We announce the opportunity for coordinated, high angular resolution and high sensitivity GLOBAL VLBI observations in the 3mm band (near 86 GHz), complementing existing stand-alone VLBA observations at these frequencies. At present, the Global 3mm VLBI Array consists 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). With this VLBI-array, compact radio sources can be imaged with an angular resolution of down to 40 micro-arcseconds.
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 coordinated and scheduled in time blocks during dedicated observing sessions, performed twice per year. Interaction between P.I. and array schedulers guarantees optimum use of observing time. The dates for the spring and autumn sessions in 2006 are not yet fixed, but will be near to April and October 2006. The actual duration of each session will depend on proposal pressure.
The Global 3mm VLBI Array supports most of the standard observing modes used at the VLBA, and uses MK5 hard disk recording. For continuum observations the standard recording rate is 512 Mbit/s. For logistical reasons, the duty cycle (recording time/total time) of the observations is limited to 0.2-0.3 for 512 Mbit/s (VLBA requests changes of 8packs every 24 hrs).
Recording at 1024 Mb/s is also possible at the European stations (the VLBA formatters cannot yet reach this bit rate), but is available only on request and after special justification.
These new and higher recording rates now lead to an improvement in continuum detection sensitivity by a factor of 1.4 - 2. This became possible owing to the upgrade of the VLBA to Mark5 disk recording last year.
The correlation will be performed in absentia at the Bonn MK5 VLBI correlator 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 2006 session should be prepared in a similar fashion to ``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 VLBI Scheduler, 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. Whether a project is scheduled will depend upon the combination of both the European and VLBA review processes.
Global VLBI observations at 3mm are subject to some technical restrictions, which are summarized on the following web-page
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 (critical limit about 5 Megabytes), 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.