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\@writefile{toc}{\contentsline {chapter}{\numberline {1}INTRODUCTION}{2}}
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\@writefile{toc}{\contentsline {chapter}{\numberline {2}TECHNICAL OVERVIEW}{4}}
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\@writefile{toc}{\contentsline {section}{\numberline {2.1}Primary Goals for the VLA Expansion}{4}}
\@writefile{toc}{\contentsline {section}{\numberline {2.2}Components of the Upgrade}{5}}
\@writefile{toc}{\contentsline {subsection}{\numberline {2.2.1}The Ultra-Sensitive Array}{5}}
\@writefile{lof}{\contentsline {figure}{\numberline {2.1}{\ignorespaces The current (+) and predicted (o) continuum (left) and spectral line (right) sensitivity of the VLA after the upgrade. For both panels, a 12-hour observation with 27 antennas and with the efficiencies and system temperatures listed in Table 2.3\hbox {} are assumed. The continuum sensitivity assumes bandwidths given in Table 2.3\hbox {}, while the line sensitivity is based on a bandwidth equivalent to 1 \penalty \@M \ km\penalty \@M \ s$^{-1}$. (Note the different vertical scales.) For the {\bf  A+} configuration and 37 antennas, the sensitivity would be improved by a further factor of 1.33. To illustrate the {\it  relative} sensitivities of the proposed new bands for nonthermal and thermal objects, the left panel also shows the {\it  slopes} of a typical synchrotron spectrum (dashed) and of an optically thick thermal spectrum (dotted). The vertical placement of these spectra is arbitrary.}}{6}}
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\@writefile{toc}{\contentsline {subsection}{\numberline {2.2.2}The A+ Configuration}{7}}
\@writefile{toc}{\contentsline {section}{\numberline {2.3}Antenna and Receiver Improvements}{7}}
\@writefile{toc}{\contentsline {subsection}{\numberline {2.3.1}Improved Low Noise Receivers}{7}}
\@writefile{toc}{\contentsline {subsection}{\numberline {2.3.2}New Observing Bands at the Cassegrain Focus}{8}}
\@writefile{lot}{\contentsline {table}{\numberline {2.1}{\ignorespaces Proposed VLA Cassegrain Observing Bands}}{8}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.2}{\ignorespaces A possible arrangement of eight Cassegrain feeds around the secondary focus circle.}}{8}}
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\@writefile{toc}{\contentsline {subsection}{\numberline {2.3.3}New Prime Focus Systems}{9}}
\@writefile{lof}{\contentsline {figure}{\numberline {2.3}{\ignorespaces A sketch of the modified quadrupod and rotating feed assembly at the prime focus. The horizontal quadrupod legs would be replaced with narrow tubes, allowing the subreflector to be rotated away from the prime focus about a vertical axis and exchanged for any of four potential UHF feeds (shown in outline).}}{9}}
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\@writefile{toc}{\contentsline {subsection}{\numberline {2.3.4}Sensitivity Goals}{9}}
\@writefile{lot}{\contentsline {table}{\numberline {2.2}{\ignorespaces Potential Prime Focus Observing Bands}}{10}}
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\@writefile{lot}{\contentsline {table}{\numberline {2.3}{\ignorespaces VLA Expansion\ Sensitivity Goals for 12-hr Synthesis}}{10}}
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\@writefile{toc}{\contentsline {section}{\numberline {2.4}A New LO/IF Transmission System}{10}}
\@writefile{toc}{\contentsline {section}{\numberline {2.5}A New Correlator}{10}}
\@writefile{lot}{\contentsline {table}{\numberline {2.4}{\ignorespaces Maximum Channels in Current VLA Spectral Line Modes}}{11}}
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\@writefile{lot}{\contentsline {table}{\numberline {2.5}{\ignorespaces Sizes of Synthesis Correlators}}{11}}
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\@writefile{lot}{\contentsline {table}{\numberline {2.6}{\ignorespaces Bandwidths and number of channels}}{12}}
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\@writefile{toc}{\contentsline {section}{\numberline {2.6}Improved Surface-Brightness Sensitivity}{13}}
\@writefile{lof}{\contentsline {figure}{\numberline {2.4}{\ignorespaces Examples of possible E configurations: the E1 (left) requires only 9 new antenna stations and two new rail spurs; the E2 (right) requires 27 new stations and five or six new spurs.}}{13}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.5}{\ignorespaces Relative sensitivities of the D, E1 and E2 configurations.}}{14}}
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\@writefile{toc}{\contentsline {section}{\numberline {2.7}High Angular Resolution---The A+ Configuration}{15}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.6}{\ignorespaces The frequency-resolution coverage of the VLA (dark) and VLBA (shaded). The sloping ``VLA-VLBA Gap'' is caused by the absence of antennas with separations between 35 and 250 km. Much astrophysical analysis depends on imaging at fixed angular resolution over a wide frequency range, {\it  i.e.},\penalty \@M \ on {\it  vertical} lines in this diagram. The ``gap'' seriously restricts interpretative work at resolutions from a few hundred milli-arcseconds to one arcsecond.}}{15}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.7}{\ignorespaces Possible antenna locations for a six-antenna A+ configuration, as suggested in the VLA Development Plan\ (1995). Four new antennas are added, at Dusty, Bernardo and Vaughn in New Mexico and at Holbrook, in Arizona. }}{16}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.8}{\ignorespaces Possible antenna locations for a ten-antenna A+ configuration. Eight new antennas are added in this configuration, at Dusty and Bernardo for the inner ring, and at Vaughn, Carrizozo, Truth Or Consequences, Red Hill, Gallup and Bloomfield for the outer ring. This arrangement results in much better imaging performance than the six-antenna arrangement shown in Fig.\penalty \@M \ 2.7\hbox {}. }}{17}}
