometres apart, to focus on a single bright but compact radio source at exactly the same time. The Canadian team was headed up by Norman W. Broten and Alan Yen. Their detection of quasars on such a long baseline confirmed the compact nature of these radio sources, which were already at the time suspected to be associated with black holes. It took until 1995, and the combination of VLBI with optical spectroscopy to solidly confirm the presence of a supermassive black hole in the centre of galaxy NGC 4258.

Use of VLBI has increased the understanding of many astrophysical phenomena. It is also an essential tool for geodesy studies. This is only achieved because of the continued growth of VLBI technology, which has led to improved sensitivity and ever increasing quality (and quantity) of data collected during VLBI experiments.

Over the last decades, the Joint Institute for VLBI in Europe (JIVE) has played a key role in fostering this growth, through its dedicated support of the European VLBI Network (EVN), one of the leading global VLBI networks. JIVE and EVN are dedicated to the continued development of new technology to support the global astronomy community. In recognition of the hard work from all VLBI pioneers 50 years ago, we pay homage to the Canadian team and many others who opened up the VLBI door.

The image shows the 26-m telescope located at Dominion Radio Astrophysical Observatory, one of the original telescopes used in the first VLBI experiment. The second telescope at Algonquin Radio Observatory no longer exists.

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Girlsday 2017

April 13, 2017, 5:00 pm

≫ Next: VLBI: when people care about picoseconds, but can't remember the date

≪ Previous: 50 years of VLBI!!

It's that time of year again: Girlsday. Like in 2007, 2009, 2010, 2011, 2012, 2013, 2014, 2015 and 2016, a group of 32 girls from four highschools in the region invaded the building. Girls Day is a national initiative promoting STEM (Science, Technology, Engineering and Mathematics) to young girls aged 10-15 years.

The girls learned some programming in Minecraft, chatted with an astronomer, visited the Dwingeloo Telescope and soldered a badge which will flash 'LOFAR' when moved at exactly the right speed, and experimented with a 3d pen. This may be recognized as almost the same programme as in previous years. New however was the fresh enthousiasm of all the participating girls. We feel confident that these girl became a bit more enthousiastic about science and engineering today, and some of them might even be our future colleagues.

This Girls Day was organized by four institutes located around the Oude Hoogeveensedijk 4: ASTRON, JIVE, NOVA and CAMRAS.

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VLBI: when people care about picoseconds, but can't remember the date

April 16, 2017, 5:00 pm

≫ Next: Welcome to our new Director

≪ Previous: Girlsday 2017

According to the plaque in the image above, today marks the 50th anniversary of the first successful VLBI (Very Long Baseline Interferometry) experiment. This was conducted in Canada on 17th April 1967, where the 26-m dish at Dominion Radio Astrophysical Observatory (which bears the plaque) and a dish at Algonquin Radio Observatory were coordinated to observe a single bright, but compact radio source.

Tracing back the events makes it clear that the Canadian effort was the lucky one of many similar VLBI experiments taking place near simultaneously. There was a friendly rivalry between at least five teams, four in the US and one in Canada, and the cross-fertilization from this was essential to achieve success.

The year 1967 was densely packed with VLBI successes. In a paper reflecting on 30 years of VLBI, Jim Moran, from the US, lists several experiments in that year alone, though none on 17th April. Interestingly there are now slight inconsistencies in the recollections of the events. What is apparent is that at some point in the Spring fringes were detected - Norman Broten, from the Canadian team, recalls this happening on the 20th May, from observations recorded on 15th or 16th April, with a frantic effort to then present the work at URSI in Ottawa on 22nd May. By the time the Canadian experiments were published in Nature and Science, the US teams had reported several successful experiments as well.

It is no longer clear why 17th April 1967 was chosen to commemorate the first successful experiment in Canada. It is clear however, that this was a global effort that incorporated technical and theoretical contributions from many countries. In recognition of the hard work from the VLBI pioneers 50 years ago, we pay homage to all the teams who opened up the VLBI window on the Universe.

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Welcome to our new Director

April 17, 2017, 5:00 pm

≫ Next: This year's Cascade Run participants (well, most of them)

≪ Previous: VLBI: when people care about picoseconds, but can't remember the date

Today at 10:30, Carole Jackson, the new ASTRON Director, will be officially welcomed, and presented to all personnel of the four sister institutes in the Dwingeloo building: ASTRON, JIVE, NOVA and DOME. She will introduce herself to those she has not met already, and perhaps allow us a peek into the future.

