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\clearpage

\title{JOHN BALDWIN DAY - SPECTRAL LINE IMAGING}
\author{Melvyn Wright}
\begin{document}


\maketitle
\scalefont{1.5}

\clearpage

\section*{IN MEMORY OF JOHN BALDWIN}
%\begin{itemize}

John B was my PhD advisor. I was  the first research student on the new Half Mile Telescope.
My job was commissioning both spectral line and polarization aperture synthesis.
This was a great privilage  although I was too young  to realize it at the time.
The HMT comprised of two 30-foot  antennas and a novel, analog, time domain XF correlator
-- which is a fancy name for a 1 km coax cable tapped at 11m  intervals to give a series
of time delayed  signals from the two antennas. The Fourier transform of
the sampled cross correlations  gives the  spectrum of the radio signal.
Something dreamed up by John B.  Chris Fields designed and built this spectrometer for his PhD.
I tested it using the Wurtzburg antennas at Lordsbridge.
It did not work very well.  It could detect only the brightest radio sources like Cas A and the Sun.
  
I wrote a spoof paper on setting astronomically significant limits from non-detections
with an instrument that could not detect known radio sources.  John  took it in his stride,
but he was happier with more positive results.  John had a terrific sense of humor.

There were several well defended opinions why the spectrometer did not work as expected.
These took place  between the benches in the electronics lab in the Old Cavendish. 
 I wrote in my thesis: 
 " I am indebted to Professor  Ryle for a discussion about the spectrometer,
which suggested that the fault  was with the low frequency ( 0-5MHz) part of the spectrometer,
and to an argument between Dr D.M.A. Wilson and Dr P. F. Scott which clarified my ideas on detectors." 

The spectrometer was only looking at the peak signal power and not integrating over the sampling interval.  The problem was solved  with a circuit re-design  and 
several happy afternoons with a soldering iron sitting in the sun outside the lab at Lordsbridge
re-building the 71 amplifiers attached to the delay cable.

The Half Mile Telescope made the first spectral line aperture synthesis images.  The
1 arcmin resolution in a 96 arcmin field of view 
and 39 km/s resolution of the spectrometer were well matched  for observing HI in
nearby spiral galaxies.

Wikipedia:  The Half Mile Telescope ... 

"Used for Hydrogen Line studies of nearby galaxies and produced the first good radio maps of hydrogen distribution (as a function of its velocity), for M33 and M31 (also produced nearly 20 PhDs and 50 published papers)."

I observed M33  in 1969, Darrel Emerson observed M31 in 1970.
The HI  observations of M33 took  from July to October,  in order to accumulate aperture synthesis data
at 60 spacings from 40 to 1200 feet.
Each day I traveled by scooter to Lordsbridge to set up the observations for the night
with stop at the pub;  4 min earlier each day.   Eventually I had to skip the visit to the pub en route.

John B,   with John Shakeshaft, John Jennings, Peter Warner and Donald Wilson also pioneered  polarization imaging  with the Half Mile Telescope.  It was a wonderfully creative group
of people to work with. These were the first polarization aperture 
synthesis data, so there were a few details to be worked out.  One of which was calibration
of the relative gains of X and  Y polarizations.  This was a problem until John said why don't
we just put a calibration dipole in each antenna at 45 degrees to the X and Y feeds and measure
the XY gains. So we did. It worked, and using a polarized source has become a standard calibration  for polarization imaging.

John B was a can-do person. His enthusiasm was contagious.  Research  with John was fun.
He brought out the best in his students.

I remember field days with all hands at Lordsbrdge carrying cables to reconfigure the Hewish array
with John B as cheer leader.


%, but saw a cloud pass across his face and realized  that it was not so cool to poke fun at serious  astronomers.

John B pursued both spectral line and polarization aperture synthesis imaging with the Half Mile Telescope. After M33 and M31, polarization observations continued with IC443, imaged by  Ian Hill.
% http://adsabs.harvard.edu/full/1972MNRAS.157..419H. 
 %Ian was contemporary with Darrel.
 
Two more antennas were added in 1972, and several other galaxies were imaged in HI.

