TOG Meeting Summary IRA Bologna 27 Sep 2002 Fairly extensive abstracts were submitted to EVNtech before the meeting. The summary given below focuses on items that arose during the meeting and were not covered in the abstracts themselves. A concatenated list of abstracts can be found at: www.evlbi.org/tog/tog_bol_2002_abs.txt On-going Action Items: ------------------------- 6 & 18cm dual poln receivers at DSN antennas - PETER POON reported that a request for these facilities had been submitted and "queued". ACTION ITEM: STATIONS who wish to take advantage of the recorder tests (see recent EVNtech message from van Langevelde) to send test tapes to JIVE asap. TR BBC problems continue, esp with 512Mbps. ACTION ITEM: CONWAY to investigate whether spare BBCs at SEST could be procured. Schedule checking: VENTURI reported that she has in the past checked the Block Schedule. ACTION ITEM: GARRETT to investigate whether individual schedules can be checked by JIVE Support Scientists. ACTION ITEM: REYNOLDS to check whether TSYS data is now available from DSN antennas and report back to POON and GARRETT Barrell rolling - several EVN telescopes now using this mode for geodesy, not yet supported at JIVE. ACTION ITEM: BURGESS to repost information about availability of MkIV decoders (done) BURGESS to revise list of spares, in particular what should now be held locally/centrally as disk-based systems replace tape. ACTION ITEM: GARRETT to request POLATIDIS to make a new call for station input w.r.t. EVN STATUS sheet (several more antennas now with freq switching) MkIV Spare formatter - discussion to be led by VOLVACH, Alef, Himwich & Garrett w.r.t. moving spare formatter to Simeiz. Can the formatter be shipped on a temporary basis with the understanding and guarantee that it must be returned *immediately* by express shipment (time scale of a few days) should the EVN require it. ACTION ITEM: HIMWICH/VAN LANGEVELDE to close the loop w.r.t. final continuous post-pass at the end of expts, plus 2 min read-back tests. Summary of TOG activities: --------------------------- See concatenated reports at www.evlbi.org/tog/tog_bol_2002_abs.txt Tape supply limits use of 2-head 512 Mbit/sec modes by user expts. No user expts have yet been scheduled. This is very disappointing, especially given the efforts made by all to install and test two head recording, correlation and analysis. Conway noted that 512 requires some justification - instantaneous sensitivity (e.g. high frequency obs where the coherence timescale is short). It is noted that short expts (~ few hours) might make good use of 512mbps modes (more efficient use of tape). EVN Performance and Reliability -------------------------------- See concatenated report at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt Conway pointed out that correction factors (gains) listed in table 1 had to be squared in order to see estimate the antenna amplitude calibration error. Gains of 0.9 then corresponded to an error in the antenna calibration of ~ 20%. van Langevelde noted that the first few passes on a tape gave poorer playback than later passes. He encouraged all stations to pre-pass tapes before observing. van Langevelde also requested that stations provide feedback to EVNtech when major failures occurred. Garrett noted that such feedback while it was painful, often proved a useful way of forewarning others of possible pitfalls. van Langevelde noted that sometimes errors that were not known at the time of the expt or shortly thereafter (i.e. did not appear in the logs or Expt feedback facility) were sometimes reported to individuals at JIVE. van Langevelde requested that reports should be sent to jops@jive.nl so everyone at the correlator was aware of what was going on. ACTION ITEM: All stations to ensure feedback is provided via the logs, the EVN expt feedback facility and jops@jive.nl Amplitude Calibration ----------------------- Conway noted the various FS developments that were now underway to ensure better EVN calibration: the FS logs are now formatted in a standard way - this will make it much easier to delog FS logs and produce ANTAB TSYS files. This standardisation is part of 9.5.12. In the new system calibration will become self-contained within the FS (DPFU, gain curves, TCAL tables are all included in the system - rather than being spread across several different sources). ACTION ITEM: ALL EVN STATIONS to upgrade to the latest version of the FS (9.5.12) asap. The new FS calibration package will permit the TCal to be measured as a function of frequency. It also unifies the