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This year's Cascade Run participants (well, most of them)

April 18, 2017, 5:00 pm

≫ Next: Today's Colloquium: Magnetic fields in the multi-phase interstellar medium

≪ Previous: Welcome to our new Director

Three ASTRON teams participated in the 11th edition of the Hoogeveen Cascaderun, om April 9th 2017. Two teams of sporty enthusiasts did the 5 English mile distance, while one team of brave sportsmen and woman dared to challenge themselves with the 10 English mile distance.

With the friendly village of Hoogeveen packed with spectators, 8600+ runners were waiting excitedly for the start signal. The Sunday really honored its name by treating us to a cloudless blue sky and temperatures of well above 20 0C. It was a relief when the signal was finally given. Let's go!

All along the route there were spectators shouting their encouragements to the runners, bands and DJs playing, and choirs singing. There were even people sprinkling the runners using their garden hose; a very welcome cool-down for the many of us who suffered from the heat. From the point where the 5 and 10 mile routes joined again, we looped back to the center of Hoogeveen and prepared ourselves for a final sprint along its main shopping street. After a warm, if not overheated, welcome at the finish it was time for a well-deserved ice cream!

Well done everyone, and Cascaderun, see you next year!

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Today's Colloquium: Magnetic fields in the multi-phase interstellar medium

April 19, 2017, 5:00 pm

≫ Next: I-LOFAR skid frames halfway through production

≪ Previous: This year's Cascade Run participants (well, most of them)

Left: yellow lines show the observed radio polarisation angles of the galaxy M51, tracing out spiral magnetic-field lines that are ordered on the scale of the galaxy. Right: black lines show the mean magnetic field lines in a simulation of the interstellar medium, with the gas entropy shown in colour; the hot gas is yellow, the warm gas is red and the magnetic field prefers the latter. Today's colloquium will discuss and connect the observations and simulations.

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I-LOFAR skid frames halfway through production

April 20, 2017, 5:00 pm

≫ Next: Measuring UniBoard2

≪ Previous: Today's Colloquium: Magnetic fields in the multi-phase interstellar medium

It is cool to work at ASTRON as a mechanical engineer, because the assignments are so diverse. I am having fun solving engineering puzzles. They range from making fine parts/tools the size of 10x7 [mm] where a gap of 0.05 [mm] is already too big, to designing a 3x2.3x.1.9 [m] (WxLxH) pure steel 'heavy duty' transport frames. The latter ones are depicted in the picture above. Those skid frames have to fit on a taut trailer to bring the galvanized 3x3 [m] iron grids as cargo to romantic Birr Castle in Ireland where another beautiful LOFAR station is being built as we speak.

On my computer screen the size is relative. Everything seems so similar and is not so impressive because you just either zoom in or zoom out... Wait until you see the product in real life in production - only then it gets impressive.

Just then, when you see the frames half-way through production, and you feel the freshly applied first welds in your nostrils, it feels soooo good!! [Yes, some women prefer the smell of welding over the smell of nail polish :-)]

I hope that no storms will rage at sea so that all the cargo arrives safe and sound!

Great thanks to CORN Metaalbewerking in Hoogeveen for giving me a tour in their company and producing the skid frames!

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Measuring UniBoard2

April 23, 2017, 5:00 pm

≫ Next: Oort Lecture to be given by Imke de Pater

≪ Previous: I-LOFAR skid frames halfway through production

One of the major challenges in developing processing platforms for the SKA is cooling the boards. In the past boards are cooled with air, like the processing boards in LOFAR for example. Nowadays experiments have been done with liquid cooling for UniBoard and UniBoard2. However, next generation boards need even more power to cool. In collaboration the DESP and mechanical group are exploring new cooling solutions for the Gemini processing boards in the SKA Low telescope.

Flatness and the angle of components are key parameters for mounting water blocks onto a board. To measure this Sjouke Kuindersma has done measurements on UniBoard2 to analyze the flatness and the angle between the board and the FPGA (Field Programmable Gate Array). From this measurement was concluded that the FPGAs are flat (

As seen in the image the cross-domain knowledge together with the knowledge of CSIRO is used to develop the best processing board for the SKA-Low correlator and beamformer.

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Oort Lecture to be given by Imke de Pater

April 24, 2017, 5:00 pm

≫ Next: Wurzburg radar dishes

≪ Previous: Measuring UniBoard2

This year's Oort Lecture is to be given in Leiden on May 11th by our very own Imke de Pater. The lecture will be given in English, and is free of charge, but those interested are assumed to be sophisticated enough to decipher the information in the above announcement. Highly recommended.

