\documentclass[preprint]{aastex} % AASTeXv5.0
\usepackage{carma_memo}

\begin{document}

%%
%% CARMA Memo number. Check web http://www.mmarray.org/memos
%% for most recent memo number.
%%
\carmamemo{xx} 	

%%
%% Uncomment these if this is also an ALMA or BIMA memorandum.
%%
%\almamemo{222} % ALMA Memo number.
%\bimamemo{xx} % BIMA Memo number.

\title{Antenna Configuration Evaluation}

\author{Melvyn Wright}
\affil{Radio Astronomy laboratory, University of California, Berkeley,
    CA, 94720}
%% List additional authors in the same way.
%\author{Sarah F. Theorist}
%\affil{Lunar College}

\begin{abstract}

In this memo we show that the array performance is improved by
eliminating two stations, reducing the costs of stations, power and
fiber connections and roads, and time spent in antenna
reconfigurations.
The modified C configuration uses
station 57 instead of station 33 which was only used in CARMA C
configuration.
The modified A configuration
uses station 20 from the B configuration instead of station 8 which was
only used in the A configuration. 
For each configuration we simulated observations from -2 to +2 hours
sampled at 36 sec intervals. In practice, observations will be
interrupted by calibrations and not sampled symmetrically about transit.
The effects of the proposed changes are smaller than the effect of the
heterogeneous antenna sizes, different weighting, and non optimum
sampling of the data.
We eliminate a
NS station and a section of the loop road and power and fiber
distribution.
The modified A configuration has a shorter minimum uv
spacing and more overlap with the B configuration, allowing better calibration
between A and B configurations and more reliable estimates of decorrelation from
atmospheric turbulence.

\end{abstract}

%%
%% Change Record/Revision History
%% This goes AFTER the abstract: the abstract is
%% printed on the front of the cover page and the 
%% change record on the back of the cover page.
%% Use \addrevision to add additional revisions.
%% Columns are 
%% | revision |date| author| sections/pages affected |
%% |          | remarks                              | 

\ChangeRecordBegin
\addrevision{1.0}{2004-Mar-24}{MCHW}{1-10}{Original email text mailed to CARMA working group}
\addrevision{1.1}{2004-Apr-07}{MCHW}{1-10}{Added tables for heterogeneous arrays}
\addrevision{1.2}{2004-Apr-28}{MCHW}{1-1}{improved abstract}
\addrevision{1.3}{2004-Apr-29}{MCHW}{1-10}{submitted as CARMA memo}
\ChangeRecordEnd


\section{Introduction}

The current CARMA A configuration for 15 antennas uses 4 stations
to the east of highway 168 to provide large east-west baselines.
These four stations need long fiber runs and separate roadway and power
infrastructure. In this memo we explore alternative antenna
configurations using stations on the west side of highway 168.

Antenna configurations for Cedar Flat are based on
studies of the uv-coverage and synthesised beam characteristics
obtained with 15 antennas (CARMA memos 19, 20)
Changes to the antenna configuration were required to accommodate the
boundaries and topography of the chosen site, and a revised center
location for the CARMA C/D/E arrays was chosen (CARMA memo 23)
In memo 25 we showed that the array performance was not significantly
changed by eliminating two stations.


\section{Results}

alternatve_A.beams.results.20mar06
compares beam widths, sensitivities, sidelobes,
shadowing and uvrange for:

# A.ant  CARMA-15  A-configuration with station 20 instead of 8
# B.ant  CARMA-15  B-configuration using station 16-30
# B+18.ant  CARMA A+B configuration. 18-antenna without stations 1-5
# B+.ant  CARMA-15  A-configuration without stations 1-4
# B+30-5.ant  CARMA-15  A-configuration without stations 1-5


A and B are "standard".

B+18 is an 18-antenna configuration without stations 1-5. This shows
what might be done with a few more antennas on A and B stations
rather than clustered as in the EZ, DZ and CZ that I looked at
before in memo 25 and 27.

