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Winter 2018

LOFAR upgrade receives NWO Groot grant Gearing up for Apertif operations Next milestone for SKA-Low test station ASTRON News / Winter 2018

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Image cover: The Westerbork Synthesis Radio Telescope with Apertif upgrade.

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ASTRON News / Winter 2018


Contents Director's corner 5 LOFAR upgrade receives NWO Groot grant

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Focus on Complex Project Management in ASTRON

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LOFAR rapidly responds to a gamma-ray burst

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LOFAR operations during Cycle 10 and future challenges

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SAGECal: Full acceleration ahead

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Gearing up for Apertif operations

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LOFAR upgrade receives NWO Groot grant

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Gearing up for Apertif operations

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Dwingeloo telescope downloads image of Lunar far side and Earth

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LOFAR strides towards truly multi-tasking radio telescope

Outreach & Media 14 LOFAR for Space Weather: Evolving the System Design

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The First ASTRON/JIVE Traineeship Programme in Science Operations with Massive Arrays

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First step towards a Science Data Centre

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Looking for fast radio bursts at optical and very high energies

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Next milestone for SKA-Low test station

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Slow, slower, slowest... 23 WSRT’s major upgrade enlargers field of view 37 times

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The origin of the gamma-ray binary 1FGL J1018.6-5856

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SWENED collaboration 27 Achievements of the CITT2

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The duty cycle of the radio galaxy B2 0258+35

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DRT downloads image of Lunar far side and Earth

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LOFAR strides towards truly multi-tasking radio telescope

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HI absorption workshop 2018

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Symposium The new era of multi-messenger astrophysics

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ASTRON News / Winter 2018

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Colophon

Editorial

ASTRON Netherlands Institute for Radio

Over the last couple of months, we had

enlarged 37 times. Apertif is now about

Astronomy.

some great results and activities. First of

to transition from development into

all, great news for LOFAR 2.0. An NWO

operations. Early Apertif surveys will

Our mission is to make discoveries

Groot Grant has been awarded to

start on 1 January 2019.

in radio astronomy happen, via the

ASTRON and Leiden University by the

development of novel and innovative

Netherlands Organisation for Scientific

Like last year, we organised our open

technologies, the operation of world-

Research (NWO) in order to build and

day. More than 500 people visited the

class radio astronomy facilities, and the

deploy DUPLLO: the Digital Upgrade for

ASTRON/JIVE/NOVA open day during

pursuit of fundamental astronomical

Premier LOFAR Low-band Observing.

the Science Weekend (Weekend van de Wetenschap). The day was filled with

research. In other LOFAR news, LOFAR will

activities around the theme 'Building

Address

be able to carry out simultaneous

the world's largest (radio) telescopes'.

Oude Hoogeveensedijk 4

observations for several science cases.

We think the open day was a big

7991 PD Dwingeloo

This is possible because of the new

success.

The Netherlands

brain for LOFAR, COBALT 2.0. This is a

Tel. +31 521 59 51 00

great update for LOFAR and is future

The telescope in our backyard, the

proof and is amongst the most energy

Dwingeloo Radio Telescope, helped

ASTRON News

efficient (greenest) HPC correlators that

downloading an image of the Lunar far

Editorial team | Gina Maffey , John

is possible with the current technology.

side and Earth. The image was taken by a Chinese lunar orbiting satellite.

McKean, Roy van der Werp, Stefan Wijnholds.

Last September Apertif was officially

The satellite that took this picture

Email: pr@astron.nl

opened by deputy Cees Bijl of the

was launched in May together with

Drenthe province. The opening was

the larger satellite Chang’e 4 that

Published

a great success and we were lucky

also carries the NCLE payload built by

Twice a year

enough to have fantastic weather.

ASTRON, the Radboud Radio Lab and

ISSN nr. 1871-6644

Besides the opening of Apertif, we

ISIS.

also celebrated the 50-year anniversary of the Westerbork Synthesis Radio

As always, enjoy reading the winter

Telescope with the release of the book:

edition of the ASTRON News and we

50 years Westerbork Radio Observatory.

wish you a Merry Christmas and a

A continuing journey to Discoveries and

Happy New Year.

Innovations. And because of Apertif, the field of view of the Westerbork Radio Telescope

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ASTRON News / Winter 2018


Director’s corner Approaching the end of a year gives us all the opportunity to reflect on our significant achievements. It is clear that 2018 has been as busy as ever with more demanding systems projects requiring focus and consolidation to be successfully delivered.

and it is extremely gratifying to have them build and support the vision for LOFAR 2.0. Recognising that LOFAR 2.0 is a complex and challenging series

With its large and very visible location in the former Reading

program we are committed to improving ASTRON’s organisational

Room, the Apertif team has made fantastic progress to deliver

management and engineering disciplines with formal and

systems to commence observing in January 2019. A number

informal training sessions, personal development and mentoring.

of ‘firsts’ have been achieved by this team including full beam

This is an ongoing effort, committed to ultimately delivering

calibration. Apertif is the largest and most comprehensive system

systems, upgrades and innovations that underpin our mission to

upgrade ever attempted for the Westerbork Synthesis Radio

make discoveries in Radio Astronomy happen.

Telescope (WSRT): it is both remarkable and perhaps fitting that in the last period we also celebrated the 50th anniversary of the

Whilst our efforts to secure membership for the Netherlands

WSRT with an event along with the launch of the Apertif systems.

in the SKA continue with a detailed funding plan for national

All of these activities are reported in more depth in articles this

membership, the actual design work by ASTRON engineers, in

issue.

partnership with our international colleagues has continued apace. Most of the SKA system elements will have concluded their

It is also gratifying to have the WSRT’s 50 year history captured

Critical Design Reviews by the time this News is published: from

in a new publication, led by Editors Arnold van Ardenne, Richard

here on we are engaged in the pre-construction ‘bridging’ to be

Strom and Steve Torchinsky and dedicated to our highly respected

ready for the build.

colleague, Prof Ger de Bruyn. The efforts of the editors and all of the author/contributors are much appreciated in compiling this

Clearly 2019 is going to be another busy and highly productive

comprehensive summary of the WSRT’s past, present and future.

year on all fronts. Mid November saw the opening of the new BytesNet facility in Groningen: we anticipate locating our Apertif

As many readers will know, there are major developments for

long term archive in this facility, working with BytesNet as a

LOFAR and ILT underway. The basis of these is the in-house

commercial partner to establish a first tangible part of our data

“LOFAR efficiency improvement” program that will consolidate

science infrastructure. Our new Institute Advisory Board (IAR) will

experience with LOFAR and also provide a powerful platform

hold its first IAR meeting in December 2018. The timing is good.

of operational capability for the next 10-15 years. This suite

The national assessment of all Dutch (KNAW and NWO) Institutes

of upgrades will augment the underlying systems (software,

will soon be concluding, with the publication of recommendations

data and observations management databases, etc) to ensure

due in February 2019.