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Wurzburg radar dishes

April 25, 2017, 5:00 pm

≫ Next: The King's 50th birthday

≪ Previous: Oort Lecture to be given by Imke de Pater

A new museum is being founded in the island of Terschelling, in the North of The Netherlands. Hundreds of bunkers have been built there during WW II by the Nazi occupiers, as part of the Atlantic wall defence line. This bunker complex was called Tigerstellung and includes several early radar installations.

The Freya Radar, operational since 1941. This 360 degrees rotating radar installation was 15 meters high, and could detect planes at a range of about 120km, but was unable to measure the altitude of the plane.

The Wurzburg Riese radar. This is one of two tracking radars of this type. The radar could rotate 360 degrees and could determine distance and altitude to planes, with a range of 60km.

The latter also played a role in Dutch radio astronomy. Two Wurzburg dishes were used in Dwingeloo during the 70's, as an interferometer for high resolution solar observations. The development of radio astronomy, which probes the furthest reaches of the cosmos, has been greatly accelerated by the availability of radar ingenieurs and technology after the war.

http://bunkersterschelling.nl/bunkerstellingen/radarstelling-tiger/

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The King's 50th birthday

April 26, 2017, 5:00 pm

≫ Next: Today's Colloquium: The first Be/BH binary system in context: discovery, evolution and accretion/ejection coupling

≪ Previous: Wurzburg radar dishes

On April 27th 2017, our gracious King Willem Alexander turns 50. Since the four sister institutes in Dwingeloo (ASTRON, JIVE, NOVA and DOME) are no strangers to royal patronage, we celebrate King's Day by more than just not working. The image shows a lovely orange crown, which was produced in-house by means of 3D printing. It is tastefully placed on top of a bowl with 50 little crowns that were produced with the same advanced technique.

The Monarch's birthday has been celebrated at the end of April(*) since 1949, the year in which SRZM, the forerunner of ASTRON, was founded. It is deemed to mark the end of the miserably cold part of the Dutch spring, and thus the harbinger of better times.

(*) Since it is not always easy to ensure that the next monarch is born at the end of April, it has been suggested that we adopt the date of birth of the Father of the Dutch nation, William of Orange, on April 24th 1533.

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Today's Colloquium: The first Be/BH binary system in context: discovery, evolution and accretion/ejection coupling

May 3, 2017, 5:00 pm

≫ Next: LOFAR container sailing to Ireland

≪ Previous: The King's 50th birthday

In this talk I will explain the serendipitous discovery of the first known Be/black hole (BH) binary system, namely MWC 656, found after a possible gamma-ray flare detected by the AGILE satellite. I will discuss the importance of this discovery in the context of binary system evolution. In particular, I will comment on the Be/NS versus Be/BH ratio and I will show the possible evolution of MWC 656-like systems towards compact NS/BH systems that can merge and produce detectable gravitational waves in nearby galaxies.

In addition, X-ray/radio observations have revealed counterparts in both energy ranges, providing evidence of a quiescent black hole in a high mass X-ray binary for the first time, which follows the accretion/ejection coupling already known from low mass X-ray binaries. These results show that the accretion/ejection coupling in stellar-mass BHs is independent of the nature of the donor star.

Finally, recent and ongoing observations show a long-term variability whose physical origin has to be understood.

I will review all these discoveries related to the first Be/BH system MWC 656 and will provide an outlook of the current observational efforts aimed at better understanding Be/BH systems.

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LOFAR container sailing to Ireland

May 2, 2017, 5:00 pm

≫ Next: NGC 5395 and NGC 5394 - the Heron Galaxy

≪ Previous: Today's Colloquium: The first Be/BH binary system in context: discovery, evolution and accretion/ejection coupling

The “heart” of every international LOFAR station is perfectly guarded in a 20 foot container, preventing Radio Frequency Interference (RFI) coming out, or in.

Mounted in several 19-inch racks in this container, there are all receiver units for the 4x96 antenna signals and the required back-end processing units like Remote Station Processing boards and Transient Buffer Boards and finally a pile of Networking gear to relay all data to its ultimate users. Quite a decent assembly of delicate hardware.

A dedicated crew came along all from Ireland to collect this container from the ASTRON premises and ship it to its final destination in Birr, Co Offaly, Ireland where coming months a newly build LOFAR will arise for the I-LOFAR consortium (consisting of following universities and institutes: TCD, Armagh, UCD, DCU, UCC, NUIG, DIAS and AIT).

