
%\input{call_w08_declarations.tex}

\section{News from the Plateau de Bure Interferometer}

\subsection{Weather conditions and observing}

The end of the winter semester as well as the first two months of the
current summer semester have been suffering from quite mediocre  weather
conditions on Plateau de Bure. We moved the array into its B
configuration on March 10 after a two-weeks period in a configuration
intermediate between A and B that still offered the longest baselines
of the A configuration (up to 760m). Two projects requesting the
A-configuration and three projects requesting the B configuration
could not be finished and will be deferred to the upcoming winter
semester.  The C configuration was scheduled after March 29 and the
interferometer was switched back to the most compact configuration D
on May 1st. The spring VLBI session took place from May 8 to 13 with
the interferometer working without technical problems and in
good weather conditions. Since May 14th the array is observing with 5
antennas in D configuration. The current antenna maintenance period is
foreseen to end in October. At the end of this period it is
foreseen to equip the reflector of  antenna 4 with new aluminum panels
replacing the current mix of painted carbon fiber and Media Lario
panels.

As far as A-rated projects are concerned, we still hope to bring many
of these to completion before the end of the summer  semester. B-rated
projects are likely to be observed only if they fall in a favorable
LST range. We remind users of the Plateau de Bure interferometer that
B-rated proposals and A-rated time fillers  which are not started
before the end of the summer period have to be resubmitted.

Global VLBI observations, which include the array in the 3\,mm
phased-array mode, are planned from October 9 to 15.

Investigators who wish to check the status of their project may
consult the interferometer schedule on the Web at
../PDBI/ongoing.html. This page is updated daily.

\signed {Jan Martin WINTERS}

\section{Call for Observing Proposals on the Plateau de Bure Interferometer}

\subsection{Important information}

{\bf Please note that the proposal.sty file and the proposal.tex
template have been changed considerably. We urge proposers to download
the most recent version from our web page\\
../GENERAL/proposal/ . Proposals using older versions of the
style/template files will not be accepted.}

\subsection{Conditions for the next winter session} 

Based on our experience in carrying out configuration changes in 
winter conditions with
limited access to the observatory, we plan to schedule four
configuration changes next winter. We therefore ask investigators to
submit proposals for any of the 4 primary configurations of the six
antenna array.

A preliminary configuration schedule for the winter period is outlined
below. Adjustments to the provisional configuration planning will be
made according to proposal pressure, weather conditions, and other
contingencies. The configuration schedule given below should be taken
as a guideline, in particular when the requested astronomical targets
cannot be observed during the entire winter period (sun avoidance
circle of radius 45$^\circ$).

\vskip 4mm
\begin{center}
\begin{tabular}{cc}
\hline\hline
Conf & {Scheduling Priority Winter 08/09} \\
\hline
C & December\\
A & December -- January\\
B & February -- March\\
C & March -- April\\
D & April -- May\\
\hline
\end{tabular}
\end{center}
\mbox{}\\[1ex]

We strongly encourage observers to submit proposals for the set of
AB configurations that include 730 and 760 meter baselines.  For these
proposals we ask to focus on bright compact sources, possibly at high
declination.

We invite proposers to submit proposals also for observations at
3\,mm. When the atmospheric conditions are not good enough at 1.3\,mm
or at 2\,mm,
3\,mm projects will be observed: in a typical winter, 20-30\% of the
time used for observations is found to be poor at 1.3\,mm, but still
excellent at 3\,mm.

\subsection{Proposal category}
Proposals should be submitted for one of the six categories:
\begin{description}
\item[{\sc 1.3mm:}\/] Proposals that ask for 1.3\,mm data.
3\,mm receivers can be used for pointing and calibration purposes, but cannot
provide any imaging. 
\item[{\sc 2mm:}\/] Proposals that ask for 2\,mm data. 3\,mm receivers can be 
used for pointing and calibration purposes, but cannot
provide any imaging. 
\item[{\sc 3mm:}\/] Proposals that ask for 3\,mm data.
\item[{\sc time filler:}\/] Proposals that have to be considered as
background projects to fill in periods where the atmospheric
conditions do not allow mapping, to fill in gaps in the
scheduling, or even to fill in periods when only a subset of the standard
6-antenna configurations will be available. These proposals will be
carried out on a ``best effort'' basis only.
\item[{\sc special:}\/] Exploratory proposals: proposals whose
scientific interest justifies the attempt to use the PdB array beyond
its guaranteed capabilities. This category includes for example
non-standard frequencies for which the tuning cannot be guaranteed,
non-standard configurations and more generally all non-standard
observations. These proposals will be carried out on a ``best effort''
basis only.
\item[{\sc Large Program:}\/] This category is offered for the first time on 
both IRAM instruments. See Sect. {\it Large Observing Programs}\ref{Large} 
for a detailed explanation.  
\end{description}
The proposal category will have to be specified on the proposal cover
sheet and should be carefully considered by proposers.