LOFAR can ingest new pipelines and algorithms, and also to our operational systems to reduce the required hands-on

As ever, please enjoy this latest “News” from ASTRON. I wish

management of the LOFAR observing process itself. The other

everyone a very Happy Christmas and a prosperous New Year.

major LOFAR development program is the suite of station and system upgrades captured as phase 1 of the “LOFAR 2.0” program. This program coheres a series of improvements to LOFAR’s capabilities, including the newly-awarded NWO-G grant “DUPLLO”. LOFAR 2.0 is now run as a single program comprising a team of engineers, astronomers and operations support experts to develop a full systems-delivery plan from the outset. Our International LOFAR Telescope partners are key to this success too,

Carole


LOFAR upgrade receives NWO Groot grant The International LOFAR Telescope (ILT) is the world’s largest and most sensitive low-frequency radio telescope. The members of the ILT tasked ASTRON to lead a staged upgrade program (LOFAR 2.0), such that the Low Frequency Array (LOFAR) will continue to develop and remain the world’s most powerful very-low-frequency, and long-baseline, radio interferometer until at least 2030.

the 110 – 240 MHz band. The LOFAR high-

maximising the image fidelity. This will be

band antennas (HBA: 110-240 MHz) enable

achieved by:

sky images to be made with a sensitivity and resolution that far exceed the previous state-

• Doubling the number of active LBA

of-the-art.

antennas, • Installing a centralised high-precision clock

The next challenge is to apply these

distribution system, and

techniques at frequencies below 100 MHz

• Using joint LBA+HBA antenna data to

(where the ionospheric distortions are much

accurately model and remove ionospheric

stronger) to fully exploit the scientific promise

disturbances, which are strongest at low

of the LOFAR low-band antennas (LBA:

frequencies. This requires the development

10-90 MHz). At the same time, an improved

of substantially more sophisticated

operational efficiency and maintainability

calibration techniques, and a major hardware

is desired, and LOFAR needs to be made

enhancement to the LOFAR station electronics.

robust against changes in the interference environment (such as windmills and

The official LOFAR 2.0 development

communication signals).

programme kicked off last March. The main focus thus far has been to establish a solid

First stage

systems engineering basis for the upgrade:

DUPLLO is the first major upgrade to LOFAR

use cases, science requirements, operational

Wim van Cappellen, Jason Hessels

that will enable pioneering astrophysical

concepts and system requirements are being

(cappellen@astron.nl)

research using absolute lowest radio

defined. In parallel, various technology

frequencies visible from Earth. Through

options have been considered.

NWO Groot grant for DUPLLO

improved collecting area and calibration, we

A €3,450.000 NWO Groot Grant has been

will increase LOFAR’s LBA imaging sensitivity

awarded to ASTRON and Leiden University by

by a factor of roughly 5, while simultaneously

the Netherlands Organisation for Scientific

pushing to lower frequencies (<50 MHz) and

Research (NWO) in order to build and deploy DUPLLO: the Digital Upgrade for Premier LOFAR Low-band Observing. DUPLLO is a key element of the LOFAR 2.0 program and will greatly enhance the sensitivity and discovery potential of LOFAR at the lowest radio frequencies visible from earth. In doing so, it will enable deep observations through an unexplored window on the Universe. Upgrades for LOFAR After its inauguration in 2010, LOFAR has become a great success and is now producing, on average, a scientific paper every week. Key to this success is the ability to routinely compensate for the distortion of the astronomical signals by the ionosphere in

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ASTRON News / Winter 2018

Figure 1: NWO Groot grant ceremony, Stan Gielen handing out the certificates.


Figure 2: An overview of how DUPLLO provides a major enhancement to the LOFAR telescope.

ASTRON News / Winter 2018

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Focus on Complex Project Management in ASTRON

What are the most important skills for project leaders? Project reporting, and dealing with “hard” decisions. Further sessions tackled project management tools, making project reviews more effective, managing complexity, risk, contingency, building project resilience, and application of Phil’s CHiPS tool, a carefully crafted 60

A new collaboration commenced in April with a visit by Dr Phil Crosby, Business Strategist and Major Project Specialist with Australia’s CSIRO Astronomy and Space Science.

point checklist shown to lift complex project performance. The week concluded with diagnostic sessions for LOFAR 2.0 and APERTIF, however impetus has not been lost as follow-up action is already planned. This centres on a

Phil kindly agreed to spend a week at

review of development of ASTRON’s project

ASTRON delivering a series of lectures, project

management skills, implementation of an

team coaching, and one-on-one discussions

effective lessons learnt system, work to

focussing on lifting project success through

resolve program/project tracking issues, as

better understanding of the nature of

well as promoting a project management

complex projects, and early strategies to avoid

“Community of Practice” culture at ASTRON.

failure. The week of intense activities was carefully planned with Dr Gert Kruithof and Dr Hans Jense to maximise interactivity and learning between groups, and specific project teams. After scoping the exercise with members of the Management Team, a programme was developed to address the challenges of complex projects leading from the theoretical to the practical application of techniques. Phil opened proceedings with an all-hands talk on his research; “Achieving Success in hightechnology project management”, followed by a lively session dealing with key questions; e.g. Do complex, high-tech projects need different managing? What organisational relationships work best?

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ASTRON News / Winter 2018


LOFAR rapidly responds to a gamma-ray burst

during the time that the Swift Observatory

LOFAR will continue to observe new transient

was monitoring the X-ray counterpart. Our

sources detected by other facilities to deeply

observations coincided with a â&#x20AC;&#x2DC;plateau phaseâ&#x20AC;&#x2122;,

search for coherent radio emission.

during which there may be coherent radio emission. Although there was no detection, our observations give the deepest limits on this type of emission to date.

On Friday 6 July 2018 at 10:25 am (CEST), just 4 minutes after receiving an alert, LOFAR started observing the location of a gammaray burst. This was the very first time normal operations were fully automatically interrupted to respond to a transient alert. Antonia Rowlinson (rowlinson@astron.nl) As part of the ASTERICS programme, we have successfully implemented a new rapid response mode for LOFAR. This allows us to automatically start observations within 5 minutes of an alert; enabling a search for coherent radio emission from transients such as gamma-ray bursts. The Neil Gehrels Swift Observatory scans the sky in real time to search for, localise and study gamma-ray bursts. These brief flashes of gamma-rays are caused by the violent deaths of massive stars or the merger of neutron stars. Following the gamma-rays, there is a multi-wavelength afterglow. Theories predict that, very early on, there is coherent radio emission from these events. On Friday 6 July 2018, LOFAR automatically responded to a gamma-ray burst that was detected by the Swift Observatory. A 2-hour observation started 4 minutes after the alert,

Figure 1: The top panel shows the gamma-ray (black) and X-ray (blue) flux as a function of time for this event. The red region shows the time of the LOFAR observation. The panels below show the upper limits on the radio emission using different snapshot timescales. From Rowlinson et al. (in prep).

ASTRON News / Winter 2018

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LOFAR operations during Cycle 10 and future challenges November 14th 2018 marked the end of the eleventh LOFAR operational Cycle, Cycle 10. During this semester, successful science operations progressed side-by-side with maintenance activities and software development. The Radio Observatory is working hard to prepare for new system upgrades which will improve the efficiency of the observing system. Roberto Pizzo (pizzo@astron.nl)

taken to significantly improve the handling

the people who will operate next generation

of the large flow of data through the system

facilities like SKA. To achieve this, we have

and advance the production processing

successfully completed the first traineeship

pipelines to deliver more advanced data

programme in ‘Science Operations with

products to the community.

Massive Arrays’ and are already preparing for the next programme in 2019.

Dysco, the visibility compression tool, is active in production since early September and

With important achievements accomplished

allows the compression of imaging data by

already, the Radio Observatory is working

a factor of 3.6 without significant sensitivity

hard on very crucial challenges associated

loss. We have continued enhancing the data

with the “LOFAR observing efficiency

quality monitoring procedures through

project”. This will run for the next two

the development of a new generation

years and, when completed, will deliver a

of inspection plots based on artificial

more robust and automatic system to the

intelligence algorithms, which should become

community. In particular, it will enable the

available in production by the end of the

Radio Observatory to offer most of the

year. Moreover, we have taken steps towards

telescope time as regular observing time,

delivering more advanced data products

realising uniform observing efficiencies of the

to our community of users by starting the

order of 75%.

deployment in production of new imaging pipelines, which should be offered to the

The important work described above

community in the Cycle 12 proposal call.

translates into an ever-increasing scientific productivity of LOFAR. To date, more than

Cycle 10 covered the period 15 May – 14

Over the past years of operations, the Radio

200 LOFAR papers have been published in

November 2018. The Cycle 10 proposal

Observatory has clearly acquired significant

the professional literature and publications

call was a particularly important one, as

experience in operating massive arrays like

are produced at a rate of one per week (see

it allowed proposers to submit long-term

LOFAR and it is imperative to share it with

figure).

proposals and have access to part of the telescope time also for the upcoming Cycles, till the end of Cycle 13. In total, 8700 observing and 7800 processing hours were allocated to 13 long-term proposals. Additionally, 670 observing and 920 processing hours were allocated to 21 single-Cycle 10 projects. By the end of the semester, 95% of the observing programme was completed and the rest is being observed with second priority in Cycle 11, as per Radio Observatory policy. During the past semester, maintenance activities and software development progressed side by side with successful science operations. Specifically, important steps were

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ASTRON News / Winter 2018


SAGECal: Full acceleration ahead

Computation of the model involves evaluation of many millions of transcendental functions that are expensive CPU operations. Using GPU acceleration, we get an order of magnitude speedup as shown in Figure 1. We have also shown the scalability of the

To look deeper in the Universe, radio telescopes are becoming more and more sensitive, at the cost of delivering larger and larger volumes of data. In order to produce images that reveal the faintest sources, we need software to calibrate these large amounts of data in an accurate and efficient manner.

acceleration, expanding from LOFAR to SKA. SAGECal is in good shape to handle increased data volumes generated by any future radio telescope.

