1. mmVLBI in the Future: technical/experimental Shep Doeleman Haystack Observatory

2. In Defense of Theory Do I contradict myself? Very well then I contradict myself, (I am large, I contain multitudes.) --Walt Whitman, "Song of Myself"

3. High Frequency VLBI Challenges Sensitivity: limited by atmospheric coherence, telescope apertures, bandwidth, weather (opacity and coherence). –Past observations limited to brightest sources. Baseline coverage: limited by relatively small number of high demand sub/mm telescopes. LO quality: phase noise in electronics increases – loss of fringe amplitude. –First VLBI at new mm sites requires effort.

4. Challenges cont’d Scheduling: mm/submm telescopes difficult to schedule. Array phasing: all antennas must be phased prior to summing (you only get one chance). Hydrogen masers: if atmosphere is good, maser should not limit coherence time. Amplitude calibration is difficult: array phasing, pointing, atmosphere, gain curves. BBCs have limited Bandwidth Major improvements can be expected in some of these areas.

5. Sensitivity: a solution. Old conventional wisdom: collecting area. New technical developments – new wisdom –1983 VLBI BW: 224Mb/s, –2004 VLBA BW: 512Mb/s. –New disk based VLBI recording systems will allow multi Gb/s data rates

6. Mark 5A VLBI Data System Mk5 cost ~ $15K 700 GB disks expected ~2005 – 24 hours @ 1 Gbps unattended (comparable to ~19 VLBA tapes)

7. Sensitivity: a solution. Old conventional wisdom: collecting area. New technical developments – new wisdom –1983 VLBI BW: 224Mb/s, –2004 VLBA BW: 512Mb/s. –New disk based VLBI recording systems will allow multi Gb/s data rates. –Leverages COTS technology and industry demand for affordable, high capacity, high speed hard disks. –Units can be used in parallel for N Gb/s.

8. Tape vs. Disc Price Comparison

9. mmVLBI at Haystack 2001-present: focus on 1-2mm VLBI 2002: Carried out successful 129, 147GHZ VLBI on Pico Veleta, KittPeak12m, SMTO triangle: –High resolution: Pico-SMTO fringes – 49  as –SiO Masers –Collaborators: MPIfR, IRAM, Onsala, Metsahovi, Arizona Radio Observatory

10. mmVLBI In the News

11. v=1 J=3-2 SiO Masers in VY CMa 30 AU First 129GHz VLBI image using all phase and amp information. Relative astrometry small fraction of beam.

12. mmVLBI at Haystack 2001-present: focus on 1-2mm VLBI 2002: Carried out successful 129, 147GHZ VLBI on Pico Veleta, KittPeak12m, SMTO triangle: –High resolution: Pico-SMTO fringes – 49  as –SiO Masers 2003: Carried out 129, 230GHz VLBI using Pico, KittPeak, SMTO, Plateau de Bure –Detected Pico-SMTO 1.3mm fringes – 34  as on 3C279 –World Record: equivalent to 5 R SCH of SgrA* MBH –Used new generation of VLBI recorders. Very promising, but future depends on funding.

13. Evolution of 3mm Capability AntennaSEFD (Jy) VLBA5170 PicoVeleta1700 P. de Bure1700 Onsala4000 Effelsberg2000 Present: 256Mb/s AntennaSEFD (Jy) GBT500 Apex (Chile)5000 CARMA1700 LMT350 Nobeyama3000 3-5 years: 1Gb/s AntennaSEFD (Jy) ALMA60 5-10yrs: 10Gb/s VLBA-VLBA = 0.8Jy PicoV-PdeB = 0.25Jy PicoV-PdeB = 0.13Jy* PicoV-VLBA = 0.5Jy VLBA-VLBA = 0.4Jy GBT-LMT = 0.032Jy GBT-LMT = 0.016Jy* LMT-VLBA = 0.1Jy VLBA-VLBA = 0.13Jy ALMA-LMT = 0.004Jy ALMA-VLBA = 0.014Jy Resolution (8000km)=90  as Tcoh = 20 seconds Higher recording rates.

14. Evolution of 1mm Capability AntennaSEFD (Jy) KittPeak22000 PicoVeleta2500 P. de Bure2500 SMT15000 Present: 0.5Gb/s AntennaSEFD (Jy) JCMT7800 APEX-Chile5500 CARMA2500 LMT500 SMA2500 CSO15000 3-5 years: 4Gb/s AntennaSEFD (Jy) ALMA100 5-10yrs: 10Gb/s PicoV-PdeB = 0.4Jy PicoV-KittPeak = 1.15Jy LMT-CARMA = 0.06Jy LMT-SMT= 0.15Jy ALMA-LMT = 0.008Jy ALMA-SMT = 0.042Jy Resolution (8000km)=34  as Tcoh = 10 seconds

15. UltraVLBI Proposal Submitted to ATI program at NSF Outfit largest cm antennas (Effelsberg, Arecibo, GBT, WSRT, Jodrell bank) with 4Gb/s recording systems: <1  Jy/beam rms. Outfit best mm sites with 4Gb/s systems: JCMT, SMTO (CARMA, LMT, SMA, ALMA, APEX) Target science requiring sensitivity: SNR in Galactic mergers, GRBs, Grav. Lenses, Stellar VLBI, SgrA*!! Waiting to hear …

16. 230GHz VLBI Observations Proposed VLBI on JCMT-HHT baseline. Just a detection will provide a firm upper size limit.

17. Next Generation VLBI System Multiple Digital BBC units (500MHz each). –Cost: 20K each. Multiple MK5b units (1Gb/s each). –Cost: 16K each. H-maser with  y (10sec)<=3e-14. –Cost: 175K. Rack with power supplies, backplane, GPS clock, –Cost: 20K Total: $270K/new station, much less if maser is already available.

18. Summary Over next decade: BW x40, Element area x25, means capable 230GHz imaging arrays. Phase stability of mm/submm arrays is very important: CARMA, ALMA, PdeBure. Creating low phase noise LO systems for submm VLBI is necessary. VLBI arrays up to 345 and 450GHz are possible. ‘Widebanding’ IFs and receivers will be a requirement. Scheduling: need turn-key operation from single dish to VLBI. Current proposed work: 4Gb/s VLBI on SgrA* in 3 years.

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