\subsection{Configurations of the six-antenna array}

The six-element array can be arranged in the following 
configurations:\\[1ex]
\begin{center}
\begin{tabular}{ccccccc}
\hline\hline                
Conf & \multicolumn{6}{c}{Stations} \\
\hline                        
 A &W27 &E68 &N46 &E04 &E24 &N29 \\
 B &W27 &E23 &N46 &W12 &E12 &N20 \\
 C &W12 &E10 &N17 &W09 &E04 &N11 \\
 D &W08 &E03 &N11 &W05 &N02 &N07 \\
\hline
\end{tabular}
\end{center}

\noindent The general properties of these configurations are:

\begin{itemize}

\item[$\circ$] {\tt A\/} alone is well suited for mapping or size
measurements of very compact, strong sources. It provides a resolution of
$0.8''$ at 100\,GHz, $\sim$0.35$''$ at 230\,GHz.
\item[$\circ$] {\tt B\/} alone yields $\sim$1.2$''$ at 100\,GHz and, in
combination with A provides an angular resolution of $\sim$1.0$''$ at
100\,GHz. It is mainly used for relatively strong sources.
\item[$\circ$] {\tt C\/} provides a fairly complete coverage of the
uv-plane (low sidelobe level) and is well adapted to combine with D
for low angular resolution studies ($\sim$3.5$''$ at 100\,GHz,
$\sim$1.5$''$ at 230\,GHz) and with B for higher resolution
($\sim$1.7$''$ at 100\,GHz, $\sim$0.7$''$ at 230\,GHz). C alone is also
well suited for snapshot and size measurement experiments.
\item[$\circ$] {\tt D\/} alone is best suited for deep integration and
coarse mapping experiments (resolution $\sim 5''$ at 100\,GHz). 
This configuration provides both the
highest sensitivity and the lowest atmospheric phase noise. 
\end{itemize}

\noindent The four configurations can be used in different
combinations to achieve complementary sampling of the uv-plane, and to
improve on angular resolution and sensitivity. Mosaicing is usually
done with D or CD, but the combination BCD can also be requested for
high resolution mosaics. Check the {\sc any}\/ bullet in the proposal
form if the scientific goals can be reached with any of the four
configurations or their subsets. 

Please consult the documentation {\it An Introduction to the IRAM
interferometer} (../IRAMFR/PDB/docu.html) and the IRAM Newsletter
No.~63 (August 4th., 2005, accessible on the web at   {\tt
../IRAMFR/ARN/aug05/aug05.html}) for further details.

\subsection{Receivers}

All antennas are equipped with dual polarization
receivers for the 3\,mm, 2\,mm, and 1.3\,mm atmospheric windows.  The
frequency range is 80\,GHz to 116\,GHz for the 3\,mm band, 129\,GHz to
174\,GHz for the 2\,mm band, and 201 to 267\,GHz for the 1.3\,mm band.

\vskip 4mm 
\begin{center}
\begin{tabular}{lccc}
\hline
                   & Band 1  & Band 2       & Band 3   \\
\hline
 RF range$^*$      & 80--116  & 129--174 & 201--267 \\
 $\rm T_{rec}$ LSB &  40--55  & 30--50   & 40--60   \\
 $\rm T_{rec}$ USB &  40--55  & 40--80   & 50--70   \\
 $\rm G_{im}$/[dB] &  -10     & -12 ... -10 &-12 ... -8 \\
 RF LSB            &  80--104 & 129--168 & 201--267 \\
 RF USB            & 104--116 & 147--174 &          \\
\hline
\end{tabular}
\end{center}
\mbox {} \hskip 2mm $^*$ center of the 4-8\,GHz IF band
\vskip 4mm 

Each band of the receivers is dual-polarization  with the two RF
channels of one band observing at the same frequency.  The different
bands are not co-aligned in the focal plane (and therefore on the
sky).  Due to the pointing offsets between the different frequency
bands, only one band can be observed at any time. One of the two other
bands is in stand-by mode (power on and local oscillator phase-locked)
and is available, e.g., for pointing. Time-shared observations between
different RF bands are presently being tested. Please contact the
Interferometer Science Operations Group (sog@iram.fr) to discuss the
feasibility in case you are interested to use this mode.

The mixers are single-sideband, backshort-tuned; they will usually be
tuned LSB,  except for the upper part of the frequency range at 3\,mm
and 2\,mm where the mixers will be tuned USB.

