Matthew Strong

VLBI_UDP: An application for transporting VLBI data using the UDP protocol

This paper describes the VLBI_UDP application, which has been designed to transport astronomical data recorded via a technique known as Very Long Baseline Interferometry (VLBI), using the UDP protocol. The design of the VLBI_UDP application is discussed together with modifications that provide additional features such as file access and packet dropping. Network tests of the application show that the application is stable and correctly deals with packets lost on the network. Correlation tests using data with deliberately dropped packets show that the correlation process is resilient under data losses approaching 20% and that the resulting correlation amplitude decreases as 1.2 times the packet-loss rate. The results also indicate that while the correlator is able to cope with at least 2 consecutive missing headers, it needs to see at least 2 correct headers, otherwise synchronisation is lost.

The contribution of ESLEA to the development of e-VLBI

e-VLBI the use of the Internet in real time VLBI high resolution observations in radio astronomy has become a routinely available technique in this last year. ESLEA has contributed significantly to its development, by improving our understanding of data transmission networks, the limitations of transport protocols and end hosts, and communication of this knowledge to radio astronomers in Europe. A series of tests, organised by JIVE in the Netherlands and ESLEA has gradually led to open call science runs, now considered as a regular part of European VLBI Operations. A major upgrade project EXPReS is now underway to equip more European observatories with e-VLBI capability. This paper outlines the work done in ESLEA on e-VLBI and illustrates its success by showing recently obtained astronomical results.

Investigating the e-VLBI Mark 5 end systems in order to optimise data transfer rates as part of the ESLEA project

We report on the development of high bandwidth data transfers for e-VLBI at Jodrell Bank Observatory as part of the ESLEA project. ESLEA is a UK project to exploit the use of switched-lightpath optical networks for various app lications, including e-VLBI, HEP, High Performance Computing and e-Health. We show how the CPU power of the Jodrell Bank eVLBI Mark 5A end systems was limiting the data tran sfer rate to below 512 Mb/s. Both of the Jodrell Bank Mark 5A end systems have now been upgr aded and can now transfer e-VLBI data to JIVE at the required data rate of 512 Mb/s.

Trans-Atlantic UDP and TCP network tests

A VLBI trans-Atlantic connection would greatly extend the resolution of capabilities of eVLBI. So far igrid 2005 and SC 2005 saw the first UKlight connection to the US via Chicago. We report on UDP and TCP network tests performed between Jodrell Bank Observatory, UK, and Haystack Observatory, USA, utilising the UKLight dedicated lightpath, provided by the ESLEA project, to the Starlight connecting node in Chicago. We show near linerate instantaneous UDP throughput over this lightpath, and IPerf TCP bandwidths in excess of 900 Mbps.

A possible radio supernova in the outer part of NGC 3310

As part of an ongoing radio supernova monitoring program, we have discovered a variable, compact steep spectrum radio source ∼65 arcsec (∼4 kpc) from the centre of the starburst galaxy NGC 3310. If the source is at the distance of NGC 3310, then its 5-GHz luminosity is ∼3 × 10 19 W Hz -1 . The source luminosity, together with its variability characteristics, compact structure (< 17 mas) and its association with a group of H ii regions, leads us to propose that it is a previously uncatalogued Type II radio supernova. A search of archival data also shows an associated X-ray source with a luminosity similar to known radio supernova.

First observations of GRS 1915+105 with e-VLBI

A. Rushton ,1 R. E. Spencer,1 M. Strong,1 R. M. Campbell,2 S. Casey,1 R. P. Fender,3 4 M. A. Garrett,2 J. C. A. Miller-Jones,4 G. G. Pooley,5 C. Reynolds,2 A. Szomoru,2 V. Tudose4 6 and Z. Paragi2 1The University of Manchester, Jodrell Bank Observatory, Cheshire SK11 9DA. 2Joint Institute for VLBI in Europe, Postbus 2, 7990 A A Dwingeloo, The Netherlands. 3School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ Southampton, UK. 4“Anton Pannekoek” Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands. 5University of Cambridge, Mullar Radio Astronomy Observatory, J. J. Thomson Avenue, CB3 0HE Cambridge, UK. 6Astronomical Institute of the Romanian Academy, Cutitul de Argint 5 RO-040557 Bucharest, Romania

Results from e-EVN observations of GRS 1915+105

We present results from the first successful open call e-VLBI science run, observing the X-ray binary GRS 1915+105. e-VLBI science allows the rapid production of VLBI radio maps, within hours of an observation rather than weeks. A total of 6 telescopes observing at 5 GHz across the European VLBI Network (EVN) were correlated in real time at the Joint Institute for VLBI in Europe (JIVE). Throughout this, GRS 1915+105 was observed for a total of 5.5 hours, producing 2.8 GB of correlated visibility data. The peak brightness was 10.2 mJy beam−1, with a total integrated radio flux of 11.1 mJy.