NAIC presently commits Arecibo to supporting VLBI observing up to a
maximum of 4% of the 305-m's observing time. Two hydrogen maser
frequency standards are available for VLBI recoding at Arecibo. The
older of the tow is a Model NR16, originally built by APL. This was
supplied on loan by the Frequency Standards Lab. of NASA Jet Propulsion
Laboratory for a number of years, and ownership has since been
transferred to NAIC. The newer unit is a model from Symmetricon Inc.
(ex-Datum/Sigma-Tau), Model No. MHM2010. For information on this unit
see http://www.symmttm.com/products_pfr_MHM2010.asp
As well as being used as the primary Arecibo frequency standard, the
newer maser is serving as the master clock of the Observatory.
Arecibo is equipped with a a VLBA4 recording system, compatible
with the VLBA, EVN and Global networks, and the 305-m telescope is
now available for scheduling in conjunction with all 3 networks. Any
proposer wishing to include the 305-m telecope in their VLBI
observations should submit their proposals for the VLBA, the EVN or
Global networks as usual, rather than to Arecibo. In all proposals,
special justification for the use of Arecibo should be included.
(Observations with ad-hoc arrays will also be considered, but in this
case proposals should be submitted to Arecibo as specified at
http://www.naic.edu/~astro/proposals/proposal.htm.
It is the
proposers' responsibility to ensure that telescope time be granted by
the other observing facilities involved.)
In the summer of 2004, Arecibo took delivery of a Mark-5A disk-based VLBI recording system. This uses the VLBA4 Data-Aquisition Rack, together with the Mark-5A unit. The Mark-5A system allows recoding at a 1 GBit/s rate, compared to a 500 MBit/s rate with the LVBA4. In addition to replacing the heavy, expensive magnetic tapes with disk packs, the Mark-5A system allows Arecibo to participate in real-time e-VLBI. Amounts of data can also be transferred off-line to the JIVE correlator by ftp, permitting (for example) establishment of fringes pre-observation.