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\title{An Introduction to the IRAM NOEMA interferometer}
\author{M. Krips\\
  (update 2019)\\
  \mbox{}\\
  Past contributors: J.M. Winters, S. K\"onig, R. Neri, S. Guilloteau,
  R. Lucas} \date{August 2, 2019 \\ Version 6.0--00} \makeindex{}

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\begin{document}

\def\degr{\hbox{$^\circ$}}
\def\arcmin{\hbox{$^\prime$}}
\def\arcsec{\hbox{$^{\prime\prime}$}}

\maketitle{}

\begin{center}
  Institut de Radio Astronomie Millim\'etrique\\
  300 Rue de la Piscine\\
  F-38406 Saint Martin d'H\`eres
\end{center}

\justify{\noindent This document introduces IRAM's interferometer
  called NOEMA to potential users. It contains general information
  about its capabilities and performance.} \\

\begin{rawhtml}
  Note: this is the on-line version of the "Introduction to NOEMA" 
  A <A HREF="../../pdf/noema-intro.pdf"> PDF version</A> is also available.
\end{rawhtml}

\noindent Related information is available in:
\begin{latexonly}
\begin{itemize}\itemsep -1mm
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/gildas-intro-html/gildas-intro.html}{\tt GILDAS: Grenoble Image and Line Data Analysis Software}}
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/astro-html/astro.html}{\tt ASTRO: Astronomical Software To pRepare Observations}}
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/clic-html/clic.html}{\tt CLIC: Continuum and Line Interferometric Calibration}}
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/pdbi-cookbook-html/pdbi-cookbook.html}{\tt NOEMA: Calibration Cookbook}}
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/map-html/map.html}{\tt NOEMA: Mapping Cookbook}}
\end{itemize}
\end{latexonly}

\begin{rawhtml}
  <UL>
  <LI> <A HREF="../gildas-intro-html/gildas-intro.html"> GILDAS:</A> Grenoble
  Image and Line Data Analysis Software
  <LI> <A HREF="../astro-html/astro.html"> ASTRO:</A> A Software to pRepare
  Observations 
  <LI> <A HREF="../clic-html/clic.html"> CLIC:
  <LI> NOEMA:
  <A HREF="../pdbi-cookbook-html/pdbi-cookbook.html"> Calibration CookBook</A>
  <LI> NOEMA:
  <A HREF="../map-html/map.html"> Mapping CookBook</A>
\end{rawhtml}

\noindent
Revision 6.0: NOEMA Antenna 9,10, PolyFiX\\
Revision 5.1: NOEMA Antenna 8, NOEMA 2SB receivers (SSB mode)\\
Revision 5.0: NOEMA Antenna 7\\
Revision 4.2: Band 4\\
Revision 4.1: WideX\\
Revision 4.0: NGR system and extended array configurations\\

\newpage
\tableofcontents

\newpage
\section{Description} \index{NOEMA interferometer}

The NOrthern Extended Millimeter Array (NOEMA) is located in the South
of the French Alps, near St Etienne en D\'evoluy in the  D\'epartment
Hautes Alpes. The interferometer's altitude is 2560\,m at the
intersection of the Azimuth and Elevation axes of the  telescopes, and
its longitude and latitude are 05:54:28.5 E and 44:38:02.0 N at the
array phase center. The interferometer currently  comprises

\begin{itemize}
\item ten antennas of 15\,m diameter,

\item baselines ranging up to 760\,m

\item a high-performance wide-band correlator named
  \textit{PolyFiX}\index{PolyFiX}

\item dual polarization receivers\index{receivers} covering the 3\,mm,
  2\,mm and 1.3\,mm wavelength bands

\end{itemize}

\noindent The ten antennas of the interferometer can be positioned on
32 stations layed out along a ``T'' shaped track\index{tracks} (see
Figure\,\ref{pdblayout}). The north-south arm is 368\,m long, and the
east-west oriented arm extends 216\,m west and 544\,m east of the
intersection. The angle between the arms is 75\degr. The station names
are taken from the arm orientation and a two digit code indicating the
distance from the track intersection (station W00) in 8\,m units. 