Winter, A.  1975, A study of the neutral hydrogen near the interacting galaxies NGC 4631 and NGC 4656

%Geoff Cottrell  imaged  HI in NGC3077  and HoII, in 1976

Cottrell, G. A.	1976  An aperture synthesis study of the irregular galaxy Holmberg II.

Cottrell, G. A.	1976 An aperture synthesis study of H I in the irregular II galaxy NGC 3077.

Cottrell, G. A.    1977. 21-cm observations of the interacting galaxies M81 and M82

Allsopp, N. J.	1978-1979
HI in the  dwarf irregular galaxy Leo A,  peculiar early-type galaxy NGC 3718, NGC 1023 and IC 239,
CVn I group. I - NGC 4136, 4144, 4190, IC 4182 and DDO 133.
%- see http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1976MNRAS.174..455C&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES

There were also HI observations of M101 and of M51
%, but I don't remember now who was doing those.

Keith Newton repeated the M33  HI  observations with twice the resolution.

 Steve Unwin repeated the M31  HI  observations with twice the resolution.
  % Keith Newton overlapped with me, and  helped me finish off some of the M31 writeups.

% Jim Piggins was contemporary with me, and built the first digital spectrometer.  I don't remember however what observations he made with it.
 
After the Half Mile Telescope, all aperture synthesis telescopes  were spectral line instruments. 
 
 With the discovery of molecular line emission
 at  millimeter wavelengths, spectral line observations became an essential tool
 in understanding the structure and evolution of stars and galaxies, and  gave us a 
 measure of the gas reservoirs  in  star-burst galaxies at high redshift.
 
 

 Focusing on some telescopes I have helped to develop and use:
 
  Jack Welch and Charles Townes  discovery of interstellar H2O and NH3 at Hat Creek
 opened up molecular line spectroscopy.

 Richard Hills and Jack Welch built  a 2-element interferometer at Hat Creek
 which showed that  H2O masers were closely associated with star formation.
 The Hat Creek interferometer expanded into the 10-antenna BIMA 
 millimeter wavelength aperture synthesis array which
 mapped comets, star formation regions,  stellar envelopes, and galaxies in
 molecular tracers such as CO, 13CO, HCN, HCO+, CH3OH, CH3CN........
 Interstellar chemistry became an astronomical discipline and  used as a diagnostic tool for
 the evolution of star forming molecular clouds.
 
 We build  spectral line correlators capable of mapping dozens of spectral
 lines simultaneously in multiple spectral windows spanning 10's of GHz.
 
Thus we can trace John's influence to the current telescope arrays at CARMA,
 SMA, IRAM, and the future ALMA.
 
John's legacy and work continues through his students and their students.
John's hands-on approach has continued in the  summer schools that
I have organized and taught  at Hat Creek and CARMA for
the last 25 years. This school has trained students from all over the world.  
Many of these students are
now the interferometry experts at major universities and observatories.
 
 John B was a mentor, a colleague and a friend. I'll miss him.
 Thank you John, for the inspiration of those early days.

\begin{figure*}[t]
\includegraphics[scale=0.8]{M33-Newton.pdf}
\caption{ M33 mapped in HI line emission with Half Mile Telescope. K. Newton, 1980}
\end{figure*}


\begin{figure*}[t]
\includegraphics[scale=1.2]{M33_velocity.pdf}
\caption{\small
   \setlength{\baselineskip}{1.5\baselineskip}
   M33 velocity field mapped in HI line emission with Half Mile Telescope}
\vskip -0.2in
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=0.99]{M81-M82-Cottrell.pdf}
\caption{ M81 and M82 mapped in HI line emission with Half Mile Telescope. G. Cottrell, 1977}
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=1.2]{ATA_WideField.jpg}
\caption{Allen Telescope Array 2000-2011.
42 antennas,  with 4 simultaneous RF bands in the range 0.7 to 11 GHz.
4  100 MHz bandwidth, 1000 channel correlators,  3 beamformers.
Used for radio surveys,  HI in spiral galaxies, radio transient surveys, SETI.}
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=0.8]{m31HI.pdf}
\caption{M31 HI distribution imaged with the Allen Telescope Array.
7-pointing mosaic with 8 hours per pointing. Garrett Keating, UCB.}
\end{figure*}