Hanno Spreeuw (h.spreeuw@esciencecenter. nl) Sarod Yatawatta (yatawatta@astron.nl) We started developing SAGECal over a decade ago, mainly to serve the LOFAR Epoch of Reionisation key science project. In order to detect weak reionisation signatures from the early Universe, Terabytes of LOFAR data need to be accurately calibrated and calibration has to be done as fast as possible. We have accelerated every operation in SAGECal using Graphics Processing Units (GPU). Initially, the various non-linear optimisation routines used in calibration were accelerated. A major bottleneck thus far has been the computation of the model that is needed to run the optimisation routines. The model consists of thousands of celestial sources, some having exotic components such as shapelets. Additionally, the phased array beam shape needs to be computed along the

Figure 1: SAGEcal sky and beam model computation time for five simulated data sets with stations increasing from 64 to 512, and for five different sky models with varying number of sources. We have used a computer equipped with CPUs (2 Xeon ES-2660-v3, 40 logical cores) and a Titan-X (Pascal) GPU on ASTRONâ&#x20AC;&#x2122;s DAS5 cluster.

directions of every source.

ASTRON News / Winter 2018

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Gearing up for Apertif operations

planning observations and related tasks. We

beams, amounting to nearly three thousand

also used ARTAMIS (All-Round Telescope Array

beams on sky. The main effort has been to

Monitoring and Information System) for real-

automatically process the resulting data and

time monitoring, and tested automation for

classify the many candidate transients detected

the Apertif imaging inspection plots (see: http://

by the ARTS pipeline in each of these beams.

apertifsurveys.wordpress.com). To drastically reduce the number of beams

Apertif is about to transition from development into operations. We have recently stress tested the system and verified if all elements needed for operations are in place.

The time-domain mode of Apertif is controlled

required to fill the entire Apertif field of view,

by a dedicated backend, the Apertif Radio

ARTS was run in an incoherent mode during

Transient System (ARTS). ARTS is built of forty

the shakedown period. This comes at the

servers equipped with four high-performance

cost of reduced sensitivity. The ARTS pipeline

GPU cards each. In itself, it is the most powerful

was running alongside the observations

computational system available in the

in real-time and e-mailing a summary of

Betsey Adams, Ă gnes Mika, Vanessa Moss,

Netherlands. Getting all these GPU-equipped

interesting candidates to the team. This led

Leon Oostrum and Arno Schoenmakers on

servers to behave properly has proven to be a

to the detection of single pulses from pulsar

behalf of the Apertif and ARTS teams

complicated yet rewarding process.

B1933+16, as shown in Figure 2.

(mika@astron.nl) For each of the forty compound beams Early Apertif surveys will start on 1 January

produced by the Apertif beamformers, ARTS

2019. In order to prepare for this new phase,

can create multiple coherently added tied-array

we carried out an Apertif "shakedownâ&#x20AC;? from 12 to 22 October. The aim was to test the operational readiness of the imaging, timedomain and calibration modes as well as the archiving capabilities. Thanks to the efforts of many people, the shakedown period was an overall success, while also identifying lots of areas to improve before the real start in January. The shakedown period provided a great opportunity to highlight some of the operational tools that have been developed at ASTRON (Figure 1). Two key aspects of the Apertif data flow are ALTA (Apertif Long-Term Archive) and ATDB (Apertif Task Database). ALTA is a 1.5 PB data repository which stores data and metadata for both the imaging and time-domain modes, while ATDB has recently been adopted for imaging, handling everything from observation specification and scheduling to ingest to ALTA. ATDB greatly increases the efficiency of preparing and

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ASTRON News / Winter 2018

Figure 1: The Apertif shakedown made use of various operational tools, such as ATDB, ALTA, ARTAMIS and a fully-automated inspection plot procedure. Image credit: N. Vermaas, H. Mulder, V. Moss.


The Apertif imaging surveys will use the large field of view provided by the forty compound beams of Apertif to make radio continuum maps and neutral hydrogen data cubes over large regions of the sky. The imaging survey will observe in two tiers: a single shallow pointing over a larger region (called the “shallow northern sky survey”) and multiple pointings

Figure 2: Single pulse of PSR B1933+16 after dedispersion; (top) Timeseries of the pulse (bottom); Pulse intensity over the 300 MHz wide frequency band. Credits: L. Oostrum, L. Connor.

to build up sensitivity over a smaller area (called the “medium deep survey”). Gearing up for operations and survey observing early next year, we used the shakedown period to observe several pointings from the planned survey footprint for both survey tiers. These observations served multiple purposes: evaluating the observing and calibration strategy, stress-testing the current state of the reduction pipelines, and assessing the data quality. We learned a lot about our readiness for the surveys and had fun looking at lots of data, including producing the first full-field image with compound beams (Figure 3, produced entirely in the Apercal pipeline, developed for the purpose of automating Apertif imaging). The action points that came out of this shakedown period have been identified and added to the work list of the ARTS and Apertif development team. We plan to have tackled many of these by the time that we will have the next shakedown period, from 7 to 12 of December. This period will be the final rehearsal before Apertif goes operational.

Figure 3: A full-field continuum image produced automatically by the Apercal pipeline. This image is comprised of 37 of the final 40 compound beams. The full moon is shown for scale, representing the field of view of a single WSRT beam. Image credit: H. Dénes.

ASTRON News / Winter 2018

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Outreach & Media

related fields, both non-technical and technical

is" or "just because" can save them up for the

and ranges from policy and law, business and

annual Klokhuis Vragendag at NEMO. Two of

Over the last few months we have published several interesting news stories that were well received in the media. We also organised visits and outreach events.

management and humanities to life sciences,

the questions were "Can you smell in space"

engineering, physical sciences and space

and "Where does Wifi come from". Well, we

applications. SSP participants are high potential

know the answer to those two very well here.

Roy van der Werp (pr@astron.nl)

Let's Gro To The Moon

about 40 scientists from various disciplines.

This year's "Let's Gro" festival, aimed at

Using models, laptops, and taking brains (still

Open day 2018

inspiring people to create an active, innovative,

bloody) from jars.

On Saturday 6 October 2018, more than 500

and sustainable future for the city of Groningen

people visited the ASTRON/JIVE/NOVA Open

and its 'ommelanden'. The festival was from 31

There was also the traditional Vraag Maar Raak

Day during the Science Weekend (Weekend

October to 3 November.

show. Here, a cognitive scientist, biologist,

scientists and engineers in the field of space in their early career from 35 different countries.