Until 2021, two more antennas will join NOEMA and the baselines will
be extended up to almost 1700~m on the East-West arms, bringing NOEMA
close to its full capabilities.

Each antenna \index{antenna} is a 15\,m diameter Cassegrain telescope
constructed largely of carbon fiber. The primary mirrors have a
surface accuracy below 50\,$\mu$m rms. The antenna mounts incorporate
self propelled transporters for moving the antennas along the tracks
between stations. 

The antennas are equipped with three receiver bands, observing in dual
polarization and two sidebands in the 3\,mm, 2\,mm, and 1.3\,mm
%, and  0.8\,mm
atmospheric windows, respectively. The 3\,mm receiver band covers sky
frequencies between $\sim$71 and 119\,GHz, the 2\,mm receiver band
covers sky frequencies between $\sim$127 to 182\,GHz, and the 1.3\,mm
receiver band covers sky frequencies between $\sim$197 and 276\,GHz.
% , and the 0.8\,mm receiver band covers the 277 to 371\,GHz frequency
% range.
Typical receiver noise temperatures range from 25\,K to 45\,K, at
3\,mm, from 35\,K to 55\,K at 2\,mm, and from 40\,K to 70\,K at
1.3\,mm.
%, and the noise temperatures at 0.8\,mm are typically 30-50\,K. 
More details about the receivers are given in
Sect.\,\ref{receiversec}, a comprehensive summary can be found in
Table\,\ref{receivertab}.

The dual polar, 2SB receivers deliver four IF outputs (one per
polarization and one per sideband), each 7.744\,GHz wide. These are
transmitted by optical fibers to the central building. An IF processor
further splits each of the four IF outputs into two 3.872~GHz wide
basebands per sideband and polarisation which are called outer and
inner basebands.  These eight basebands are then fed into the
correlator (see also Figure~\ref{fig1}).

The wide-band correlator PolyFiX\index{PolyFiX}, in its low spectral
resolution mode with a 2~MHz channel spacing, can process a total
instantaneous bandwidth of $\sim$31GHz for up to twelve antennas (see
Sect.\,\ref{correlsec} for more details). The 31~GHz are thereby split
up over the two sidebands and polarisations. In addition, a high
spectral resolution mode with a channel spacing of 62.5~kHz is also
available for a large number of spectral windows that can be placed in
both sidebands and polarisations. Further modes will become available
in the future.


A 64-bit Linux computer and several embedded processors control the
interferometer and acquire the data. The user interface, \obs\ , is a
variant of PaKo, familiar to most users of the IRAM 30\,m telescope.

Each interferometer configuration,\index{configuration} i.e. the
placement of the 10 antennas on predefined stations within the array,
provides 45 baselines simultaneously.  For each configuration, a list
of projects is provided to the on-site operator and the astronomer on
duty, allowing for a flexible scheduling of the observations well
adapted to the actual meteorological conditions. Depending on the
weather and on the season, configurations are changed every two to six
months, so a project that requires two configurations will on average
take about four months to be completed.

\begin{figure}[t]
  \includegraphics[width=\textwidth]{noema-intro-uv-cover}
  \caption{Example of uv-coverage (left) and interferometer station layout 
(right) for the 10D configuration, as produced by the 
   \astro\  \index{ASTRO} {\tt UV\_TRACK} command. 
% astro \index{ASTRO} {\tt UV\_TRACK} command.  
   The shaded circle at the center of the uv-plane shows the short
   spacing region that cannot be observed with the array.}
\label{pdblayout}
\end{figure}