Crewmembers for this exceptional transport were Noel Howley, owner of an Irish Transport company providing an impressive truck and accompanied by Dr Ryan O. Milligan, a.k.a. “the truck driver turned NASA astrophysicist”. Dr Milligan not only will drive the truck back to Ireland but also while heading up to Birr will emphasize on the importance providing young people with innovating and challenging opportunities to build their skills by using highly innovative research facilities like e.g. a (LOFAR) radio telescope. He‘s in a race against time, Ryan has 2 days to complete 3 round trips to the docks at Zeebrugge harbour (BE). A crew from BBC UK took a lot of footage. The TV show is for BBC and will be seen in the UK and Ireland.

Before shipping the ILT container, it received it‘s CE mark. CE marking is a mandatory conformity marking for certain products sold within the European Economic Area. We are confident the ILT container meets these requirements easily, recognizing the sensitivity to RFI from its environment. It also might help smoothly passing customs, just in case.

Thanks to dedicated ASTRON crew members not only this ILT container was prepared shipment to Ireland, another two fully loaded trailers with LOFAR components did sail to Ireland. More than one reason to celebrate this with some cake.

This convoy safely has arrived in Ireland on Friday 28th. The ILT container now has landed on its final position at the site in Birr!

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NGC 5395 and NGC 5394 - the Heron Galaxy

May 1, 2017, 5:00 pm

≫ Next: Testing Gemini POC

≪ Previous: LOFAR container sailing to Ireland

NGC 5395 and 5394 are two interacting galaxies in the constellation of Canes Venatici, discovered in 1787 by William Herschel. The bigger galaxy is NGC 5395, and the smaller one is called NGC 5394. The latter is believed to have cart-wheeled through NGC 5395. It's also known as Arp 84, and the two galaxies bear a striking resemblance to a blue heron. At a distance of 165 million light years, the galaxies appear quite small - subtending an angle of about 2.5 x 1.5 arc minutes.

This image is a LRGB combination of 15 hours worth of data, collected with a 0.4m telescope in Beilen. It will probably be one of the last images acquired there, for the telescope will soon be relocated to a much darker site in Germany.

The full image can be seen at: http://www.astrobin.com/full/292005/C/ Many faint galaxies can be seen in the background.

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Testing Gemini POC

April 30, 2017, 5:00 pm

≫ Next: Making custom designs is FUN :)

≪ Previous: NGC 5395 and NGC 5394 - the Heron Galaxy

The image shows the testing of the Gemini POC (Proof Of Concept). The first achievement was a flashing LED. Although a simple flashing LED looks simple, a lot of engineering is required to achieving this. Therefore, a flashing LED gives much joy to the engineers. The flashing LED shows that all power supplies are working and the FPGA (Field Programmable Gate Array) can be configured. The power delivery network for a modern FPGA is challenging because of the high core supply current (100A) and the requirement that all 11 power supplies are switched on in a defined sequence.

The optical interfaces on the board have been tested as well. These interfaces have speeds of 25Gbps per transceiver of which 52 are implemented on Gemini resulting in a total throughput of 1.3 Tbps.

To gain more knowledge about the power consumption and the heat distribution of the board, a heater design has been made which uses as much resources from the FPGA as possible to maximize its power usage. In the image the thermal image is shown. The test proved that the power supplies can handle the required power (almost 100W) to the FPGA.

Now that most concepts are verified we can send out the design files for the next Gemini version and start working on the firmware designs for the SKA CSP-LOW Correlator and Beamformer.

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Making custom designs is FUN :)

May 4, 2017, 5:00 pm

≫ Next: Making custom designs is FUN :)

≪ Previous: Testing Gemini POC

From time to time mechanical engineers at ASTRON are faced with unusual requests. Apart from designing functional parts for radio telescopes, we also have fun addressing and answering questions like: "Paula, can you come up with something and design a custom made creative farewell gift?", "Do you have anything specific in mind?", "Nope. It should be nice".

What a question! "Creativity" is my second name!

Such speed/rush assignments are fun, because there are no limits - beside the time, and I can let my fantasy go wild. Try to combine the two - zero limits but design something cool looking and have it ready within 5 days.

End of March we bid farewell to our colleague RF engineer Martijn Brethouwer. I worked with Martijn within the MFAA team and I got familiar with his PCB design for the MFAA beam-former board. Hence, I decided to make something mechanical on basis of his beam-former board design. Obviously, the other main aspect that should be incorporated was ASTRON logo! What should the gift be made of? 3D printing offers the most design freedom hence the choice was self-evident.

The only bottleneck was the time, because although 3D printing is most of the time associated with "rapid prototyping", the meaning of word "rapid" is also relative. It is not that you send a file and one hour later you have it delivered at your desk. 3D printing and post processing products externally also takes some time. That was the reason why Martijn received only some photos of the finished CAD drawing of the gift.