This year, over 500 kids submitted questions, and these were all answered by a team of

chemist, physicist and an astronomer had to

van de Wetenschap). One of the many activities included a Moon-

answer 10 questions in 20 minutes. Joeri van

The day was filled with activities around the

walk explaining the why and how of Lunar

Leeuwen tried to answer the most astronomy

theme 'Building the world's largest (radio)

phase and eclipses, Earth's tides, and space

related questions.

telescopes': from an interactive interferometry

travel. This excursion ended at the Waagplein

demo showing how our radio telescopes

next to the City Hall, under a 7m diameter

Kids wrote down questions when entering the

work, a data path illustrating the increasing

Moon created by the British artist Luke Jerram,

theater, these were drawn from a large vat,

amounts of data we have to deal with, coding

see picture. From ASTRON, Albert-Jan Boonstra

and then it was up to the audience to decide

workshops, R&D and Correlator tours, to

had the honour to present our ASTRON Lunar

whether the team had demonstrated and

building mini-SKA dishes and pulsars with kids.

NCLE receiver work, during two general public

explained well enough what they learned. If

excursions on Thursday evening.

they did not make it, they had to dance. If they did, they received high-fives. Given the many

The many activities all showcased the amazing work we do here at ASTRON, JIVE and NOVA.

After explaining celestial dynamics by word and

available props, some questions were doable

by body movement, the group arrived under

(such as: "Why are there tides", explained

Space studies visit

the south pole of the Moon, where they had

above by dancing out an Earth-Sun-Moon

In August, the renowned Space Studies

an awesome view despite the heavy rain. The

system). Others were harder -- the worst one

Programme (SSP) from the International

1969 Apollo 11 landing site was visible a bit

being "Why is there gravity". If Joeri only knew

Space University visited ASTRON/JIVE/NOVA

higher-up at the 'near-side' of the Moon. At

that ... Still they managed, and were paid with

in Dwingeloo. During the visit, participants

this scale, the Chang'e 4 communicaton satellite

a few hundred high-fives.

learned about the institutes, got tours

carrying our NCLE receiver, was hovering nearly

through the facilities, learned about telescope

two hundred metres South in the direction of

engineering, the James Webb Telescope, space

the Herenstraat. The group was able to spot

VLBI and Space Weather, and visited the Low

the Chang'e 4 Lunar Lander area in the Aitken

Frequency Array (LOFAR).

crater, where it hopefully will successfully land after an envisioned launch in November.

The SSP is a nine-week graduate top-level professional development program conducted

Klokhuis Vragendag (Question Day) @ NEMO

by the International Space University (ISU).

Kids with burning questions that want a

The curriculum covers the principal space

different answer than "that's just the way it

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ASTRON News / Winter 2018


ASTRON News / Winter 2018

15


LOFAR for Space Weather: Evolving the System Design The LOFAR4SW design, being undertaken under a Horizon2020 design study project, is developing rapidly following a recent Science and System Definition Workshop, and is now being prepared for the Preliminary Design Review.

The workshop focussed on finalising and

cases) scenarios and how the telescope would

defining the space-weather science and

need to change modes automatically to

monitoring desires, converting the science

capture the increased science opportunities

requirements that were fed into the

during enhanced space-weather activity.

workshop into the higher-level requirements

Initial thoughts on the Operational aspects

needed to further develop the hardware and

of the LOFAR4SW system were discussed,

software design.

alongside much valuable work on the HBA tile beamformer design and potential

These are key steps in the progress towards

implementation of it based on the â&#x20AC;&#x153;evolvingâ&#x20AC;?

the documentation for the Preliminary

requirements throughout the workshop

Design Review (PDR) scheduled for 2-4 February 2019.

The workshop was a very-intense affair, and has set us on a strong path for PDR

The core set of observing requirements for

preparations.

general space-weather monitoring were set along with space-weather science (interesting

Pieter Benthem (benthem@astron.nl), Mario Bisi (UKRI), Richard Fallows (ASTRON) The LOFAR4SW design study addresses all conceptual and technical aspects required to upgrade the LOFAR radio telescope, systemwide, to take on a parallel role as a highly innovative new facility that enables largescale monitoring projects generating unique data for the European (and worldwide) space weather research community, offering great potential for improved precision and advance warning of space weather events affecting crucial infrastructures on earth. The main goal of the Science and System Definition Workshop, hosted in Cardiff, 1720 September 2018 was to to translate the LOFAR space weather use cases into science and system requirements. The workshop was hosted/organised by UKRI (formerly STFC). There were a total of 21 participants from across all partners. A photograph of the majority of the participants can be found as figure 1.

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ASTRON News / Winter 2018

Figure 1: Group picture of the attenees of the LOFAR4SW Science and System Definition Workshop at Cardiff.


The First ASTRON/ JIVE Traineeship Programme in Science Operations with Massive Arrays

LOFAR and the EVN, thereby developing

We cannot speak highly enough of the

the requisite skills in order to operate next-

experience provided by the traineeship; and

generation astronomy facilities such as the

in particular, the opportunity given to us to

SKA. To achieve this goal, we were assigned

act as telescope scientists on duty and lead

mentors within the Science Support Teams

daily operational meetings and activities. This

at ASTRON and JIVE, who taught us how

helped boost our confidence in the overall

to master independently the complex array

science operations of the LOFAR instrument.

of tasks required for supporting LOFAR and

We found the work environment at ASTRON

EVN observing programmes. The traineeship

and JIVE very friendly and gave us the

took the form of lectures, workshops, talks,

opportunity to engage in daily interactions

colloquia, discussions, site visits, hands-on

with scientists, engineers and support staff

experiences and operational duty assignments.

working at the institute.

In 2018 ASTRON and JIVE initiated a new flagship training programme, named “Traineeship in Science Operations with Massive Arrays”. The aim was to share the expertise in operating massive arrays ahead of next-generation world-class astronomy facilities such as LOFAR and SKA. The first traineeship was held from 7 May – 27 July at ASTRON and JIVE, for two participants (Bernard Duah Asabere and Emmanuel Bempong-Manful), who both came from a SKA AVN (African VLBI Network) partner country, Ghana. Below is a report from Bernard and Emmanuel on their experiences during the programme.

A very important and useful segment of the

We have learned so much and further

traineeship was the introduction to the JIVE

consolidated our knowledge and background

SFX Correlator and the ASTRON infrastructure

in radio astronomy. More importantly,

which consisted of visits to the LOFAR core

we have acquired hands-on experience

station, the central processing site (COBALT

in the science operations of cutting-edge

and CEP clusters) in Groningen, the Long

astronomical facilities, and we feel privileged

Term Archive (LTA) site at SURFsara and the

to have been part of this journey. It was

Westerbork Synthesis Radio Telescope. We

indeed a once-in-a-lifetime experience that

were given tours of these facilities by experts

we recommend every young radio astronomer

to learn about their operation and overall

(either at Postdoc, PhD or graduate student

scientific capabilities.

level) to have at some point in their career.

Emmanuel Bempong-Manful (e.bempongmanful@bristol.ac.uk) and Bernard Duah Asabere (bd.asabere@gmail.com) The 12-week traineeship programme included 11 weeks of full exposure to the LOFAR system and operations, and one week of training in VLBI operations and science at JIVE. The programme aimed at giving the trainees the opportunity to acquire expertise in operating Figure 1: Group photo of trainees with SOS group of ASTRON at the institute in Dwingeloo.

ASTRON News / Winter 2018

17


First step towards a Science Data Centre

d’ROOT will be used by various knowledge and research institutes and innovative companies from the region. d'ROOT also has facilities for high performance computing. These supercomputers with large processing power are required for scientific research and the processing of big data.

On 14 November minister Van Engelshoven (Education, Culture and Science) officially opened the Data Competence Centre d’ROOT in Groningen. The new Data Competence Centre of Bytesnet in Groningen is an innovative data centre with great added value for the Northern region of the Netherlands. ASTRON will be one of the tenants of d’ROOT. We are excited that we were part of the opening of d’ROOT. Where we plan to host our 15 petabytes WSRT-Apertif data archive. It’s the first step towards a Science Data Centre, which will become the hub for massive datasets that all scientists can access. "It is great to have Bytesnet Groningen as an enthusiastic partner as ASTRON develops towards the future. These data facilities are increasingly required for our research. With our focus on studying the Universe we will develop many talented data analysts who will also find careers well beyond research”, said ASTRON Director General Prof Carole Jackson. “Data from science must be accessible to everyone and this data centre is an excellent step”, said science minister Ingrid van Engelshoven.