B+ is an A-configuration without stations 1-4
B+30-5 is an A-configuration without stations 1-5 (B+ 30, omit 5)

These last two were the contenders as an alternative A configuration.

B+30-5.ant  has better sidelobes and brightness sensitivity.
Bes an analysis of alternative A array configuarions
 without stations 1-4.

. Main conclusion is that better beams are obtained by also omitting
station 5. Better sidelobes and brightness sensitivity.

. Station 5 was located to fill the gap between 1-4 and 6-15.
and is logically part of this A configuration.

. Defer building station 5 until stations 1-4 are built.

. If stations 1-4 are not built, we should re-evaluate the
best location for additional stations (if any) in the light
of experience using the 15-antenna array and possibility
of using 3.5 m antennas in 23-antenna configurations.
30-5 has more complete uv sampling which makes it more robust
to missing data. Table 5 compares the beam widths and brightness sensitivity using different weightings of the uvdata.
The resolution is enhanced using robust weighting. Table 5
shows the loss in brightness sensitivity which also favors
the B+30-5 configuation.


The array configurations and results are all in
http://astron.berkeley.edu/~wright/carma/config

I suppose I should put these results
into another memo.



We compare the performance of the original and modified CARMA configurations.

The fitting procedures are simple {\bf unix csh} scripts which control
{\bf MIRIAD} tasks. (CARMA memo 5). 
These scripts are similar to those used for ALMA and ATA simulations,
but are slightly more complex because of the different antenna sizes
used in the heterogeneous CARMA telescope.
The script generates uv-data for a point source with thermal and
atmospheric phase noise, does a phase calibration, and makes an image
and beam. A Gaussian fit is made to the synthesised beam, and the
results written into a table.  The brightness sensitivity, beam FWHM,
and residual sidelobe level after the fit are calculated.
In addition the script plots the uvcoverage and beam
where one can inspect the 2D uvcoverage and sidelobe distribution.


Table 1 lists the synthesized beam FWHM, brightness sensitivity, Tb rms, synthesized beam
sidelobe levels, fraction of unshadowed data used in synthesized beam, Nvis,
and $uv$ range for declinations 30, 0 and -30 for the current
configurations.  

Table 2 compares the current and modified CARMA C configuration using
station 57 instead of station 33 which was only used in CARMA C
configuration. The beam characteristics are listed for the original and modified (Cp)
configuration for declinations 45, 30, 15, 0, -15, and -30 degrees.

The original and modified beam FWHM are the same within 0.01 arcsec,
the uvrange is the same, and the sidelobe levels are better for 4 of
the 6 sampled declinations.

Table 3 compares the current and modified CARMA (Ap) configuration which
uses station 20 from the B configuration instead of station 8 which was
only used in the A configuration.  Here, the goal was to eliminate a
NS station and a section of the loop road and power and fiber
distribution.

The change in the beam shape and sidelobe levels is again
very small. The modified A configuration has a shorter minimum uv
spacing and more overlap with the B configuration. Both these features
have proved desirable from experience with the BIMA long baselines.
The beam is rounder at all declinations, and the brightness sensitivity
10\% better at high declination.


Table 4 and 5 list the beam characteristics for the CARMA
configurations when the stations are populated with 6 and 10m antennas
in two different ways.
In Table 4 the first 6 antennas are 10m and the last 9 are 6m.
In Table 5 the last 6 antennas are 10m and the first 9 are 6m.

For each configuration we simulated observations from -2 to +2 hours
sampled at 36 sec intervals. In practice, observations will be
interrupted by calibrations and not sampled symmetrically about transit.

The effects of the proposed changes are smaller than the effect of the
heterogeneous antenna sizes, different weighting, and non optimum
sampling of the data.


\section{Conclusion}

In this memo we show that the beam characteristics are not significantly changed
by eliminating two stations. 
The modified C configuration uses
station 57 instead of station 33 which was only used in CARMA C
configuration.
The modified A configuration 
uses station 20 from the B configuration instead of station 8 which was
only used in the A configuration.  We eliminate a
NS station and a section of the loop road and power and fiber
distribution.
The modified A configuration has a shorter minimum uv
spacing and more overlap with the B configuration, allowing better calibration
between A and B configurations and more reliable estimates of decorrelation from
atmospheric turbulence.