\begin{figure*}[t]
\includegraphics[scale=1.0]{CARMA-STITCH.jpg}
%\includegraphics[scale=0.7]{CARMA_23_teuben.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   The CARMA 23-element interferometer at Cedar Flat.
 Heterogeneous array with six 10 m,  nine 6 m, and eight 3.5 m antennas
 providing projected antenna spacings from 3.5 m to 2 km.
 Receivers at 1cm,  3mm, and 1.3 mm.  4 GHz bandwidth correlator
 providing 16 spectral windows.  Used for imaging star formation regions,
 galaxies, planets, protoplanetary disks,  molecular clouds, galaxy clusters.
  Recent 1.3 mm VLBI using telescopes in Arizona,  California and Hawaii with 
 phased arrays at CARMA and SMA detected 30 microarcsec structure in the
 4 million solar mass Black hole at the Galactic center.}
\vskip -0.2in
\end{figure*}


\begin{figure*}[t]
\includegraphics[scale=1.0]{koda.png}
\caption{CO images of nearby spiral galaxies observed with
CARMA by Koda et al.  Most were observed with a 19 point mosaic, providing a
field of view of 2.3 arcmin and a resolution of 3 arcsec.}
\end{figure*}


\begin{figure*}[t]
\includegraphics[scale=0.7]{20cm-HCN-OH-NH3.pdf}
\caption{HCN, OH, NH3 emission in the Galactic center. BIMA and VLA  19 point mosaic images} 
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=0.8]{OriSpectra.pdf}
\caption{1.3 mm continuum map of Orion-KL, with spectra of Source I and BN.
Red contours (18--320 mJy/beam) show a $0.25''$ resolution map;
halftone image is with $0.85''$ resolution.  The H30$\alpha$
recombination line is prominent in the spectrum of BN, but isn't
detected toward Source~I.  A vibrationally excited transition of
water is, however, detected in Source~I for the first time.} 
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=0.8]{PairedAntenna.jpg}
\caption{  Paired Antenna Calibration System using 3.5 m antennas at 30 GHz.  
    The 3.5~m antennas are paired
with 6.1 and 10.4~m antennas making science observations at millimeter wavelengths.
The 3.5~m antennas simultaneously observe calibration sources in the 1 cm band.
For calibration sources within a few degrees, the millimeter wavelength observations
of the science target source, and the observations of the calibrator at 1cm, sample
similar atmospheric phase fluctuations, allowing us to correct for the  atmospheric phase fluctuations on long baselines at millimeter wavelengths.}
\end{figure*}

\end{document}


\begin{figure*}[t]
\includegraphics[scale=0.8]{ic342.pdf}
\caption{IC342 and it's companion, UGCA 86, which has a tail of HI extending towards IC342. There are three images - a moment 0 map, a moment 1 map and channel maps. Note that only half of IC 342 appears in the moment maps since the other half lies within the velocities of the Milky Way HI (as seen in the channel maps). Allen Telescope Array; Amber Bauermeister, UCB.}
\end{figure*}

\begin{figure*}[t]
\includegraphics[scale=0.8]{ngc2403-2366.pdf}
\caption{NGC 2403 and NGC 2366 individually (a pair of galaxies - we did a pointing on each). NGC 2366 has a new HI detection right next to it, but 800 km/s faster (likely a superposition).
 Allen Telescope Array; Amber Bauermeister, UCB.}
\end{figure*}



\begin{figure*}[t]
\includegraphics[scale=0.8]{m106.pdf}
\caption{M106 group - a large group of galaxies. This document has  moment 0 and moment 1 maps, with the galaxies labeled, as well as a figure showing the stream of gas we detected (not previously seen!) coming off of NGC 4288 in the direction of M106. Allen Telescope Array; Amber Bauermeister, UCB.}
\end{figure*}