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ASTRON News / Winter 2018


Looking for fast radio bursts at optical and very high energies

gamma-ray emission was detected, neither of

However, this detection is consistent with a

a persistent nature nor burst-like associated

spurious background event. All these results

with the FRBs. These results constrain the VHE

constrain the current FRB models (see MAGIC

luminosity to be lower than 1045 and 1049 erg

Collaboration et al. 2018, MNRAS, 481, 2479).

s-1, respectively. We also constrained the optical emission in the U band to be below 8.6 mJy at 5Ď&#x192; confidence level for 1-ms bursts around the FRB arrival

FRB 121102 is the only Fast Radio Burst known to repeat and precisely localised. Multi-wavelength observations with Arecibo and the MAGIC telescopes have been conducted to search for possible bursts at optical wavelengths and very high-energy gamma-rays.

times. A bright (29 mJy) 12-ms optical burst was detected 4.3 s before the arrival of one FRB.

Benito Marcote (marcote@jive.eu) and Tarek Hassan (tarek.hassan@desy.de) The origin of Fast Radio Bursts (FRBs) remains unclear. The discovery of the only repeating FRB, FRB 121102, and its precise localisation (see ASTRON Summer 2017 Newsletter) allowed the astronomers to study one FRB in detail for the first time. Several scenarios predict the emission of bursts outside the radio wavelengths, such as at optical wavelengths or even gamma-rays. However, the only way to unveil if FRB 121102 exhibits bursts at other wavelengths is to conduct simultaneous sensitive observations with different facilities. We conducted observations of FRB 121102 with Arecibo and the MAGIC Telescopes during 2016 and 2017 to search for optical and very high-energy

Figure 1: Illustration of the MAGIC-II telescope observing at the arrival time of one of the radio bursts from FRB 121102 detected by the Arecibo Telescope.

(VHE; >200 GeV) gamma-rays. During these observations a total of five FRBs were detected by Arecibo. No significant VHE

ASTRON News / Winter 2018

19


Next milestone for SKA-Low test station

coarse channel level such that there is no bandwidth decorrelation over the

This report is a summary of work that has

channel).

formed part of the large documentation set submitted for LFAA CDR, specifically the LFAA

3.

Verifying the mappings between antennas (including location and

Demonstrator Test Report.

polarisation labels), through the analogue and digital systems, to voltage

Initial bootstrapping

Steady progress is being made to characterise and verify the performance of the SKA-Low prototype system Aperture Array Verification System 1 (AAVS1). AAVS1 is a full-scale prototype system consisting of 256 "SKALA2" (SKA Log-periodic Antenna 2) log periodic dipole antennas arranged in a pseudo-random configuration with diameter 35 metres.

While the primary outputs of SKA-Low

Pieter Benthem (benthem@astron.nl), Randall

Using debugging and/or calibration modes

data format. This dataset was collected in

Wayth (ICRAR), Giuseppe Pupillo (INAF)

of the station firmware, standard radio

April when the sun was the single dominant

interferometric cross-correlation products

radio source in the daytime sky. The data

AAVS1 is primarily a test and verification

(the "visibilities") can be generated between

showed:

system aimed at:

all antennas for a single (~1 MHz wide)

providing on-the-ground experience

coarse channel using the internal GPU-based

in deploying, commissioning and

correlator. Alternatively, raw voltage data

maintaining SKA-Low hardware and

for a single coarse channel for all antennas

software;

can be written to disk for short (~2 seconds)

verifying the proposed station-level

bursts.

stations as part of the SKA telescope will be

and visibility data. 4.

Verifying that the station can be

station beams, AAVS1 is a standalone system

calibrated using a sky model that

that is being used for verification, so most of

incorporates the sun and diffuse

the characterisation work for AAVS1 thus far

background sky.

has been performed by using the station as a standalone 256 antenna interferometer. The

The second and third items in the bootstrap

activities have thus been following a series of

list above were achieved by manually forming

steps to "bootstrap" the system from initial

visibilities with 32 "fine" spectral channels

deployment (where we know nothing about

from a few seconds of captured (single coarse

the system) to full station beam.

channel) raw voltage data, then converting the visibilities to a standard radio astronomy

correct. •

The bootstrapping process broadly consists

level beamforming against SKA

of:

sensitivity specifications;

1.

delays in the system, which would have

2.

Checking signal level and normalising Verifying that there are no large unanticipated/uncorrected delays between signal paths in the station. (This

The existing system has been in the field at

is an assumption/requirement associated

the Murchison Radio-Astronomy Observatory

with forming station beams at the

(MRO) for over 12 months now, showing very little issues. The field hardware, as well as the hardware located at the CPF, has showed reliable operations.

20

ASTRON News / Winter 2018

slopes over the coarse channel. •

the power levels for each antenna.

shaking down core station-level and beamforming.

There were no large uncorrected manifested themselves as a large phase

verifying the performance of station-

software and firmware for calibration

Some antennas had their polarisations swapped.

commissioning and calibration plan; •

Signal path mappings were mostly

The digital coarse channel bandpass qualitatively looks as expected.


A "first image" The data described above were used to create an all-sky image with the Sun as the dominant compact source at the phase centre. Towards quantifying calibration accuracy and stability After the initial bootstrap, the internal station GPU-based correlator was used to generate visibilities from a single coarse channel for many hours to test both the stability of the system and the ability of various calibration schemes to use the diffuse galactic sky to calibrate the station. Daytime data from the southern autumn were particularly useful for diagnostic use. Example calibration solutions from a 2-hour dataset using the sun as a calibrator are shown in figure 2.

Figure 1: The image shows the first image made by AAVS1 using approximately 2 seconds of data centred on 160 MHz. The image is the XX polarisation using robust -0.5 weighting, all baselines and light (niters=2000) cleaning. The sun is at RA/DEC 1.4/9.3, which is the phase centre of the image. (Note for scale, the sun has been assigned as a 10000Jy source. The intensity scale at the bottom deliberately burns out the sun so that other features can be seen.) Since the image is a snapshot, is has a slant orthographic projection such that the coordinate system is accurately represented by ds9 in this view. As well as the sun, two other radio sources are clearly visible: Fornax A and the LMC. Eagleeyed readers will also spot the SMC and PKS2356-61.

24-hour datasets were collected in May, June and July. Using the calibration solutions from daytime data, the full 24-hour dataset was imaged at 1-minute intervals. An example snapshot image is shown figure 3.

Figure 3: A zenith-pointed all-sky image at 160 MHz from AAVS1. The compact station is sensitive to the large-scale diffuse emission from the Galactic plane, which is clear in this image. Also visible are several "A-team" radio sources including CenA, VirA, HydA and TauA. Figure 2: this image shows example phase solutions from a 2-hour 160 MHz dataset using antenna 2 as the reference. The solutions are generally flat with small deviations on ~20-minute timescales.

ASTRON News / Winter 2018

21


In order to estimate the stability of the station calibration over time, a statistical analysis of the calibration solutions was performed for different datasets (daytime, night-time) and calibration schemes. Each solution dataset was divided in 10-minute bins, which is the timescale employed as update rate in the SKA-low station

Figure 4: This plot shows the drift in the phase solutions in 10-minute bins calculated for the 2-hrs observation carried out on 2018-11-08 centred on the solar transit.

calibration. For every sample, the variation of the phase and amplitude solutions, relative to the beginning of each 600-s interval, was calculated for every antenna. Figure 4 shows an example of phase difference distribution calculated for the 2018-11-08 solar observation, in particular the channel corresponding to 160 MHz of observed frequency, in the XX polarisation. Here the calibration solutions were obtained using a

Figure 5: Drift in the amplitude solutions in 10-minute bins calculated for the 2-hrs observation carried out on 2018-11-08 centred on the solar transit.

sun-based calibration scheme. The plot of the amplitude variations of the same complex solution set is shown in figure 5. Also, for other observations and frequencies, as in this case, the calibration solutions in YY polarisation seem to be less stable than the XX one, in both amplitude and phase. This behaviour needs to be further investigated.