Overall the array performance is improved by reducing the costs of stations, power and
fiber connections and roads, and time spent in antenna
reconfigurations.

\begin{references}

CARMA memo 5, Compact Configuration Evaluation for CARMA, Melvyn Wright,  Sep 2002

CARMA memo 19, Version 1 CARMA Configurations for Cedar Flat, Tamera Helfer and Melvyn Wright, February 2004.

CARMA memo 20, Version 2 CARMA Configurations for Cedar Flat, Tamera Helfer, February 2004.

CARMA memo 23, Lots in Translation: A Revised Center Location for the CARMA C/D/E Arrays, Glen Petitpas, March 2004.

CARMA memo 25, Antenna Configuration Evaluation, Melvyn Wright,  Sep 2002

\end{references}

\begin{table}
\tablenum{1}
\centering
\caption{current configurations}
\smallskip
\begin{tabular}{cccccccccccccccc}
\hline
\hline
Config & DEC & HA & Rms & FWHM &Tb rms &  & Sidelobe[\%] &   & Nvis & uvrange \\ \hline
   & degrees & [hrs] & [mJy] & [arcsec] &[mK] &  Rms & Max & Min & [\%] & [m] \\ \hline
A &  30 &  -2,2,.01 &  0.23 & 0.15 x 0.12 &  295.4    &    1.8 &   9.3 &   -7.0 &  100 & 181 & 1886 \\
B &  30 &  -2,2,.01 &  0.23 & 0.37 x 0.30 &   47.9    &    2.1 &  10.9 &   -6.9 &  100 &  82 &  946 \\
C &  30 &  -2,2,.01 &  0.23 & 0.91 x 0.75 &    7.8    &    2.0 &  10.0 &   -6.0 &  100 &  25 &  373 \\
D &  30 &  -2,2,.01 &  0.23 & 2.22 x 1.91 &    1.3    &    2.0 &  10.0 &   -6.2 &  100 &  10 &  149 \\
E &  30 &  -2,2,.01 &  0.23 & 4.49 x 3.95 &    0.3    &    1.9 &   8.8 &   -6.7 &  100 &   8 &   66 \\ \hline
A &   0 &  -2,2,.01 &  0.27 & 0.16 x 0.15 &  260.1    &    2.5 &  29.3 &   -7.1 &  100 & 144 & 1833 \\
B &   0 &  -2,2,.01 &  0.27 & 0.38 x 0.37 &   44.4    &    2.6 &  27.1 &  -11.6 &  100 &  65 &  899 \\
C &   0 &  -2,2,.01 &  0.27 & 0.94 x 0.91 &    7.3    &    2.6 &  34.5 &   -8.0 &  100 &  18 &  324 \\
D &   0 &  -2,2,.01 &  0.27 & 2.39 x 2.22 &    1.2    &    2.6 &  29.5 &   -9.6 &  100 &   8 &  129 \\
E &   0 &  -2,2,.01 &  0.27 & 5.00 x 4.44 &    0.3    &    2.6 &  47.0 &   -9.5 &  100 &   6 &   65 \\ \hline
A & -30 &  -2,2,.01 &  0.56 & 0.32 x 0.15 &  269.7    &    1.8 &   9.0 &   -6.7 &  100 &  62 & 1692 \\
B & -30 &  -2,2,.01 &  0.56 & 0.76 x 0.38 &   44.8    &    1.7 &   9.1 &   -6.6 &  100 &  31 &  809 \\
C & -30 &  -2,2,.01 &  0.56 & 1.89 x 0.93 &    7.4    &    1.7 &   8.8 &   -6.3 &  100 &  10 &  284 \\
D & -30 &  -2,2,.01 &  0.57 & 4.73 x 2.25 &    1.2    &    1.7 &   8.4 &   -6.5 &   96 &   5 &  113 \\
E & -30 &  -2,2,.01 &  0.80 & 8.53 x 3.87 &    0.6    &    2.3 &  14.5 &   -9.0 &   49 &   3 &   56 \\ \hline
\end{tabular}
\raggedright\smallskip
\end{table}