 
\item EHT is a  network of  $\lambda$ (sub)mm  antennas to make a Global VLBI array. 
\item At  $\lambda$ 1.3mm and 0.8mm,  angular resolution $\sim$ 20 micro $\mu as$
\item SgrA* and M87 have the  largest apparent BH  Event Horizons.
\subitem  General Relativity in the strong-field regime.
\subitem  Accretion and outflow at the edge of a BH.
\item SgrA*  $\sim 4~10^6  M_0 $  BH at Galactic Center. 
\subitem We resolve structures on scale  of  Event Horizon.  
\item  M87  giant elliptical galaxy with $\sim 8~10^9  M_0 $  BH in nucleus.
\subitem  We detect structure at the base  of  relativistic jet.
\item  EHT  Roadmap  2010 - 2015;  critical contribution of CARMA.  
\end{itemize}

\clearpage

\section*{SgrA* Evidence for a Black Hole}
\slshape
\item  Evidence suggests SgrA* is a $4~10^6$ solar mass black hole at the galactic center:
\item  Mass estimates from orbitting stars (Gillessen et.al 2008, Ghez. et el. 2008),
\item Proper motion limits on SgrA* itself (Backer \& Sramek 1999, Reid \& Brunthaler 2004).
\item Size limits on SgrA* from VLBI (Bower et al.  2004, Shen et al. 2005, Doeleman et al. 2008). 
\item The observations imply a mass density for SgrA*  $ > ~9~10^{22} M_0$  per cubic parsec. 
\item Close observational correlation between the mass of our galaxy and it's
velocity dispersion suggest strong connection between formation of the black hole and the galaxy itself.
\item The best evidence thus far is from studying the proper motion of stars near SgrA*. 
\item  EHT will increase our understanding and add to the mounting evidence for a Massive Black Hole at the
Galactic center.
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.6]{star-orbits2.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   Star orbits
   \label{fig:star-orbits2}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\section*{The Event Horizon Telescope}
\item The EHT is a  network of (sub)mm
wavelength antennas that are linked together to function as a Global VLBI array.
\item At  $\lambda  1.3 mm $, the angular resolution of the
EHT $\sim$ 20 micro arcseconds.
\item Need $\lambda mm$  observations to minimize dispersion by the Inter-Stellar Medium which goes as $\lambda^2$.
\item For SgrA*, the $4~10^6 M_0 $ black
hole at the Galactic Center, the EHT  has resolved structures on  scale of the Event Horizon.  
\item Similar scale structures have also been detected at the base of the relativistic jet in M87, a giant
elliptical galaxy harboring a $\sim 10^9 M_0$ black hole.
\item Currently IBOB and BEE2 boards and CASPER firmware are used to phase up and process the signals from the antennas, then pass the data to the Mark VB data recorder.
\item Closure phase ($ O = \phi_1 + \phi_2 - \phi_3$) is used for calibration as phase errors are subtracted out.
\item  2007-2010  SgrA* observations with ARO/SMT, CARMA, and JCMT  estimated Schwarzschild radius ~$0.37 AU$.
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.76]{vlbi-overview.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   VLBI overview
   \label{fig:vlbi-overview}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.3]{carma-moon.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   CARMA MOON 
   \label{fig:carma-moon}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.5]{croppedsmapan.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   JCMT and SMA telescopes on Mauna Kea
   \label{fig:sma}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.6]{maserphoto.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   VLBI maser 
   \label{fig:maser}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage


\section*{CASPER Libraries and Hardware}
\slshape
\item CASPER (Collaboration for Astronomical Signal Processing and Engineering Research.)
\item FPGA based hardware is now used in phasing up the antennas with 1 GHz Bandwidth
\item The system design uses modular DSP
boards with a flexible interconnect architecture which allows 
reconfiguration of the computing resources for multiple applications.
\item The programming model uses a system generation library with
hardware abstractions which allow the application programmer to focus
on the application rather than the details of the hardware.
\item The system design and programming model together allow the application
software to survive by using a technology independent design flow.
.
\item Scalable CASPER technology allows for the phased arrays  that improve sensitivty .
\item Next generation architecture of the broadband phased array processor upgrade
based on the ROACH Virtex-5, is targeted for deployment in 2012.
\item This will allow double the bandwidth and increased sensitivity.