The typical image rejection is 10\,dB. Each IF channel is 4~GHz wide
(4-8~GHz).  The two 4~GHz wide IF-channels (one per polarization)  can
be processed only partially by the existing correlator.  A dedicated
IF processor converts selected 1~GHz wide slices of the 4-8~GHz first
IFs down to 0.1-1.1~GHz, the input range of the existing correlator.
Further details are given in the section describing the correlator
setup and the IF processor.

\subsection{Signal to Noise}

The rms noise can be computed from
\begin{equation}
 \sigma = \frac{J_{\rm pK} T_{\rm sys}} {\eta \sqrt{N_{\rm a} (N_{\rm a}-1) 
N_{\rm c} T_{\rm ON} B}} \frac{1}{\sqrt{N_{\rm pol}}}
\end{equation}
where
\begin{itemize}
\item $J_{\rm pK}$\ is the conversion factor from Kelvin to Jansky (22
Jy/K at 3\,mm, 29 Jy/K at 2\,mm, and 35 Jy/K at 1.3\,mm)
\item $T_{\rm sys}$ is the system temperature ($T_{\rm sys}$ = 100\,K
below 110\,GHz,  170\,K at 115\,GHz, 150\,K at 150\,GHz, and 200\,K at 
230\,GHz for sources at
$\delta \ge 20^\circ$ and for typical winter conditions).
\item $\eta$ is an efficiency factor due to atmospheric phase noise   
and instrumental phase jitter
(0.9 at 3\,mm, 0.85 at 2\,mm, and 0.8 at 1.3\,mm) in typical winter conditions.
\item $N_{\rm a}$ is the number of antennas (6), and $N_{\rm c}$ 
is the number of
configurations: 1 for D, 2 for CD, and so on.
\item $T_{\rm ON}$ is the on-source integration time per configuration
in seconds (2 to 8 hours, depending on source declination). Because of
various calibration observations the total observing time is typically
1.6 $T_{\rm ON}$.
\item $B$ is the spectral bandwidth in Hz (up to 2\,GHz for continuum, 
40\,kHz to 2.5\,MHz for spectral line, according to the spectral correlator
setup)
\item $N_{\rm pol}$ is the number of polarizations: 1 for single polarization 
and 2 for dual polarization (see section {\it Correlator} for details).
\end{itemize}

Investigators have to specify the one sigma noise level which is
necessary to achieve each individual goal of a proposal, and
particularly for projects aiming at deep integrations.

\subsection{Coordinates and Velocities}

For best position accuracy, source coordinates must be in the J2000.0
system.

Please do not forget to specify LSR velocities for the sources. For
pure continuum projects, the ``special'' velocity {\tt NULL} (no
Doppler tracking) can be used.

\subsection{Correlator}

\subsubsection{IF processor} 

At any given time, only one frequency band can be observed, but with the two
polarizations available. Each polarization delivers a 4 GHz bandwidth 
(from IF=4 to 8~GHz). The two 4-GHz bandwidths coincide in the sky
frequency scale. The current correlator accepts
as input two signals of 1~GHz bandwidth, that must be selected within
the 4~GHz delivered by the receiver. In practice, the new IF
processor splits the two input 4--8~GHz bands in four 1~GHz
``quarters'', labeled {\em Q1...Q4}. Two of these quarters must be
selected as correlator inputs. The system allows the following
choices:
\begin{itemize}
\item first  correlator entry can only be Q1 HOR, or Q2 HOR, 
or Q3 VER, or Q4 VER
\item second correlator entry can only be Q1 VER, or Q2 VER, 
or Q3 HOR, or Q4 HOR
\end{itemize}
where HOR and VER refer to the two polarizations:
\begin{flushleft}
\begin{center}
\begin{tabular}{l|cccc}
\hline\noalign{\smallskip}
Quarter  & Q1 & Q2 & Q3 & Q4 \\
IF1 [GHz]& 4.2-5.2 & 5-6 & 6-7 & 6.8-7.8\\
\noalign{\smallskip}\hline\noalign{\smallskip}
input 1 & HOR  & HOR  & VER  & VER  \\
input 2 & VER  & VER  & HOR  & HOR  \\
\noalign{\smallskip}\hline
\end{tabular}
\end{center}
\end{flushleft}
\bigskip

{\em How to observe two polarizations?} To observe simultaneously two
polarizations at the same sky frequency, one must select the same quarter 
(Q1 or Q2 or Q3 or Q4)
for the two correlator entries. This will necessarily result in each
entry seeing a different polarization. The system thus give access
to 1~GHz $\times$ 2 polarizations. \\