\begin{table}
\tablenum{2}
\centering
\caption{Modified CARMA (Cp) configuration using station 57 instead of station 33}
\smallskip
\begin{tabular}{cccccccccccccccc}
\hline
\hline
Config & DEC & HA & Rms & FWHM &Tb rms &  & Sidelobe[\%] &   & Nvis & uvrange \\ \hline
   & degrees & [hrs] & [mJy] & [arcsec] &[mK] &  Rms & Max & Min & [\%] & [m] \\ \hline
C  & 45 &  -2,2,.01 &  0.23 & 0.91 x 0.75  &   7.8   &     1.8 &  11.7 &  -5.9 &  100 &  24&  369 \\
Cp & 45 &  -2,2,.01 &  0.23 & 0.90 x 0.75  &   7.9   &     1.8 &  11.1 &  -5.9 &  100 &  24&  369 \\
C  & 30 &  -2,2,.01 &  0.23 & 0.91 x 0.75  &   7.8   &     2.0 &  10.0 &  -6.0 &  100 &  25&  373 \\
Cp & 30 &  -2,2,.01 &  0.23 & 0.90 x 0.75  &   7.9   &     2.0 &   9.1 &  -6.3 &  100 &  25&  373 \\
C  & 15 &  -2,2,.01 &  0.24 & 0.91 x 0.81  &   7.5   &     2.2 &  12.1 &  -6.8 &  100 &  22&  359 \\
Cp & 15 &  -2,2,.01 &  0.24 & 0.90 x 0.80  &   7.7   &     2.2 &  13.1 &  -7.1 &  100 &  22&  359 \\
C  &  0 &  -2,2,.01 &  0.27 & 0.94 x 0.91  &   7.3   &     2.6 &  34.5 &  -8.0 &  100 &  18&  324 \\
Cp &  0 &  -2,2,.01 &  0.27 & 0.94 x 0.90  &   7.4   &     2.6 &  30.6 &  -8.3 &  100 &  18&  324 \\
C  &-15 &  -2,2,.01 &  0.34 & 1.22 x 0.91  &   7.1   &     2.0 &   9.8 &  -6.2 &  100 &  14&  305 \\
Cp &-15 &  -2,2,.01 &  0.34 & 1.21 x 0.91  &   7.1   &     2.0 &  12.0 &  -6.4 &  100 &  14&  305 \\
C  &-30 &  -2,2,.01 &  0.56 & 1.89 x 0.93  &   7.4   &     1.7 &   8.8 &  -6.3 &  100 &  10&  284 \\
Cp &-30 &  -2,2,.01 &  0.56 & 1.88 x 0.93  &   7.4   &     1.7 &   7.5 &  -6.1 &  100 &  10&  284 \\ \hline
\end{tabular}
\raggedright\smallskip
\end{table}
 
