Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/management/atuc/2006jun/docs/3.5_LBA.pdf Дата изменения: Fri Jun 2 04:58:07 2006 Дата индексирования: Sun Jun 27 03:11:36 2010 Кодировка:

ATNF ATUC ME MO RANDUM To: From: Date: Subject: 1) Operations In the past 6 months there were 2 major LBA observational sessions, 8-17 March and 11-17 May. No major tec hnic al problems were reported from any observatory. The disk-bas ed VLBI recording system and soft ware correlation at Swinburne has been increasingly replacing S2 tape-based observations. In the May session only 2 x 12h observations were rec orded on tape. The transition to disk systems is currently limited only by disk availabilit y. Two of the H-masers that hav e been showing problems were refurbished in March by visiting Russian experts. It is planned that 3 more H-mas ers will be refurbished in the next financial year. All observ ational set ups on the LBA now include real-time fringe testing on the Swinburne correlat or. This has greatly improv ed the reliability of the LBA. The scheduling of LBA observ ations has been streamlined. Communications and information exchange is now via Web Wiki pages and this has greatly improved LBA operations and observing documentation. 2) 2005 LBA statistics Overall the LBA ac hiev ed a 94.5% success rate, about 2% improv ement on the previous year, to a large extent due to the succes s of real-time fringe checking. Most of the telesc opes continued with succ ess rat es over 97%, and the Park es 6% failure rate was mostly due to high winds (4.8%). A summary is giv en in the tables below.
Telescope Hours obs % success Parkes 332 94 ATCA 334 98 Mopra 33 4 97.5 Hob 31 8 97 C ed 27 2 97. 5 Tid 50 100 H a rt 114 99 Kokee 48 100 Shang 17 100 LBA 346 94. 5

ATUC Tass o Tzioumis 1 June 2006 VLBI report - LBA Operations & eVLBI

LBA allocated time Disk-t ests Obs ervations Time lost due to weather Time lost due to other failures

19 days 56 hrs 346 hrs

14% 86% 4% 1.5%


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3) eVLBI Pr oject a) Fast networ k connecti ons The broadband "last-mile" fibre links to the telescopes were constructed in the period December 2005 to February 2006. The AARNet3 backbone was lit at the end of January 2006. The ATNF worked clos ely with AARNet to define, purc has e and install the required interfac es from the telescopes to the fibre links. The network became available for testing during the March 2006 LBA session. Many net work tests were performed and the highlights include: · Tests ac hiev ed net work speeds exceeding 900 Mbps between Marsfield and eac h of the ATNF antennas. Peaks of 940 Mbps were reac hed, close to the expected 950 Mbps maximum on the 1 Gbps fibre. · Data was written directly from the telescope to dis ks in Sydney. Speed was limited by the comput ers and disks and not by the net work · Network tests to UWA via Sydney and the CeNTI E fibres to WA achiev ed speeds > 700 Mbps · First fringes were obtained with the fringe-testing software running on the Cray XD1 in UWA. Thes e were for only 64 Mbps (1 channel of 16 MHz ) but the limits were on the hardware set up and disks and not on the net work. Further tests were performed in the May 2006 LBA session. The real-time fringe-testing system was s witched onto the fast links and was limited primarily by the slower links into Swinburne. The "last-mile" fibre connections were bought from AARNet and ownership is now fully by CSI RO and ANU (for Mopra). The construction costs were paid by CSIRO corporate in May 2006. Howev er, the AARNet3 1 Gbps links to the observ atories were turned off on 29 May!! This is due to legal issues conc erning the regional net work agreement bet ween AARNet and CSI RO. The issues involve indemnity and liability clauses and hav e been referred to the AARNet board for legal rev iew. b) Disk-based recor The new computers commissioned at all systems were us ed di ng and disk-bas ed VLBI recording system has been LBA sites and is working extremely well. The s ame for the connections to the fast net work.

The disk systems can now be routinely us ed at 256 Mbps at all LBA antennas and at 512 Mbps at the ATNF sites, using 2 DAS units. Most LBA observ ations in the May session were rec orded on disk. Tests have ac hiev ed 512 Mbps rates for a single DAS us ing new cables and connectors, whic h seem t o hav e solved the timing problems previously encount ered. This enables 512 Mbps operation at all LBA antennas and 1 Gbps operation at the ATNF antennas. The 1 Gbps operation was successfully tested between Parkes and the ATCA in March 2006. However, more testing will be perf ormed before these are made widely available for LBA observ ations. c) Softwar e correlator s Soft ware correlators have been developed by the Swinburne University of Tec hnology using their superc omputer cluster and a Cray computer at UWA.


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Such c orrelators will be the only VLBI correlators f or the disk-based system and for high data rat es, until the new CABB correlator at Narrabri comes online in about 3 years. The FX version of the Swinburne s oftware correlat or has been commissioned and it is now used for all correlation, inc luding real time fringe tests. This correlator performs very close to real time by utilising 30-40 superc omputer nodes. The next version of the FX correlat or, due in mid 2006, will include "streaming" inputs wit hout the need for disk buffering. This will enable real eVLBI for the first time in Australia and tests are planned. d) 5th e-VLBI wor kshop The 5th annual international eVLBI works hop will be in Haystack in 2006, where the 1st workshop was held in 2002. It will be held in the period 17-20 September 2006 and will include a large component of net work iss ues.

4) LBA evol uti on a) Transiti on to disk systems The av ailability of reliable disk-based rec ording systems and the soft ware correlators makes possible the transition of LBA operations from the aging S2 tape-bas ed system to the new disk-based system. This also offers signific ant upgrades to LBA c apabilities i.e. a x2-3 increas e in sensitivity and huge (unlimited?) increases in spectral line channels. As a first step, Swinburne and ATNF are negotiating an agreement for Swinburne to assume res ponsibility for all LBA c orrelation later in 2006. Swinburne will als o manage the transition from t apes to disks ov er approximately the next 12-18 months. Full disk operation will be ac hiev ed once enough disk capacity is acquired by the LBA partners. A LIEF propos al has been submitted to the ARC t o fund the necess ary data acquisition and extra nodes at Swinburne for LBA correlation. Operat or support of correlation on the old LBA c orrelat or will cease by the end of 2006. Under current plans the S2 tape-system should be dec ommissioned in 2007. b) Telescope support ATNF and Univ ersity of Tas mania hav e als o been negotiating on National Fac ility support of LBA operations at the Hobart and Ceduna observatories. ATNF has agreed to fund the initial request from UTas for the next financial year and review and plan for future support.