\vspace{1pc}
\slshape
\includegraphics[scale=0.3]{sma-hw-diagram.pdf}
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -1.0in
\includegraphics[scale=0.9]{CARMA_network_layout.pdf}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   CARMA Mark5B, DBE, and Network Setup 
   used for the uVLBI experiment held March 26th 2009 through April 8th 2009 at CARMA.
   \label{fig:CARMA_network_layout.pdf}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage


\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=1.28]{SgrA-BH-sim.pdf}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   SgrA Results and Black Hole models:  Solid black line is apparent diameter with lensing by a black hole.
Dashed line with no lensing. The intrinsic size of SgrA* observed with  $\lambda 1.3mm $ VLBI  (red line) is smaller than the minimum apparent size of the black hole event
 horizon suggesting that the submm emission of SgrA* must be offset from the black hole position.
 This can be understood in the context of General relativistic MHD accretion disk simulations
(right), which exhibit compact regions of emissions due to Doppler enhancement of the approaching side of an accretion disk.
   \label{fig:SgrA-BH-sim}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\begin{figure*}[t]
\begin{center}
\includegraphics[scale=1.0]{Sgra-BlackHole.pdf}
\caption{\small
   \setlength{\baselineskip}{0.7\baselineskip} 
 \label{fig:SgrA Black Hole}
}
\end{center}
\vskip -0.2in
\end{figure*}

\section*{What did we see?}
\slshape

\item A symmetric emitting surface surrounding a black hole is gravitationally lensed to appear larger than its true diameter. 
%\item  The solid black line shows the apparent diameter with lensing by a black hole.
%\item  The dashed line with no lensing.
\item The intrinsic size of SgrA* observed with $\lambda 1.3mm$ VLBI  is smaller than the minimum apparent
size of the black hole event horizon suggesting that the submm emission of SgrA* must be offset from the
black hole position.  
\item This can be understood in the context of General relativistic MHD accretion disk simulations, which exhibit compact regions of emissions due to Doppler enhancement of the approaching side of an accretion disk.
\clearpage

\section*{What should we see?}
\slshape
\item VLBI simulations of SgrA* have given us a good idea of what to expect from imaging.
\item  Left:  models that have been scatter broadened by the Inter Stellar Medium.
\item Middle: images reconstructed using a 7-station $\lambda=0.8mm$ wavelength
array that could reasonably scheduled within the next 3-5 years.
\item Right:  images reconstructed using 13-station array that could be assembled  this decade.

\vspace{1pc}

\slshape
\includegraphics[scale=0.5]{vlbi-sim.jpg}

\clearpage


\section*{Improving Sensitivity}

\item Enhancing EHT sensitivity: dual polarization, phased arrays, wideband VLBI backends,
and high-speed VLBI recorders.
\item Time-variable changes can be resolved and monitored on 10-second time scales.  
\item Simulations model flares in
SgrA* as orbiting hot-spots in the accretion flow, EHT can potentially
time these orbits and provide new estimates of the black hole spin.
\item Planned upgrade to SMA and CARMA this year will allow us to form beams at these locations, improving the image
and sensitivity from the 2007-2009  observations.
\item ALMA will be phased up and contributing to the EHT within a few years.
\clearpage

\begin{figure*}[t]
\begin{center}
\vskip -0.2in
\includegraphics[scale=0.16]{EArray424KB.jpg}
\caption{\small
   \setlength{\baselineskip}{0.85\baselineskip}
   E-configuration
   \label{fig:E-configuration}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\begin{figure*}[t]
\begin{center}
\includegraphics[scale=3.1]{Closure-Phase-D230-apex.jpg}
\caption{\small
   \setlength{\baselineskip}{0.8\baselineskip}
   Closure Phase with APEX
 \label{fig:SgrA Closure Phase}
}
\end{center}
\vskip -0.2in
\end{figure*}

\begin{figure*}[t]
\begin{center}
\includegraphics[scale=3.1]{Closure-Phase-D230-alma10.jpg}
\caption{\small
   \setlength{\baselineskip}{0.8\baselineskip}
   Closure Phase with ALMA10
 \label{fig:SgrA Closure Phase}
}
\end{center}
\vskip -0.2in
\end{figure*}


\begin{figure*}[t]
\begin{center}
\includegraphics[scale=3.1]{Closure-Phase-D230-alma50.jpg}
\caption{\small
   \setlength{\baselineskip}{0.8\baselineskip}
   Closure Phase with ALMA50
 \label{fig:SgrA Closure Phase}
}
\end{center}
\vskip -0.2in
\end{figure*}
\clearpage