\begin{table}
\tablenum{3}
\centering
\caption{Modified CARMA (Ap) configuration using station 20 instead of station 8}
\smallskip
\begin{tabular}{cccccccccccccccc}
\hline
\hline
Config & DEC & HA & Rms & FWHM &Tb rms &  & Sidelobe[\%] &   & Nvis & uvrange \\ \hline
   & degrees & [hrs] & [mJy] & [arcsec] &[mK] &  Rms & Max & Min & [\%] & [m] \\ \hline
A  & 45 &  -2,2,.01 &  0.23 & 0.15 x 0.12 &  295.4   &     1.7 &   8.7 &  -7.2 &  100 & 182& 1885 \\
Ap & 45 &  -2,2,.01 &  0.23 & 0.15 x 0.13 &  272.7   &     1.7 &   7.4 &  -7.2 &  100 & 140& 1885 \\
A  & 30 &  -2,2,.01 &  0.23 & 0.15 x 0.12 &  295.4   &     1.8 &   9.3 &  -7.0 &  100 & 181& 1885 \\
Ap & 30 &  -2,2,.01 &  0.23 & 0.15 x 0.13 &  272.7   &     1.8 &   8.2 &  -7.0 &  100 & 143& 1885 \\
A  & 15 &  -2,2,.01 &  0.24 & 0.15 x 0.13 &  284.6   &     1.9 &  13.3 &  -6.9 &  100 & 163& 1884 \\
Ap & 15 &  -2,2,.01 &  0.24 & 0.15 x 0.13 &  284.6   &     2.0 &  14.1 &  -6.9 &  100 & 127& 1884 \\
A  &  0 &  -2,2,.01 &  0.27 & 0.16 x 0.15 &  260.1   &     2.5 &  29.3 &  -7.1 &  100 & 144& 1833 \\
Ap &  0 &  -2,2,.01 &  0.27 & 0.16 x 0.15 &  260.1   &     2.5 &  33.4 &  -7.1 &  100 & 104& 1833 \\
A  &-15 &  -2,2,.01 &  0.34 & 0.20 x 0.15 &  262.0   &     1.9 &  10.8 &  -6.8 &  100 & 108& 1720 \\
Ap &-15 &  -2,2,.01 &  0.34 & 0.20 x 0.15 &  262.0   &     1.9 &  10.8 &  -6.6 &  100 &  77& 1720 \\
A  &-30 &  -2,2,.01 &  0.56 & 0.32 x 0.15 &  269.7   &     1.8 &   9.0 &  -6.7 &  100 &  62& 1692 \\
Ap &-30 &  -2,2,.01 &  0.56 & 0.33 x 0.15 &  261.6   &     1.7 &   9.2 &  -6.6 &  100 &  53& 1692 \\ \hline
\end{tabular}
\raggedright\smallskip
\end{table}

 
\begin{table}
\tablenum{4}
\centering
\caption{Heterogeneous array where the first 6 antennas are 10m and the last 9 are 6m}
\smallskip
\begin{tabular}{cccccccccccccccc}
\hline
\hline
Config & DEC & HA & Rms & FWHM &Tb rms &  & Sidelobe[\%] &   & Nvis & uvrange \\ \hline
   & degrees & [hrs] & [mJy] & [arcsec] &[mK] &  Rms & Max & Min & [\%] & [m] \\ \hline
A & 30 & -2,2,.01 & 0.18& 0.14 x 0.12 & 247.7   &    2.3 & 13.0 & -9.9 & 100&181&1886 \\
B & 30 & -2,2,.01 & 0.18& 0.31 x 0.23 &  58.4   &    2.1 & 12.1 & -9.0 & 100& 81& 701 \\
C & 30 & -2,2,.01 & 0.18& 1.21 x 1.02 &   3.4   &    3.4 & 15.7 & -9.7 & 100& 48& 273 \\
D & 30 & -2,2,.01 & 0.18& 3.00 x 2.58 &   0.5   &    3.5 & 19.7 & -10.0& 100& 21& 108 \\
E & 30 & -2,2,.01 & 0.18& 5.77 x 5.21 &   0.1   &    2.9 & 16.8 & -9.0 & 100& 10&  50 \\
A &  0 & -2,2,.01 & 0.21& 0.16 x 0.13 & 233.4   &    3.1 & 35.6 & -15.7& 100&144&1834 \\
B &  0 & -2,2,.01 & 0.21& 0.31 x 0.29 &  54.0   &    2.9 & 39.0 & -14.5& 100& 64& 696 \\
C &  0 & -2,2,.01 & 0.21& 1.43 x 1.08 &   3.1   &    4.2 & 48.0 & -10.4& 100& 38& 266 \\
D &  0 & -2,2,.01 & 0.21& 3.60 x 2.70 &   0.5   &    4.3 & 39.7 & -15.3& 100& 17& 105 \\
E &  0 & -2,2,.01 & 0.21& 7.10 x 5.29 &   0.1   &    4.2 & 42.6 & -15.4& 100&  8&  50 \\
A &-30 & -2,2,.01 & 0.43& 0.32 x 0.14 & 221.9   &    2.2 & 12.1 & -10.1& 100&110&1692 \\
B &-30 & -2,2,.01 & 0.43& 0.60 x 0.31 &  53.5   &    1.9 & 12.3 & -8.0 & 100& 30& 688 \\
C &-30 & -2,2,.01 & 0.43& 2.56 x 1.13 &   3.4   &    3.0 & 14.1 & -7.5 & 100& 25& 242 \\
D &-30 & -2,2,.01 & 0.44& 6.37 x 2.74 &   0.6   &    3.2 & 11.3 & -8.2 &  96& 10&  96 \\
E &-30 & -2,2,.01 & 0.73&10.70 x 4.24 &   0.4   &    3.6 & 22.7 & -11.7&  50&  3&  50 \\ \hline
\end{tabular}
\raggedright\smallskip
\end{table}
 