{\em How to use the full 2~GHz bandwidth?} If two different quarters
are selected (any combination is possible), a bandwidth of 2~GHz can
be analyzed by the correlator. But only one polarization per quarter
is available in that case; this may or may not be the same
polarization for the two chunks of 1~GHz. \\

{\em Is there any overlap between the four quarters?} In fact, the
four available quarters are 1~GHz wide each, but with a small overlap
between some of them: Q1 is 4.2 to 5.2~GHz, Q2 is 5 to 6~GHz, Q3 is
6 to 7~GHz, and Q4 is 6.8 to 7.8~GHz. This results from the combination
of filters and LOs used in the IF processor. \\

{\em Is the 2~GHz bandwidth necessarily continuous?} No: any combination
of two quarters can be selected. Adjacent quarters will result in a
continuous 2~GHz band. Non-adjacent quarters will result in two
independent 1~GHz bands.\\

{\em Where is the selected sky frequency in the IF band?} It would be
natural to tune the receivers such that the selected sky frequency
corresponds to the middle of the IF bandwidth, i.e.\ 6.0~GHz. However,
this corresponds to the limit between Q2 and Q3. It is therefore
highly recommended to center a line at the center of a quarter (see
Section ``ASTRO'' below). In all three bands, 3\,mm, 2\,mm, and 1.3\,mm 
the receivers offer best
performance in terms of receiver noise and sideband rejection in Q3
(i.e. the line should be centered at an IF1 frequency of 6500 MHz).%\\

\subsubsection{Spectral units of the correlator} 

The correlator has 8 independent units, which can be placed anywhere
in the 100--1100~MHz band (1~GHz bandwidth). 7 different modes of
configuration are available, characterized in the following by couples
of total bandwidth/number of channels. In the 3 DSB modes (320MHz/128,
160MHz/256, 80MHz/512 -- see Table) the two central channels may be
perturbed by the Gibbs phenomenon if the observed source has a strong
continuum. When using these modes, it is recommended to avoid
centering the most important part of the lines in the middle of the
band of the correlator unit. In the remaining SSB modes (160MHz/128,
80MHz/256, 40MHz/512, 20MHz/512) the two central channels are not
affected by the Gibbs phenomenon and, therefore, these modes may be
preferable for some spectroscopic studies.

\vskip 4mm \begin{center}
\begin{tabular}{crrc}
\hline
\hline
 Spacing & Channels & Bandwidth  & Mode \\
 \multicolumn{1}{c}{(MHz)} & & \multicolumn{1}{c}{(MHz)} & \\
\hline
 0.039 &$ 1 \times 512$ &  20 & SSB \\
 0.078 &$ 1 \times 512$ &  40 & SSB \\
 0.156 &$ 2 \times 256$ &  80 & DSB \\
 0.312 &$ 1 \times 256$ &  80 & SSB \\
 0.625 &$ 2 \times 128$ & 160 & DSB \\
 1.250 &$ 1 \times 128$ & 160 & SSB \\
 2.500 &$ 2 \times  64$ & 320 & DSB \\
\hline
\end{tabular}
\end{center}
\vskip 3mm
\noindent Note that 5\% of the passband is lost at the end of each
subband.  The 8 units can be independently connected to the first or
the second correlator entry, as selected by the IF processor (see
above). Please note that the center frequency is expressed in the 
frequency range seen by the correlator, i.e.\ 100
to 1100~MHz. The correspondence to the sky frequency depends on
the parts of the 4~GHz bandwidth which have been selected as correlator 
inputs. \\

\subsubsection{ASTRO}

The software ASTRO can be used to simulate the 
receiver/correlator configuration. Astronomers are urged to
download the most recent version of GILDAS  at {\tt ../IRAMFR/GILDAS/} 
to prepare their proposals.\\

The previous {\tt LINE} command has been replaced by several new commands
(see internal help; the following description applies to the current
receiver system). The behavior of the {\tt LINE} command can be
changed by the {\tt SET PDBI 1995|2000|2006} command, that selects the
PdBI frontend/backend status corresponding to years 1995 (old
receivers, 500 MHz bandwidth), 2000 (580 MHz bandwidth), 2006 (new
receivers and new IF processor, 1\,GHz bandwidth). Default is 2006:
\begin{itemize}
\item {\tt LINE}: receiver tuning
\item {\tt NARROW}: selection of the narrow-band correlator inputs
\item {\tt SPECTRAL}: spectral correlator unit tuning
\item {\tt PLOT}: control of the plot parameters. 
\end{itemize}
A typical session would be:

\begin{verbatim}
   ! choice of receiver tuning
   line xyz 230 lsb low 6500

   ! choice of the correlator windows
   narrow Q3 Q3             

   ! correlator unit #1, on entry 1
   spectral 1  20 520 /narrow 1   

   ! correlator unit #2, on entry 1
   spectral 2 320 260 /narrow 1   

   ! correlator unit #3, on entry 2
   spectral 3  40 666 /narrow 2   
   ...
\end{verbatim}

\vskip 4mm
\subsection{Sun Avoidance}

For safety reasons, a sun avoidance limit is enforced at 45 degrees
from the sun. Please take this into account for your target sources.