The real deal has finally arrived and was printed at Shapeways. The pictures of the tactile gift are shown above. It is a 3D printed business card holder with an incorporated mechanical rendition of 1/4 of the MFAA beam-former board on top.

The holder is made of 2 layers. The inner pocket construction is based on a rectangular mesh with an incorporated spring for holding the business cards in place. If you look closely, you can also see the ASTRON logo at the background of the beam former board. The outside shell as you can see is mainly to remind Martijn of ASTRON, and one of the many assignments he completed. Moreover, the content of the holder should remind him of the people he worked with at ASTRON!

Enjoy your gift Martijn, it will be shipped to you soon!

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Making custom designs is FUN :)

May 7, 2017, 5:00 pm

≫ Next: Towards the origin of the radio emission in AR Sco, the first radio-pulsing white dwarf binary

≪ Previous: Making custom designs is FUN :)

What a question! "Creativity" is my second name!

Enjoy your gift Martijn, it will be shipped to you soon!

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Towards the origin of the radio emission in AR Sco, the first radio-pulsing white dwarf binary

May 8, 2017, 5:00 pm

≫ Next: More Apertif

≪ Previous: Making custom designs is FUN :)

The binary system AR Sco contains an M star and the only known radio-pulsing white dwarf. The system shows emission from radio to X-rays, likely dominated by synchrotron radiation. The mechanism of how most of the emission is produced remains unclear and two competing scenarios have been proposed: collimated outflows and direct interaction between the magnetospheres of the white dwarf and the M star.

We conducted a radio observation with the Australian Long Baseline Array (LBA) on 20 Oct 2016 at 8.5 GHz to study the compactness of the radio emission and discern between the two proposed scenarios. Simultaneous data with the Australian Telescope Compact Array (ATCA) were also recorded for a direct comparison of the obtained flux densities.

We have observed that AR Sco shows radio emission compact on milliarcsecond angular scales (less than four solar radii). As it can be seen in the picture, the emission is orbitally modulated, with an average flux density of around 6.5 mJy. A comparison with the simultaneous ATCA data shows that no flux is resolved out on mas scales, implying that the radio emission is produced in this compact region. Additionally, the obtained radio light-curves on hour timescales are consistent with the optical light-curve. This points to the fact that the radio emission in AR Sco is likely produced in the magnetosphere of the M star or the white dwarf, and we do not see evidence for a radio outflow or collimated jets significantly contributing to the radio emission.

This work has been accepted for publication in A&A: Marcote, Marsh, Stanway, Paragi, and Blanchard (2017, arXiv:1705.00600).

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More Apertif

May 9, 2017, 5:00 pm

≫ Next: Today's Colloquium: The HI4PI Survey

≪ Previous: Towards the origin of the radio emission in AR Sco, the first radio-pulsing white dwarf binary

A few months ago, it was even in the national press that the first, real image had been made with Apertif (see the AJPOD of 31-Jan-2017). Work on Apertif has been progressing steadily since then and more images have been made. The image above shows the active galaxy NGC 315 with its very extended radio jets. The extent on the sky of NGC 315 is about 1 degree and the complete object does not fit in a single beam of the telescope. So in the old days, several observations were needed to make a full image. Using the new `wide-angle' capability of Apertif, it can now be imaged in a single observation.

NGC 315 is a famous object. With its extent of over one Mpc, it is one of the largest single objects known in the Universe. It also has an old connection with ASTRON. It was first detected as a radio source in 1967 with the Dwingeloo dish and was named DW0055+30 (Davis 1967). Only later it was identified with the early-type galaxy NGC 315. The WSRT studies of this object done in the late 70's, involving Tony Willis and Richard Strom, belong to the canon of classic WSRT observations. Also around 2005 the object was observed with WSRT, this time to study the cold gas in and around the galaxy (Morganti+ 2009)

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Today's Colloquium: The HI4PI Survey

May 10, 2017, 5:00 pm

≫ Next: Announcing WimSym77: 6/7 July 2017

≪ Previous: More Apertif

The image shows the column density of neutral atomic hydrogen in our galaxy, the Milky Way. It is one result of a new 21-cm spectroscopic survey of the full sky, the HI 4-PI Survey (HI4PI). The HI4PI data set was merged from two recent surveys, the Effelsberg-Bonn HI Survey, made with the 100-m radio telescope at Effelsberg/Germany, and the Galactic All-Sky Survey (GASS), observed with the

Parkes 64-m dish in Australia.

HI4PI is the most sensitive all-sky HI survey ever performed, offering high angular resolution and very accurate flux density calibration. It is furthermore corrected for stray radiation effects.

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