22

ASTRON News / Winter 2018

Figure 6: Maximum standard deviation of the phase cal solutions at 160 MHz within 600s bins measured during the 2018-11-08 solar observation for the XX (blue diamonds) and YY (red dots) polarisations.


Slow, slower, slowest... The LOFAR Tied-Array All-Sky (LOTAAS) survey has discovered a new, record-breaking, radio pulsar. The pulsar, PSR J0250+5854, is the slowest spinning radio pulsar known, rotating once every 23.5 seconds. The detection of radio emission at such long spin periods challenges conventional pulsar emission models.

which predict that radio emission can no longer

Due to its long spin period and very short duty

be generated if a pulsar spins too slow.

cycle - the pulse is only on for 0.4% of a rotation - finding pulsars like PSR J0250+5854 is very

Due to the slow spin period of the pulsar, we

difficult. The hour-long LOTAAS observations

were able to detect its pulsations in imaging data

make this survey exceptionally well-suited to find

from the LOFAR Tier-1 imaging survey (LOFAR

similar pulsars, and we are planning to reprocess

Two-metre Sky Survey, LoTSS). We did this by

the survey data using fast-folding algorithms,

selecting or deselecting those 1-second visibilities

which have better sensitivity to long period

that contain the pulsed emission, and use the

pulsars compared to traditional Fourier based

visibilities to create images in which the pulsar

periodicity searches.

is present or absent as a radio point source. With this approach we achieved a sub-arcsecond

These results have been published in Tan et al.

localisation of the pulsar.

(2018, ApJ 866, 54).

Cees Bassa (bassa@astron.nl) on behalf of Chia Min Tan and the LOTAAS team. Following the 2015 visit of King WillemAlexander to China, the Chinese and Dutch space agencies (CNSA and NSO) agreed to support a Dutch scientific radio astronomy payload, the Netherlands China Low Frequency Explorer (NCLE) on board the Chinese Changâ&#x20AC;&#x2122;e 4 relay satellite. At the so-called L2 point behind the Moon, this satellite will act as a communication relay station between Earth and the Changâ&#x20AC;&#x2122;e 4 lunar far-side lander and rover, to be launched later this year. LOFAR is performing a survey of the Northern sky for pulsars and fast radio bursts. Amongst its recent discoveries is PSR J0250+5854, which was discovered through the harmonics of its fundamental spin period of P = 23.535 seconds. This spin period is 2.8 times longer than the previous slowest spinning radio pulsar, challenging some of the pulsar emission theories,

Figure 1: The radio emission of PSR J0250+5854 is only visible for a fraction (0.4%) of its 23.5-second spin period. The two insets show the LOFAR Tier-1 imaging survey data when selecting those 1-second visibilities that either do (on), or do not (off), contain the pulsed emission.

ASTRON News / Winter 2018

23


Westerbork Radio Telescope’s major upgrade enlargers field of view 37 times With an innovative new type of receiver, called Apertif, the field of view of the Westerbork Synthesis Radio Telescope in the Netherlands has been increased 37 times. Apertif, developed by ASTRON, was officially opened on 13 September 2018 by deputy Cees Bijl of the Drenthe province. On this day the 50-year anniversary of the telescope was also being celebrated. Iris Nijman, Roy van der Werp The iconic 50-year old Westerbork Synthesis Radio Telescope (WSRT) has been upgraded with a new high-speed, wide-field radio camera called Apertif. Using a technique called beamforming, 12 of the 14 dishes are now able to map a part of the sky that is 37 times larger than before. Apertif is also a pathfinder of the Square Kilometre Array (SKA), the future largest and most sensitive radio telescope in the world, recognised by the SKA project. Evolution of galaxies Apertif will map a big part of the northern sky to make radio images of the neutral hydrogen gas in the Universe, providing a unique and new view of the properties and distribution of gas in galaxies. It will also look at a smaller part of the sky in much more detail, giving

24

ASTRON News / Winter 2018

us a sharper picture of very faint, nearby

Institute-wide effort

galaxies, as well as galaxies in the very distant

The upgrade of Westerbork has been an

Universe. These two surveys will lead to new

institute-wide effort for ASTRON. “To develop

insights into the formation and evolution of

a complex instrument such as Apertif, many

galaxies. The collected data will be used by

people from multiple disciplines have to

future researchers for decades to come.

collaborate closely,” says project leader Agnes Mika. “That’s why engineers from different

The exploding Universe

departments have been working together in

The upgraded telescope will also search for

one room for more than a year. This improved

the most powerful explosions in the Universe,

the communication and problem-solving

called Fast Radio Bursts (FRBs). The origin and

significantly. I am very proud of the whole

nature of these extremely bright flashes of

team, and happy to see Apertif become

radio light, that travel billions of light years to

operational.”

reach Earth, are still largely a mystery. Because the flashes last only a fraction of a second, they are very easy to miss and difficult to observe. This is going to change with Apertif, which will continuously make a high-speed movie of the radio sky that will be analysed by the most powerful GPU-supercomputer in the Netherlands.


Book 50 years Westerbork To capture the rich history of the WSRT, the book "50 years Westerbork Radio Observatory. A continuing journey to Discoveries and Innovations", released during the opening of Apertif. During the Apertif opening, Arnold van Ardenne, as chief editor, presented the book. The book is dedicated to Ger de Bruyn, whoâ&#x20AC;&#x2122;s untimely passing away left a hole, as champion user, science visionary and great personality. Among the 18 chapters of the book is a chapter which captures a large part of Ger's "personal discovery table" ranging from 1970 to 2015. We are very proud that we now have described and illustrated the rich history of the WSRT. Making this book would not have been possible without the editors Arnold van Ardenne, Richard Strom, Steve Torchinsky and the help of everybody involved.

ASTRON News / Winter 2018

25


The origin of the gamma-ray binary 1FGL J1018.6-5856

in total). We also determined the distance

system. And more importantly, it excludes the

to 1FGL J1018.65856 to be about 6.4 kpc.

physical relation of the binary system with the

Together with the radial velocity of the source

supernova remnant G284.3-1.8, as it had been

we computed its three-dimensional proper

speculated in the past (Marcote et al. 2018,

and peculiar motion within the galaxy. We

A&A, 619, A26).

obtained a peculiar motion of 1FGL J1018.65856 of u = 45 +30/-9 km s-1, with the system

The determination of the 3D motion from this binary allowed us to unveil its origin and evolution within the galaxy.

moving away from the galactic plane. The obtained motion and distance allowed us to estimate a mass loss of 4 < Î&#x201D;M < 9 solar mass during the core collapse that lead to

Benito Marcote (marcote@jive.eu)

the creation of the compact object in the

Gamma-ray binaries are systems composed of a massive star and a compact object (likely a young non-accreting neutron star in all cases) that exhibit emission from radio to very high-energy gamma rays. We studied the radio emission of the gamma-ray binary 1FGL J1018.6-5856 for the first time at milliarcsecond scales to constrain the emitting region and determine its peculiar motion within the galaxy to clarify its origin. We analysed an observation of 1FGL J1018.65856 performed with the Australian Long Baseline Array (LBA) at 8.4 GHz to obtain an accurate astrometry of the system and study its emission on milliarcsecond scales. The data was combined with the optical Gaia DR2 and UCAC4 catalogues to consolidate the astrometry information therein. We detected compact radio emission (<3 mas or <20 AU), implying a brightness temperature of >5.6¡106 K, and confirming its non-thermal origin. This emission is consistent to the one observed in other gamma-ray binaries. Our research showed consistent results between the proper motion published by Gaia DR2 and the positions obtained from the Gaia DR2, UCAC4, and LBA data (spanning 20 year

26

ASTRON News / Winter 2018

Figure 1: The high resolution image of 1FGL J1018.6-5856 (top right) allowed us to determine its peculiar motion within the Galaxy. The other images show the relative motion of the binary (blue and red arrows) with respect to the Sun and the SNR G284.3-1.8 (red circle on the left, and extended emission on the right bottom map).