\subsection{Mosaics}
The PdBI has mosaicing capabilities, but the pointing accuracy may be
a limiting factor at the highest frequencies. Please contact the
Science Operations Group (sog@iram.fr) in case of doubts.

\subsection{Data reduction}
Proposers should be aware of constraints for data reduction:
\begin{itemize}
\item[$\circ$] In view of the new receiver system, we recommend that you
reduce your data in Grenoble. Proposers will not come for the
observations, but will have to come for the data reduction.  For the time
being, remote data reduction will only be offered in exceptional cases. 
Please contact your local
contact if you're interested in this possibility.
%Remote data reduction is possible, especially for experienced
%users of the Plateau de Bure Interferometer. Please contact your local
%contact if you're interested in this possibility.
\item[$\circ$] We keep the data reduction schedule very flexible, but wish to
avoid the presence of more than 2 groups at the same time in
Grenoble. Data reduction will be carried out on dedicated computers at
IRAM. Please contact us in advance.
\item[$\circ$] In certain cases, proposers may have a look at the
uv-tables as the observations progress. If necessary, and upon
request, more information can be provided. Please contact your local contact 
or PdBI's Science
Operations Group (sog@iram.fr) if you are interested in this.
\item[$\circ$] CLIC evolves to cope with upgrades of the PdBI
array. The newer versions are downward compatible with the previous
releases. Observers who wish to finish data reduction at their
home institute should obtain the most recent version of CLIC. Because
differences between CLIC versions may potentially result in imaging
errors if new data are reduced with an old package, we advise
observers having a copy of CLIC to take special care in maintaining it
up-to-date.  The recent upgrades of CLIC implied many
modifications for which backward compatibility with old PdBI receiver data has
not yet been fully checked. To calibrate data obtained with the ``old''
receiver system (up to September 2006), 
one has to use the January 2007 version of CLIC.
\end{itemize}

\subsection{Local Contact}
A local contact will be assigned to every A or B rated proposal which
does not involve an in-house collaborator. He/she will assist you in
the preparation of the observing procedures and provide help to reduce
the data. Assistance is also provided before a deadline to help
newcomers in the preparation of a proposal. Depending upon the
program complexity, IRAM may require an in-house collaborator
instead of the normal local contact.

\subsection{Technical pre-screening}
All proposals will be reviewed for technical feasibility in parallel
to being sent to the members of the program committee. Please help
in this task by submitting technically precise proposals. Note that
your proposal must be complete and exact: the source position and velocity,
as well as the requested frequency setup must be correctly given.

\subsection{Non-standard observations}
If you plan to execute a non-standard program, please contact the
Interferometer Science Operations Group (sog@iram.fr) to discuss the
feasibility.

\subsection{Documentation}

The documentation for the IRAM Plateau de Bure Interferometer includes
documents of general interest to potential users, and more specialized
documents intended for observers on the site (IRAM on-duty
astronomers, operators, or observers with non-standard programs). All
documents can be retrieved on the Internet at {\tt
../IRAMFR/PDB/docu.html}.
Note however, that not all the
documentation on  the web has already been updated with respect to the
current receivers. All information presently available on the
current receiver system is given in the {\it Introduction to
the IRAM Plateau de Bure Interferometer} at {\tt
../IRAMFR/GILDAS/doc/html/pdbi-intro-html} and in this call for
proposals.\\

\renewcommand{\finally}{Finally, we would like to stress again the
importance of the quality of the observing proposal.  The IRAM
interferometer is a powerful, but complex instrument, and proposal
preparation requires special care. Information is available in this 
call and at {\tt ../IRAMFR/PDB/docu.html}. The IRAM staff can help
in case of doubts if contacted well before the deadline. Note that the
proposal should not only justify the scientific interest, but also the
need for the Plateau de Bure Interferometer.}

\begin{latexonly}
\fullbox{3mm}{\finally}
\end{latexonly}
\begin{htmlonly}
{\bf \finally}
\end{htmlonly}

\signed {Jan Martin WINTERS}


%\end{document}