abs. flux values used for calibrators. Continuous TSYS seems to work well for MkIV racks (Reynolds). Since the VLBA BBCs have AGC the same technique of monitoring TPI cannot be used. An attempt has been made to monitor the changing attenuation in the BBCs and use this to infer TPI - so far this has failed. The attenuation does not seem to be changing in some cases. Perhaps this can also explain the poor sampling statistics of some stations. ACTION ITEM: BURGESS to check whether VLBA racks are doing the right thing w.r.t. changing attenuation by inserting test signals and reporting back to EVNtech. ACTION ITEM: GARRETT to contact EVN scheduler and CBD to discuss short calibration expts to be scheduled and included within the block schedule - just like normal user expts. Logs etc will be deposited but no tape/disk will spin. Format of the expt name will be CL02L1 (i.e. CL = amp calibration expt; 02 = year; L1 = L-band 1st amp cal expt of that year). ACTION ITEM: GUNN to act as PI for these calibration expts. Several other action items w.r.t. calibration were later refined at the Calibration workshop. See list of action items distributed by Conway - www.evlbi.org/tog/togmins/cal_wshop_actions.txt N.B. The Calibration Workshop was sponsored by RADIONET - at least one representative from each of the EVN institutes (those directly associated with the RADIONET ICN contract) can claim their travel expenses from this source (see your local director). FS developments ---------------- See report at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt ACTION ITEM: REYNOLDS & HIMWICH to investigate the production of UVFLG files from FLAGR data written to logs. ACTION ITEM: ALL STATIONS to ensure that the FS FLAGR can run at their telescope. ACTION ITEM: REYNOLDS to compare FLAGR data with correlated (drop-out) data in case there are latencies within antenna control systems. As always, VLBI friends were asked to communicate all feedback w.r.t the FS to Ed Himwich: weh@ivscc.gsfc.nasa.gov Sched ------ See report at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt S/X schedules - Dave Graham has an adhoc solution that works; we should use this until something better turns-up. For more details consult: www.mpifr-bonn.mpg.de/xastrogeo.html van Langevelde is no longer able to support Sched. It's important that a replacement is found soon as Walker cannot support EVN related enhancements. With disk-based PC systems just around the corner support for Sched must be sought immediately. ACTION ITEM: GARRETT to raise the TOGs concerns w.r.t. manpower for SCHED at the next CBD meeting. Global VLBI ------------ * VLBA - See report at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt The VLBA is no longer the new kid on the block - many other project competing for man-power and skills (ALMA, EVLA, GBT). The VLBA would like to see *one* PC disk-based system around the world - but no decision yet. Two Mk5 systems are undergoing tests now; first fringes are expected soon. * LBA LBA is looking to replace S2 with a disk-based PC system. Apparently M. Bailes at Swinbourne has a disk-based system (used for Pulsars) that might be viable. Software correlators are also being investigated by the same group. Digital BBCs have been used for sometime at the LBA. ACTION ITEM: TUCCARI to contact LBA w.r.t. their experience with Digital Filters. Logistics ---------- No problems reported. ACTION ITEM: ALL STATIONS to continue to use the BOLOGNA RULES - see www.evlbi.org/tog/bol_rules/bol_rules.txt Disk-based recording systems ----------------------------- See reports at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt and www.mpifr-bonn.mpg.de/EVN/m5.html By far the dominating issue of the meeting was the topic of disk-based recording systems. The features of both PC-EVN (Parsley) and Mk5 (Smythe) were well presented and widely discussed. Each system has its merits. Mk5 is now deployed by the geodetic community, including several EVN stations. Alef reported on the successful installation and operation of Mk5 systems at Effelsberg and at the Bonn correlator. The Bonn experience is a very positive one - the system works robustly (disk changes are easy, data integrity is secured and full support is available via the FS). Parsley reported that first fringes have been obtained with the PC-EVN system. The PC-EVN system is not yet controlled by the FS but this should be possible in future versions of the system. PC-EVN would very likely use the disk pack system now employed by the current generation of Mk5 systems. During and after the TOG, several