VLBI Plans at Arecibo in the Near Term

Dear Colin,

Greetings from Puerto Rico.

Murray Lewis has asked me to contact you concerning VLBI developments
at Arecibo in preparation for the "Future of Arecibo" meeting.

Equipment wise, what we presently have is a VLBA4 data acquisition
rack, a Mark5A recorder (the VLBA4 tape recorder is there still but has
not been in use for a while now), a Symmetricom (late Sigma-Tau)
hydrogen maser, and the big dish with its receivers.  These receivers
are capable of providing up to 1-GHz bandwidth per polarization  in the
COntrol Room at a given time and covering various frequency ranges from
327 MHz to 10 GHz; (the 1-GHz bandwidth limitation is imposed by our
current If/LO system, although a number of the receivers cover ~2 GHz
of bandwidth). The path to the VLBA4 rack further limits this to
500-MHz bandwidth per polarization. We have been co-observing with the
EVN, Global, and HSA networks. Earlier, we participated in HALCA
observations, and expect to do the same at X-band with VSOP2.

On the e-VLBI front, we had a number of successful runs with JIVE in
2005 with data rates of 32 Mbps, and once even at 64 Mbps.  This got us
included into the JIVE EXPReS project, albeit with only a relatively
small amount of monetary help from this. As you would know, the goal of
EXPReS is to achieve 1-Gbps eVLBI within three years.  (Perhaps I
should note that Arecibo is an associate member of EVN.) With a lot of
innovative collaborations, Arun (our computer Dept.  Head) has worked
out a way to achieve 512-Mbps connectivity to the Florida International
Univ.'s gateway to Internet2.  We hope that this will be available from
this fall when the telescope emerges from the present painting of its
suspended platform.  We are now looking into the possibilities of
finding additional funds to get towards 10-Gbps connectivity to the
main land within the next three years. In addition to enhancing our
eVLBI capability, this will also make the transfer of all ALFA survey
data to the processing centers around  the world much easier.

In collaboration with the University of Puerto Rico (Humacao campus) we
are also planning to look for funds to add an additional small
(18-meter diameter) dish to be situated at the Observatory. This will
improve the efficiency our phase-referenced VLBI observations by
eliminating much of the need for the large telescope to drive to the
reference source at its relatively slow rate. In addition, the small
antenna could itself be used for geodetic VLBI (particularly, given the
improved eVLBI connectivity), for the monitoring of transient/variable
sources, some planetary radar work, and for student teaching in
collaboration with the UPR centers.

We are keeping our eyes on the DBE developments. We would like to
record the full available 1-GHz bandwidth that arrives at our DAR (2 x
500-MHz bandwidth) as soon as possible. This requires a 4-Gbps system,
such as that which Haystack are intending to bring here for a
pathfinding experiment with the GBT later this year. Such a system
would facilitate very high sensitivity-observations (increasing the
brightness temperature sensitivity for objects that could then be
detected at mas resolutions.)

Given the impending budget cuts here after the Senior Review, we need
to develop a realistic plan for now, keeping within the present budget.
We can then see for what we need to look around for additional funds.
(Two examples where we clearly need extra funds, I have mentioned
above).  For some projects, collaboration is the only way to go.

Here, I have just jotted down the current/near-term  situation in
respect of the VLBI-related equipment at Arecibo. The people most
involved in aspects of VLBI at Arecibo are Chris Salter, Emmanuel
Momjian, Arun Venkataraman and myself. If  you have any questions
regarding any of the above points, please don't hesitate to write back
and ask.  I am looking forward to the discussions of scientific
questions that can be addressed by VLBI observations involving Arecibo
at the Futures Workshop.

With Regards,

Tapasi