Are you the publisher? Claim or contact us about this channel


Embed this content in your HTML

Search

Report adult content:

click to rate:

Account: (login)

More Channels


Channel Catalog


Channel Description:

A daily view of all the goings-on at ASTRON and JIVE.
    0 0

    © Anne Archibald

    We carried out a test of Einstein's theory of gravity with the millisecond pulsar in a stellar triple system. We showed that the pulsar and its inner white dwarf companion experience accelerations that differ by no more than three parts in a million. This is a summary of the Nature paper. There's also a nice News and Views article by Clifford Will.

    0 0
  • 07/16/18--17:00: Scaling SAGECal to SKA
  • © Hanno Spreeuw

    SAGECal [1, 2] has been designed to meet not only the challenges of calibrating present-day radio telescopes like LOFAR, but also to handle the data rates of telescopes under construction, like Square Kilometre Array (SKA). To validate this, we have developed new GPU accelerated code and measured the times Sagecal needs to predict the sky and beam for five artificial data sets, having 64, 128, 256, 384 and 512 stations and for five numbers of sources. The size of these datasets obviously increases with the square of the number of stations (N) since the number of baselines equals 0.5xN(N-1). In this figure we depict sky plus beam prediction times for both the CPU as well as the GPU version of Sagecal. For this research, we have used a cluster node equipped with two CPUs (2x Xeon E5-2660v3, 40 logical cores) and a Titan-X (Pascal) GPU on ASTRON's DAS5.

    Both versions depend quadratically on the number of stations, but the GPU version is about ten times faster. In this research, we have explored GPU utilisation and latencies to improve Sagecal performance. We have reduced latencies in the two most important kernels. Our future work involves optimization of a number of other kernels within Sagecal, including the kernels that do the actual calibration.

    References

    [1] S. Yatawatta, S. Kazemi, and S. Zaroubi. GPU accelerated nonlinear optimization in radio interfer-

    ometric calibration. In 2012 Innovative Parallel Computing (InPar), pages 1–6, May 2012.

    [2] https://github.com/nlesc-dirac/sagecal


    0 0

    © ASTRON

    On Friday 6 July 2018 at 10:25am (CEST), LOFAR fully automatically responded to an astrophysical transient source for the very first time. A bight burst of gamma-rays, known as GRB 180706A, was detected by the Neil Gehrels Swift Observatory and the satellite automatically sent an urgent message to waiting facilities on the ground. In the graph at the top of the figure, the black data points show the initial flash of gamma-rays and the blue data points are the follow-up X-ray observations obtained by the satellite.

    LOFAR responded to the rapid trigger alert and a 2 hour observation started within 5 minutes of the alert. The box at the bottom of the figure shows the LOFAR monitoring system receiving and observing this source. As shown by the red shaded region, these observations cover the entire 'plateau' phase in the X-ray observations and the origin of this phase is still hotly contested for these events. Our observations may hold invaluable clues to show what is happening during this phase.

    This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.


    0 0

    © ESO

    Prompted by the recent approval of a study to investigate options for developing the ALMA Observing Tool, a workshop was held at the European Southern Observatory in Garching on 4-6 June 2018. This brought together groups working on proposal submission tools at observatories around the world to review the current status of proposal submission systems, exchange knowledge and experience of recent developments in hardware and software solutions and to explore prospects and plans for the future development of tools and possible cooperation.

    ASTRON presented its experiences with Northstar over the last 14 years for both WSRT and LOFAR and our cooperation with many other observatories: JIVE/EVN, e-Merlin, Effelsberg, Onsala, OHP, Yebes, OPTICON, WHT/INT, JCMT, UKIRT. ASTRON was represented by Hanno Holties (not in the picture), Sander ter Veen and Adriaan Renting.


    0 0

    © None

    On the morning of an overcast and (very) windy day in June, a group of tough ASTRON and NOVA gents and lads were gathering with chattering teeth on the beach of Workum. Curious about what they were doing there? Read on - this is their story.

    So, they were standing on the beach, feeling lost and cold. All of a sudden a truck arrived, disgorging wetsuits, impact vests and helmets. Half an hour later, looking like men (and women) from Mars, in identical pink shirts, these brave people were ready for their first trial: learning to control power kites that did not want to be controlled. Once they have mastered this skill, they were ready for the second trial of the day: taming (much) bigger kites in knee-deep water.

    Ater a break and a bite to lift their spirits, our heroes ventured into the water again for their third test: body drag and upwind body drag. For the lucky ones this meant being dragged through the water by a powerful kite that had to be steered with only one hand. For the unlucky ones it involved gulping down massive amounts of water or skipping on the surface of the Ijsselmeer like flat stones.

    Those who mastered these skills were allowed to proceed to the next stage: learning to get on a board and to stay on a board. Faults were promptly punished by either falling on one's bottom or being catapulted to what felt as significant heights. The bravest and most skilled champion managed to glide for a full thirty metres, while others had to be satisfied with a meager two to three metres.

    At the end of the day, our tired but satisfied heroes were rewarded with a delicious barbecue on the beach in a very "gezellig" atmosphere (if you don't know what "gezellig" means, you should remedy it quickly - it is by far the most important Dutch word!).

    This story couldn't have been written without the contributions of Antix Sports and the ASTRON/JIVE PV.