VLBI friends expressed their desire to begin using disk-based systems asap. The general feeling of the TOG is that we would like to see all EVN telescopes and the EVN correlator at JIVE with Mk5 capability as soon as possible. An excellent case for continuing PC-EVN developments can also be made (especially in terms of the very impressive and successful fibre-based fringe tests presented by Parsley). It's essential both systems use the same standard disk packs. The GVWG is expected to report on compatibility issues for disk based system at the KVN meeting in Korea (early November). In the meantime the TOG will set up a small group of people to investigate the consequences of moving to disk-based systems immediately. There are many implications to consider, for the EVN in particular. ACTION ITEM: GARRETT to set-up a small group to discuss the wide-ranging implications of employing disk-based recording systems within the EVN. EVN Fibre developments ----------------------- www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt Parsley reported on the fibre tests conducted only a few days before the TOG meeting. VLBI data recorded by PC-EVN had been taken to the Manchester computer centre and then transferred via a shared network connection to JIVE. Data rates of 40 Mbit/sec were achieved with ftp and up to 700 Mbit/sec with UDP. Fringes (WB-JB) were found at the JIVE correlator. The full process (including web-cam images from JIVE) was presented "live" at the iGRID meeting in Amsterdam. There is *significant* interest from the National Research Networks and GEANT to support the direct connection of several EVN telescopes to JIVE within the year. Further tests using the new fibre link to JIVE are planned over the next few months. Rapid developments are taking place in this area, it seems that now is exactly the right time for the EVN to exploit the capacity that is now available on these networks. Hardware problems ------------------- Not much to report - that is not already known. The desire to move the recorders out of the door asap was a recurrent theme. There are significant gains to be achieved all round, but in particular those cases where maintenance is high. Spare parts ------------ www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt Most of the money for spare parts was now available. ACTION ITEM: Burgess to begin purchasing various components. It was agreed that it was now silly for stations to buy spare recorder heads. A common pool should be established. MPIfR and JIVE volunteered to provide heads in emergency situations (stations would buy the heads of course at the standard cost). JBO may also have a few extra heads. ACTION ITEM: STATIONS to contact MPIfR and JIVE for replacement heads if they have no spares locally. ACTION ITEM: BURGESS to update http://newton.jb.man.ac.uk/obsol.htm based on comments from other TOG members. EVN and the EC FP6 programme ----------------------------- Several Joint Research Activities have been proposed that related to the EVN. These include: - EVN software: incl. FS, Sched devs, EVN correlator, AVO, archiving. - RFI mitigation - Replacement of analogue BBCs etc with digital filters - eVLBI: support for testing/development of fibre links, real-time vlbi - mm & cm receiver development - Transnational access: EVN plus others. Roy suggested JRA might include activities related to water-vapour radiometer measurements (to correct phase) and multi-freq phase-referencing techniques. ACTION: ROY to communicate these suggestions to DIAMOND/SCHILIZZI/ZENSUS Future VLBI Technological Devs ------------------------------- Most things had been covered in other parts of the agenda. We seem to be entering a period where the emergence of wide-bandwidth digital front ends (e.g. e-MERLIN) need to be considered. EVN Telescope/Correlator reports --------------------------------- See reports at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt q Yebes 40-m: excellent progress was reported by Vicente. It was noted that there are no plans to have L-band, C-band or 6-6.7 GHz capability - currently the EVNs main observing frequencies. e-MERLIN: significant disruption of EVN activities was likely during the switch over from MERLIN to e-MERLIN ops. Burgess is active in trying to ensure this will be kept to a minimum for the home telescopes that are vital for the EVN (Lovell, Mk2). Effelsberg: there are plans to replace the sub-reflector, subject to funding. Hopefully disruption will be minimised. EVN archive ------------ See reports at www.evlbi.org/tog/togmins/tog_bol_2002_abs.txt