\section*{STATION CALIBRATION}

\item    Correlated flux on VLBI target source = 
\subitem correlation coeficient
                x sqrt(Ta/Tsys(i) Ta/Tsys(j))
                x phasing efficiency

\item  $ T_a$  on target source: SgrA* in complex FoV.
\subitem  phasing efficiency: atmospheric phase;  pointing errors; wind.

\item    Real time calibration of array stations using station correlator.
\subitem  Need good station uvcoverage to isolate and calibrate target source.
\subitem  Use extended array configurations to
spatially filter out large scale structure if atmospheric phase correction is good enough.

 \item     High instantaneous bandwidth. (Maximum atmospheric correlation time $\sim 10 s$)
\clearpage

\section*{ROADMAP FOR MMVLBI}
%\begin{itemize}
\item 2008-2010:   500 MHz band on 1-2 antennas at CARMA. 
\subitem  Analog input into ADC for each antenna in VLBI station.
\subitem  Custom formatting into VLBI recorder.

\item  2011-2012  Two 500 MHz bands.
\subitem  digital beamforming at single phase center.
\subitem use CARMA correlator for  beamformer  calibration.
\subitem  Custom formatting into VLBI recorder.
\subitem      (e.g. CARMA  4-8 antennas x 2 pols x 4 500 MHz bands)
  
\item 2015+ High speed digitized data for each antenna in VLBI station.
\subitem frequency domain delay and fringe rate correction.
\subitem  digital beamforming at multiple phase centers. 
\subitem use station correlators for  beamformer  calibration.
\subitem  industry standard data to disk. (e.g. 10GbE)
\subitem       (e.g. CARMA  15 antennas x 2 pols x 8 GHz) 
      
\clearpage

\section*{ MMVLBI  with ALMA}

\item 2010-2012   Limited station commitment to VLBI .
\subitem Typical 1 week/year.
 \subitem No ALMA participation.

\item 2015+      Major station committment to VLBI with ALMA
\subitem VLBI as a science motivation for maintaining university facilities.
\subitem  2 sessions (e.g. Spring and Fall) 
\subitem  1-2 week gap to reduce data and mitigate bad weather.
\item  Heterogeneous VLBI stations

\subitem  Long Term Plan to align station capabilities.
\item  Frequency, Pols x Bandwidth. 
\subitem  CARMA 230 GHz x 2 pols. Analog data from antennas.
\subitem  SMA   230 GHz x 1 pol;  345 GHz x 2 pols. Analog data from antennas.
\subitem  ALMA  230 GHz and 345 GHz dual polarization.  2 Ghz digital data from antennas.
\clearpage
     
 \section*{CONCLUSION}
\item  VLBI using CARMA,  JCMT and  ARO/SMT on Mt. Graham in Arizona  at 1.3mm.
\subitem  We resolve structures on scale  of  Event Horizon.
\subitem  SgrA* emission varies over a  few hours on scales of several Schwarzschild radii.  
\item Simulations model flares in SgrA* as orbiting Ôhot-spotsÕ in the accretion flow.
\item  EHT adds  DSP  to  existing (sub)mm facilities for  VLBI  
\item  Phased arrays, wideband backends,  and high-speed recorders can  monitor 10-s  time scales.
\item  EHT can  time these orbits and provide estimates of black hole spin.  
\item M87:  Size constrains  jet formation and 
production of TeV photons observed with Fermi Gamma-ray satellite.  
\item  EHT  bring us as close to the edge of BH  as we are likely to come for decades.
\end{itemize}
\end{document}  