\begin{table}
\tablenum{5}
\centering
\caption{Heterogeneous array where the last 6 antennas are 10m and the first 9 are 6m}
\smallskip
\begin{tabular}{cccccccccccccccc}
\hline
\hline
Config & DEC & HA & Rms & FWHM &Tb rms &  & Sidelobe[\%] &   & Nvis & uvrange \\ \hline
   & degrees & [hrs] & [mJy] & [arcsec] &[mK] &  Rms & Max & Min & [\%] & [m] \\ \hline
A & 30 & -2,2,.01 & 0.18& 0.15 x 0.13 & 213.4   &    2.5 & 10.6 & -11.8 & 100 &181&1886 \\
B & 30 & -2,2,.01 & 0.18& 0.39 x 0.30 &  35.6   &    2.9 & 12.5 & -11.5 & 100 & 81& 701 \\
C & 30 & -2,2,.01 & 0.18& 1.18 x 0.61 &   5.8   &    2.6 & 14.3 & -19.9 & 100 & 48& 273 \\
D & 30 & -2,2,.01 & 0.18& 2.86 x 1.55 &   0.9   &    2.5 & 14.3 & -20.3 & 100 & 21& 108 \\
E & 30 & -2,2,.01 & 0.18& 3.90 x 3.52 &   0.3   &    2.2 & 19.2 & -14.5 & 100 & 10&  50 \\
A &  0 & -2,2,.01 & 0.21& 0.17 x 0.15 & 190.4   &    3.3 & 38.5 & -13.8 & 100 &144&1834 \\
B &  0 & -2,2,.01 & 0.21& 0.40 x 0.37 &  32.8   &    3.8 & 27.9 & -23.8 & 100 & 64& 696 \\
C &  0 & -2,2,.01 & 0.21& 1.17 x 0.76 &   5.5   &    2.8 & 33.8 & -19.8 & 100 & 38& 266 \\
D &  0 & -2,2,.01 & 0.21& 2.82 x 1.92 &   0.9   &    2.8 & 37.6 & -21.7 & 100 & 17& 105 \\
E &  0 & -2,2,.01 & 0.21& 4.42 x 3.90 &   0.3   &    3.1 & 43.4 & -18.4 & 100 &  8&  50 \\
A &-30 & -2,2,.01 & 0.43& 0.35 x 0.16 & 177.5   &    2.4 & 11.6 & -11.4 & 100 &110&1692 \\
B &-30 & -2,2,.01 & 0.43& 0.77 x 0.40 &  32.3   &    2.4 & 12.0 & -8.0  & 100 & 30& 688 \\
C &-30 & -2,2,.01 & 0.43& 1.54 x 1.18 &   5.5   &    1.9 &  9.7 & -15.9 & 100 & 25& 242 \\
D &-30 & -2,2,.01 & 0.44& 3.85 x 2.85 &   0.9   &    1.9 & 11.3 & -16.7 &  95 & 10&  96 \\
E &-30 & -2,2,.01 & 0.55& 7.32 x 3.44 &   0.5   &    2.7 & 16.2 & -14.0 &  43 &  3&  50 \\ \hline
\end{tabular}
\raggedright\smallskip
\end{table}

\end{document}