SWENED collaboration Dutch organisations active in the field of Space Weather united in SWENED.

On 19 September at the third SWENED

- S&T BV

meeting, hosted by the KNMI, a Memorandum

- TriOpSys BV

of Understanding has been signed to

- Fugro-Intersite BV

emphasise the relevance of such a network

- Agentschap Telecom

organisation. This signing took place behind

- Kadaster

not-just-a-desk; it used to be the desk of Christophorus Buys Ballot. Buys Ballot founded the KNMI in 1854 with the aim to provide weather forecasts and warnings on a scientific

Gert Kruithof (kruithof@astron.nl)

basis. Nowadays, attention is paid to space weather as well.

The aim of the Dutch network organisation SWENED is to exchange information and

The partners in SWENED are:

building knowledge regarding space weather,

- KNMI

to discuss possible projects, opportunities

- ASTRON

and innovation. The partners in SWENED

- Joint Meteorological Group

also intend to collaborate and to stimulate

- TU Delft

the cooperation with foreign space weather

- CWI

centres and other international networks.

- NLR

Figure 1: Signing of the MoU by the SWENED partners on 19 September 2018.

ASTRON News / Winter 2018

27


Achievements of the CITT2 The CITT2 projects combined the research of new calibration and imaging algorithms to the need of providing to general astronomers a processing pipeline able to produce thermal noise limited images from HBA LOFAR data.

For HBA data, the team has transformed a

in the data by the ionosphere and (for the first

collection of scripts performing direction

time) model them in the various steps of the

independent and direction dependent

signal processing (de Gasperin et al. 2018, in

calibration (van Weeren et al. 2016) into two

press). The correction of ionospheric effects

pipelines: prefactor (Pre-facet calibration

during an imaging step was made for the first

for LOFAR) and FACTOR (Facet Calibration

time by applying a TEC-screen to the a-term

for LOFAR). Both available in the ASTRON

in WSclean+IDG. This has shown significant

github repository. The direction independent

improvements on real data images, opening

calibration isolates the instrumental from the

the possibility to fully calibrate the LBA. After

ionospheric contribution to the signal, while

three years of activity the CITT2 project has

the direction dependent pipeline corrects for

concluded. Its results will be implemented in the

the residual phase errors introduced by the

Radio Observatory production system through a

ionosphere and frequency and time beam

new project called Science Delivery Framework.

Emanuela Orru’ (orru@astron.nl)

variations.

The project will also include a discussion forum

The Calibration and Imaging Tiger Team

For LBA data, extensive research has been

project (CITT) arose from the requirement

performed to understand the effects introduced

where the development of advanced algorithms for LOFAR data reduction will continue.

to produce thermal noise limited LOFAR images ready for science exploitation. The calibration and imaging software packages that are commonly used in radio astronomy do not accurately represent instrumental and ionospheric effects characteristic of the LOFAR telescope and its frequency regime (e.g. ionosphere and frequency and time variable beam pattern). The goals of CITT2 were: • Development of a pipeline able to provide HBA thermal noise limited images to the users on the Radio Observatory production system • Research and development of algorithms for calibrating LBA data. The team was composed of people with different expertise: astronomers, experts on ionosphere, algorithm developers and pipeline developers. To achieve the goals, the CITT2 worked on improving the processing efficiency and algorithm precision of basic software elements for calibration and imaging, such as DPPP (Default Preprocessing Pipeline), and WSClean+IDG (W-Stacking Clean+Image Domain Gridding).

28

ASTRON News / Winter 2018

Figure 1: The cluster of galaxies CIZA J2242.8+5301 (Hoang et al. 2017, right) obtained using prefactor and FACTOR


The duty cycle of the radio galaxy B2 0258+35

implies that the large-scale lobes are not likely

This study will provide a reference point for

to be very old remnants but are probably still

the characterisation and interpretation of low

fuelled by the nuclear engine or the jets have

surface brightness lobes associated to radio

switched off no more than a few tens of Myr

galaxies detected in the LOFAR survey.

ago. These results are presented in Brienza et al. (2018).

Marisa Brienza, Raffaella Morganti (m.brienza@ira.inaf.it) Radio loud Active Galactic Nuclei (AGN) cycle through periods of activity and quiescence. Sometimes we are lucky enough to observe the remnant plasma of a previous phase of jet activity together with a new pair of restarted jets. Using these so-called â&#x20AC;&#x153;restarted radio galaxiesâ&#x20AC;?, we can study the timescales of the jet duty cycle, which are to date still poorly understood despite their relevance for the overall galaxy evolution process. In this work we have investigated the duty cycle of the restarted radio galaxy B2 0258+35, which consists of a pair of kpc-scale jets embedded in two large-scale lobes (240 kpc) with relaxed shape and very low surface brightness that resemble remnants of a past AGN activity. Thanks to its unprecedented sensitivity at low frequencies, LOFAR has allowed us to investigate the outer lobes at 150 MHz (see Figure 1 on the right). Combining these data with available WSRT data at 1400 MHz (see Figure 1 on the left) and new observations

Figure 1: Radio maps of the source B2 0258+35. Left: WSRT contours at 1400 MHz by Shulevski et al. (2012) overlaid on the SDSS optical image. The inset shows the source at high resolution at 5 GHz (Giroletti et al. 2005). Right: LOFAR map at 150 MHz.

with the Sardinia Radio Telescope at 6600 MHz, we managed to investigate their spectral properties over a very broad frequency range and constrain their age. Interestingly, their spectrum is not ultra-steep (spectral index 0.5-0.7) or significantly curved as expected for an old ageing plasma. This

ASTRON News / Winter 2018

29


Dwingeloo telescope downloads image of Lunar far side and Earth

downlink signal, and we have measured

Figure 2 is the result of a very nice

lunar reflections of the signal. Correlating

collaboration between MingChuan Wei

the latter with the original signal gives some

(Harbin Institute of Technology), Reinhard

information about the lunar surface. Reports

Kuehne, Daniel Estevez and the authors of this

of these experiments can be found at https://

article.

destevez.net/tag/dslwp/ The mission is still ongoing. We have made a time lapse sequence of the Earth rising from behind the Moon, and are planning lunar occultation experiments.

On 10 October 2018, the Dwingeloo telescope helped downloading an image of the Lunar far side and Earth. The image was taken by a Chinese lunar orbiting satellite. Tammo Jan Dijkema, Cees Bassa, Paul Boven The satellite that took this picture was launched in May together with the larger satellite Changâ&#x20AC;&#x2122;e 4 that also carries the The Netherlands-China Low-Frequency Explorer (NCLE) payload built by ASTRON, the Radboud Radio Lab and ISIS. Changâ&#x20AC;&#x2122;e 4 will stay around the L2 point behind the moon, while the much smaller DSLWP-B (Discovering the Sky at Longest Wavelengths Pathfinder) is in an elliptical orbit around the moon. One of the DSLWP-B payloads is an amateur radio (UHF/ VHF) module developed at Harbin Institute of technology, which includes a small camera. To download images, an antenna with high sensitivity is needed, which is why CAMRAS was asked to use the Dwingeloo telescope as one of the main ground stations of the amateur radio payload. Other experiments we have done with DSLWP-B use the radio signal: we have performed VLBI experiments with the

30

ASTRON News / Winter 2018

Figure 1: The DSLWP satellite, about 50cm high. Indicated are the UHF/VHF antennas and camera. Credits: MingChuan Wei, Harbin Institute of Technology.


Figure 2: The image taken on 9 October 2018. Credits: MingChuan Wei, Harbin Institute of Technology. Colours adjusted.

