IRAM has bought and installed two Mark5A terminals for its VLBI systems on Pico Veleta and Plateau de Bure in early 2004, which allow higher data rates and thus larger observing bandwidths than the previous Mark4 recorders. Plateau de Bure also received a new FS9 computer; the old one is kept operational for redundancy.
In April 2004 Pico Veleta successfully participated in the Global session, but Plateau de Bure encountered a problem with its maser 10 hours before the session started, resulting in a 100% loss of the station (the weather was quite bad, too). It is now sure that the maser can be repaired but that it will not be available for the October 2004 session. Fortunately we will have a replacement before the end of the summer: the geodetic station in Wettzell, Germany, has kindly agreed to lend IRAM a maser until May 2005. Chances are therefore good that both IRAM instruments will be able to participate in the next Global sessions in October 2004 and April 2005.
We announce the opportunity for coordinated, high angular resolution and high sensitivity GLOBAL VLBI observations in the 3mm band (85 - 95 GHz), complementing existing stand-alone VLBA observations at these frequencies. The Global 3mm VLBI Array consists at present of 8 VLBA antennas equipped with 3mm receivers, plus the IRAM 30-m telescope on Pico Veleta (Spain), the IRAM phased 6-element interferometer on Plateau de Bure (France), the 20-m radio telescope in Onsala (Sweden) the 14-m telescope in Metsähovi (Finland) and the MPIfR 100-m radio telescope in Effelsberg (Germany).
The Global 3mm VLBI Array offers 3 to 4 times more sensitivity than the stand-alone VLBA. Observations with the Global 3mm VLBI array will be scheduled in time blocks in special observing sessions, performed twice per year. The next two sessions are planned for October 8-13, 2004 and April 16-21, 2005. The observing date in April is still tentative. As in the past, the actual duration of each session will depend on proposal pressure.
The Global 3mm VLBI Array basically supports the same observing modes as the VLBA. For standard continuum observations the VLBI recording will be done at 256 Mbit/s (corresponding to a bandwith of 128 MHz). Depending on resources, a limited amount of observing time may be used to record with 512 Mbit/s, but no more than two tapes in 24 hrs. Proposers who wish to observe at 512 Mbit/s should explicitly justify this in their proposal. Correlation will be performed in absentia at the MPIfR MK4 correlator in Bonn unless some technical reason for using another correlator is given in the proposal. The P.I. will receive the correlated data in uv-fits format.
Proposals for the April 2005 session should be prepared in a similar fashion as ``normal cm-VLBI proposals'', using the standard VLBI cover sheet and instructions available on the web under URL http://www.nrao.edu/administration/directors_office/vlba-gvlbi.shtml and should be submitted electronically as e-mail before
to the following two addresses (in copy):
Proposals will be reviewed by NRAO and the participating European Observatories.
The European Schedule Coordinator, Dr. R. Porcas (MPIfR), will forward proposal copies to the participating European Institutes and ensure the scientific evaluation of the proposals by the respective local committees. Finally, the referee ratings of these observatories and the NRAO will be combined.
Global VLBI observations at 3mm are subject to some technical restrictions, which are summarized on the following web-page (http://www.mpifr-bonn.mpg.de/div/vlbi/globalmm/index.html).
VLBI observations allow unique insights in the astrophysics of compact and bright sources. Please prepare your proposals carefully, as they are equivalent to asking simultaneously for observing time on a large number of telescopes. Avoid last minute submissions: the e-mail submission may bounce large e-mails, returning them with details on how to submit via anonymous FTP. See http://www.nrao.edu/administration/directors_office/vlba-gvlbi.shtml for more information.