1. VLBI/eVLBI with the 305-m Arecibo Radio Telescope Chris Salter Tapasi Ghosh Emmanuel Momjian Arun Venkataraman Jon Hagen

2. Timeline The post-upgrade 305 m Arecibo radio telescope became a part of the VLBI network in late 1990s for the HALCA mission of the Japanese VSOP project (S2 recorder). In 2001, Arecibo acquired its hybrid tape-based VLBA-Mark IV (VLBA4) recording system. In 2004, the Observatory procured its Mark 5A disk-based recording system, enabling the largest telescope in the world to become electronically connected to other radio telescopes in the world in real time via eVLBI observations.

3. First-ever Transatlantic eVLBI The first eVLBI test observations took place on Sept. 10, 2004. The source, 0528+134, was observed at 1.6 GHz using an array consisting of Arecibo, Cambridge (UK), Torun (Poland) and Westerbork (Netherlands). The observations resulted in the FIRST transatlantic eVLBI image. Arecibo- Torun is believed to be the LONGEST real-time interferometer baseline yet created. (Top) The 1.6 GHz continuum image of 0528+134 at 80 mas resolution. (Below) Visibility amplitude and phase plots between Arecibo and other EVN stations.

4. Science Demo: 3C 166 The first scientific eVLBI observations took place on September 22, 2004. Arecibo, Torun, Westerbork, and Onsala (Sweden) participated. The ULIRG IRAS 06487+2208 and radio galaxy, 3C166, were observed. 1.4 GHz continuum image of 3C166 at 32 x 19 mas resolution. The peak flux density is 318 mJy beam -1. The contour levels are at 4, 8, 16, 32, 64, 128 times 1  (1.8 mJy beam -1 ).

5. Data Path to JIVE  PRISANET (PR) of the Arecibo Obs./UPR.  AMPATH (US) of Florida Intl. Univ.  Abilene (US) of Internet 2.  SURFnet (NL) of SURFnet BV. Data rate: 32 Mbps sustained 80 Mbps. DAR/Formatter MK5 JIVE in2net

6. eVLBI Advantages No need for disks/tapes. No need for disks/tapes. Speed at which results are obtained. Speed at which results are obtained. Target of Opportunity. Target of Opportunity. Real-time monitor of Station reliability. Real-time monitor of Station reliability. Reduced manpower at VLBI station. Reduced manpower at VLBI station. No longer observing blind. No longer observing blind.Disadvantages Fear of single point failure. Fear of single point failure. No multi-pass correlation. No multi-pass correlation. Loss of low bandwidth stations. Loss of low bandwidth stations. Presently lower max bit rate than disks. Presently lower max bit rate than disks. Capital and recurring costs of links. Capital and recurring costs of links.

7. Current & Near Future Activities From Sept. 2004, disk-based Mark-5 operations with EVN. From Sept. 2004, disk-based Mark-5 operations with EVN. From Dec. 2004, regular observing as part of the High Sensitivity Array (HSA; VLBA,Y27, GBT, EB, AR). From Dec. 2004, regular observing as part of the High Sensitivity Array (HSA; VLBA,Y27, GBT, EB, AR). February 27, 2005: First scientific 1 Gbps disk recording was made. February 27, 2005: First scientific 1 Gbps disk recording was made. March 11, 2005: Continuum Science Demo. Up to 128 Mbps for 4 hours total. March 11, 2005: Continuum Science Demo. Up to 128 Mbps for 4 hours total. Mid Summer 2005: Ultra wide-band VLBI test (Haystack initiative) with 2 Gbps disk recording. Mid Summer 2005: Ultra wide-band VLBI test (Haystack initiative) with 2 Gbps disk recording.