ASTRON News / Winter 2018

31


LOFAR strides towards being a truly multitasking radio telescope Thanks to its new brain COBALT 2.0, LOFAR would be able to carry out simultaneous observations for several science cases, thus boosting the science returns per observing hour. In addition to carrying out the above multi-mode observing termed LOFAR Mega Mode (LMM), COBALT 2.0 can do significantly better. COBALT 2.0 is future proof in terms of its design but is also amongst the most energy efficient (greenest) HPC correlators that can be developed with the current technology. V.N.Pandey (ASTRON/RUG) (pandey@astron. nl), Jan David, Cees Bassa,, Jason Hessels, Rene Kaptijn on behalf of COBALT 2.0 team. The central theme behind the LMM is to upgrade the existing COBALT 1.0 correlator, which receives the signals from LOFAR stations spread across Europe, and combine them in real time to produce astronomical data. The main challenge was to come up with an optimal design for the new correlator COBALT 2.0, capable enough to simultaneously deliver data for several science cases (e.g. imaging and beam-forming). The correlator of a radio telescope is a real time 24x7 instrument and arguably,

32

ASTRON News / Winter 2018

the most important component that has

help to further reduce the total power

critical impact on the entire operation. The

consumption.

COBALT 2.0 team took this task head-on by

Together, the production nodes have a

successfully coming up with an optimised

capacity of receiving and processing data from

configuration involving the most appropriate

more than 130 LOFAR stations (LBA+HBA). The

set of components, GPUs, CPUs, technologies

excess compute power can also be used for

and network topologies. Due to their smart

data quality improvements like high time and

work, the resulting COBALT 2.0, currently

frequency resolution RFI excision as well as

under procurement via a rigorous and a

new modes of observation.

very successful tender process, can deliver performance more than twice of the LMM

We expect to receive the correlator hardware

requirements.

shortly and are looking forward to the next stage of the challenging but exciting

COBALT 2.0 will consist of 13 production nodes

commissioning period. This would mark a

with a total of 63 TFLOPS CPU compute power

giant step towards LMM operations. And most

and 360/180 TFLOPS (single/double precision)

importantly, the increased efficiency of LOFAR

of GPGPU compute power. Each production

can lead to many more scientific discoveries in

node is a highly balanced system consisting of

the years to come.

highly energy efficient components available two Intel Xeon Gold Skylake SP 6140 (18 core)

The COBALT 2.0 team would like to thank the

CPUs and two NVIDIA Tesla tensor core V100

external referees for their critical reading and

GPUs. The Platinum grade power supplies

useful comments on the tender document.


ASTRON News / Winter 2018

33


HI absorption workshop 2018

online on the webpage of the workshop (http:// www.astron.nl/hiabsorption2018/programme. php) We were particularly proud of the almost

HI absorption offers a unique tool for studying all kinds of objects in the universe. Thanks to upcoming largescale surveys, we are about to use it to greatly expand our knowledge of the gas distribution and dynamics in galaxies.

perfect gender balance among the participants coming from all over the world and of the large fraction of talks from postdocs and PhD students. The feedback from the participants was overwhelmingly positive and we agreed to organise this type of workshop again next year at another institute.

Raffaella Morganti (morganti@astron.nl) Robert Schulz (schulz@astron.nl) Following the successful first meeting in 2017, we hosted a second workshop “HI absorption 2018” at ASTRON on 29-31 August 2018, to coordinate the efforts of the various survey teams (from ASKAP, MeerKat, Apertif and GMRT) and exchange expertise and software tools. Updates on the preparations of the HI surveys showed the first interesting results from the commissioning work. The science talks covered again a wide range of topics from HI at lowand high redshift, associated and intervening absorption, large-area low-resolution surveys and high-angular resolution studies with VLBI. This time, one of the focal points of the meeting was synergies with optical spectroscopic and imaging surveys such as the ones planned with WEAVE (the integral field spectrograph to be installed at the WHT) as well as the imaging surveys planned by the JPAS group on the new Observatorio Astrofísico de Javalambre in Spain. A significant amount of time at the end of each session was dedicated to discussions and a special discussion session was devoted to prospects with the SKA. Notes from the fruitful discussions as well as the talks are available

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ASTRON News / Winter 2018

Figure 1: Group picture of the participants of the HI absorption workshop.


Symposium The new era of multi-messenger astrophysics The era of multi-messenger astrophysics has dawned. The recent developments in astrophysical neutrinos and the detection of gravitational waves generated by merging neutron stars have demonstrated the importance of multi-messenger observations to understand the complexity of the dynamic sky.

ASTERICS Symposium 25-29 March 2019 Groningen, The Netherlands

The New Era of Multi-Messenger Astrophysics

Giuseppe Cimo, (cimo@jive.eu) Since 2015, the Horizon 2020 ASTERICS

CONFIRMED INVITED SPEAKERS

SCIENTIFIC ORGANISING COMMITTEE

collaboration, coordinated by ASTRON,

Imre Bartos - University of Florida (USA)

Gemma Anderson - Curtin University (Australia)

has successfully worked to foster the

Elisa Bernardini - DESY (Germany)

Dipankar Bhattacharya - Inter-University Centre for Astronomy and Astrophysics (India)

Giancarlo Ghirlanda - INAF, Brera Astronomical Observatory (Italy)

Marica Branchesi - INFN (Italy)

Piotr Homola - Institute of Nuclear Physics PAS (Poland)

Eric Chassande-Mottin - CNRS, APC (France)

multi-messenger facilities. Now, ASTERICS,

Samaya Nissanke - University of Amsterdam (Netherlands)

Alessandra Corsi - Texas Tech University (USA)

together with ASTRON and the University of

Judith Racusin - NASA/GSFC (USA)

Anna Franckowiak - DESY (Germany)

interoperability of multi-wavelength and

Aart Heijboer - Nikhef (Netherlands)

Groningen, is organising the symposium "The New Era of Multi-Messenger Astrophysics" with the goal to explore new methods for multi-messenger science and the related

Mansi M. Kasliwal - California Institute of Technology (USA)

KEY THEMES

the recent developments in the fields of

Alert mechanism systems and fast response of facilities

The conference will be held in Groningen, the Netherlands, from 25 to 29 March 2019. Registration is open. Please find all the

Zsolt Paragi - Joint Institute for VLBI ERIC (Netherlands)

Sources of high-energy particles Multi-messenger technology and interoperability

and the highly energetic dynamic sky.

Tara Murphy - University of Sydney (Australia)

Gravitational wave sources in multi-messenger signals

research infrastructures, and to cover gravitational waves, astrophysical neutrinos

Sera Markoff - University of Amsterdam (Netherlands)

Electromagnetic transients in multi-messenger signals

Fabio Pasian - INAF, Astronomical Observatory of Trieste (Italy) Enrico Ramirez-Ruiz - University of California, Santa Cruz (USA) Patrick Woudt - University of Cape Town (South Africa)

The principles of Open Science

Feng Yuan - Shanghai Observatory (China)

multi-messenger.asterics2020.eu Horizon 2020 The EU Framework Programme for Research and Innovation

Image credits (from left to right): CTA ASTRON, DESY/Ralf Wischnewski ESO, SKA, KM3Net

ASTERICS is a project supported under grant agreement n. 653477

relevant information on the conference website: http://multi-messenger.asterics2020. eu/

ASTRON News / Winter 2018

35


ASTRON is the Netherlands Institute for Radio Astronomy. Our mission is to make discoveries in radio astronomy happen. We do this by the development of new and innovative technologies, the operation of worldclass radio astronomy facilities, and the pursuit of fundamental astronomical research. Engineers and astronomers at ASTRON have an outstanding international reputation for novel technology development, and fundamental research in galactic and extra-galactic astronomy. ASTRON is part of the institutes organisation of NWO. Office address: Oude Hoogeveensedijk 4 7991 PD Dwingeloo The Netherlands Postal address: P.O. Box 2 7990 AA Dwingeloo The Netherlands Phone +31 521 59 51 00 Fax +31 521 59 51 01 pr@astron.nl www.astron.nl @ASTRON_NL facebook.com/ASTRON.NWO

Winter 2018

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ASTRON News / Winter 2018

ASTRON News Winter 2018  
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