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\@writefile{toc}{\contentsline {subsection}{\numberline {2.7.1}Example imaging with the A+ configuration}{18}}
\@writefile{lof}{\contentsline {figure}{\numberline {2.9}{\ignorespaces (left) The supernova remnant Cassiopeia A, rescaled to a distance of 800\penalty \@M \ kpc, (right) as imaged with the present VLA in the A configuration at $\lambda $5cm, (FWHM $\sim $ $0.3''$) giving only a rudimentary indication of shell structure. }}{18}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.10}{\ignorespaces Cassiopeia A rescaled to 800\penalty \@M \ kpc distance, as imaged at $\lambda $5cm with (left) the proposed 6-element A+ configuration (four new antennas), (right) the proposed ten-element A+ configuration (eight new antennas). Contours are shown at -1.4, 1.4, 3.5, 7, 14, 21, 28, 35 and 42\penalty \@M \ $\mu $Jy\ per beam. }}{19}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2.11}{\ignorespaces  The differences between the model image and the reconstructed images of the scaled Cassiopeia A remnant shown in Figure 2.9\hbox {}. The rms residuals within the source for the six-element A+ configuration (four new antennas) are about three times larger than for the ten-element A+ configuration (eight new antennas), and the largest localized errors are ten times the off-source ``noise''. }}{20}}
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\@writefile{toc}{\contentsline {section}{\numberline {2.8}On-Line Computing}{21}}
\@writefile{toc}{\contentsline {section}{\numberline {2.9}Other Capabilities}{21}}
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\@writefile{toc}{\contentsline {chapter}{\numberline {3}NEW SCIENCE WITH THE ENHANCED VLA}{22}}
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\@writefile{toc}{\contentsline {section}{\numberline {3.1}Imaging-Spectroscopy of Solar Radio Bursts}{22}}
\@writefile{toc}{\contentsline {section}{\numberline {3.2}Bistatic Radar Observations of Planets and Minor Bodies}{22}}
\@writefile{toc}{\contentsline {section}{\numberline {3.3}High-resolution Imaging of Thermal Emission}{23}}
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\@writefile{toc}{\contentsline {section}{\numberline {3.4}Imaging Protoplanetary Disks}{23}}
\@writefile{toc}{\contentsline {section}{\numberline {3.5}Transient Phenomena}{24}}
\@writefile{toc}{\contentsline {section}{\numberline {3.6}Extragalactic \hbox {H\hskip 1truept{\sc  i} }Surveys}{24}}
\@writefile{toc}{\contentsline {section}{\numberline {3.7}Clusters of Galaxies}{25}}
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\@writefile{toc}{\contentsline {section}{\numberline {3.8}Objects at High Redshift}{25}}
\@writefile{toc}{\contentsline {chapter}{\numberline {4}IMPACT ON SCIENCE WITH THE VLBA}{26}}
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\@writefile{toc}{\contentsline {section}{\numberline {4.1}Improved Image Quality}{26}}
\@writefile{toc}{\contentsline {section}{\numberline {4.2}Closing the Coverage Gap}{26}}
\@writefile{toc}{\contentsline {section}{\numberline {4.3}Extended Scaled-Array Capability}{27}}
\@writefile{toc}{\contentsline {section}{\numberline {4.4}Snapshot Mode}{27}}
\@writefile{toc}{\contentsline {section}{\numberline {4.5}Synergy}{27}}
\@writefile{lof}{\contentsline {figure}{\numberline {4.1}{\ignorespaces  (upper left) The supernova remnant Cassiopeia A, rescaled to a distance of 800 kpc (M31), at 8 milli-arcseconds resolution. (upper right) An image obtained by sampling this structure with the {\it  u-v}\penalty \@M \ coverage of the present VLBA alone at $\lambda $21cm and 30$^\circ $\ declination. Only the most compact emission is represented at all; the diffuse ring and ``plateau" emission are resolved out and scattered into large-scale fringes. (lower left) An image obtained by sampling this structure with the {\it  u-v}\penalty \@M \ coverage of the present VLBA and one VLA antenna at $\lambda $21cm and 30$^\circ $\ declination. The more diffuse emission is detected, but its brightness distribution is poorly represented. (lower right) An image obtained with the {\it  u-v}\penalty \@M \ coverage of the array shown in Figure\penalty \@M \ 2.7\hbox {}, with four new antennas and one VLA antenna added to the VLBA at $\lambda $21cm and 30$^\circ $\ declination. All of the major emission is now correctly located. For this specific example, the image obtained with eight new antennas as shown in Figure\penalty \@M \  2.8\hbox {} is only marginally better. }}{29}}
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