\section{Capabilities}

\subsection{Spatial Resolution}

Three primary 10 antenna configurations (see Table~\ref{configs}) are
available that can be combined to produce maps with different angular
resolution. All three configurations are usually scheduled during the
course of a year (see Table~\ref{configs}). During the summer period
(May until September) each antenna undergoes a thorough maintenance
and the interferometer is operated in a 9 antenna D configuration.\\

\begin{table}
  \caption{Configurations of the ten-antenna array \index{configuration}}
\label{configs}
\begin{center}
\begin{tabular}{|r|c|c|c|c|c|c|c|c|c|c|}
%\begin{tabular}{|r|c|c|c|c|c|c|c|c|c|c|c|}
\hline
Name & \multicolumn{10}{c|}{Stations}  \\
\hline
 10A  & W27 & W23 & W08 & E68 & E24 & E16 & E03 & N46 & N29 & N20 \\
 10C  & W23 & W20 & W09 & E23 & E18 & E10 & E03 & N20 & N17 & N11 \\
 10D  & W12 & W08 & W05 & E10 & E04 & N17 & N13 & N09 & N05 & N02 \\ 
  9D  & W12 & W09 & W05 & E10 & E04 & --  & N13 & N09 & N05 & N02 \\
% 11D  & W20 & W12 & W09 & W05 & E16 & E12 & E03 & N17 & N13 & N09 & N02 \\
\hline
\end{tabular}
\end{center}
\end{table}

\noindent The general properties of these configurations (numbers refer
to a source at 20$^\circ$ declination) are:

\begin{itemize}

\item {\bf D} -- the compact configuration with just the D array for
  maximum sensitivity.\index{sensitivity} This configuration is best
  suited for detection experiments and coarse mapping (resolution
  $\sim 3.9''$ at 100\,GHz and $\sim 1.7''$ at 230\,GHz). This
  configuration provides the lowest phase noise and highest
  sensitivity.
\item {\bf C} -- the intermediate configuration 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$2.6$''$ at 100\,GHz, $\sim$1.1$''$ at 230\,GHz) and with A
  for higher resolution ($\sim$1.4$''$ at 100\,GHz, $\sim$0.6$''$ at
  230\,GHz).  C alone ($\sim$2$''$ at 100\,GHz, $\sim$0.9$''$ at
  230\,GHz) is also well suited for snapshot and size measurements,
  and for detection experiments at low source declination.
\item {\bf A} -- the most extended configuration alone is well suited
  for mapping or size measurements of compact, strong sources. It
  provides a resolution of $1.0''$ at 100\,GHz, $\sim$0.4$''$ at
  230\,GHz.
\end{itemize}

\noindent The three configurations \index{configuration} can be used
in different combinations to achieve complementary sampling of the
uv-plane, and to improve on angular resolution and
sensitivity.\index{sensitivity} The combinations AC, ACD, and CD are
well suited for all declinations above 0\degr\,.
%(see Tables\,\ref{beamCD} to \ref{beamACD}). 
For lower source declinations, the beam becomes increasingly
elliptical. Sources lower than -25\degr\, declination cannot
reasonably be observed from Plateau de Bure. Mosaicing is usually done
with D or CD, but the combination ACD can also be requested for high
resolution mosaics.

The antenna half-power beam size is 50\arcsec\ at 100\,GHz and the
shortest possible antenna spacing is 24\,m to avoid collisions between
two antennas. Even taking into account projection effects that shorten
the effective baseline, sources larger than about 15\arcsec\ are
already heavily resolved at 100\,GHz. In these cases, additional
short-spacing observations should be acquired by observing a raster-
or OTF- (On-The-Fly) map using the IRAM 30~m telescope\footnote{see
  also the
  \href{http://www.iram-institute.org/medias/uploads/IRAM_memo_2008-2-short-spacings.pdf}{\tt
    IRAM memo 2008-2}: {\it Single-dish observation and processing to
    produce the short-spacing \hspace*{4mm} information for a
    millimeter interferometer} by N.J. Rodr{\'i}guez-Fern{\'a}ndez, J.
  Pety \& F. Gueth}. The short-spacing information can then easily be
added to the uv-tables obtained from the interferometer by means of
the GILDAS\index{GILDAS} \mapping\ \index{MAPPING} software.
%the GILDAS\index{GILDAS} mapping \index{MAPPING} software 
(see also Section\ref{shortspace}).



%Tables\,\ref{beamD}-\ref{beamA} give a summary of possible beam
%sizes\index{beam sizes} at various observing frequencies in different
%configurations using natural weighting. The numbers were obtained
%assuming observations of the target source from 4~hours before to
%4~hours after transit down to elevations above 20 degrees. Typical
%uv-coverages and resulting beam shapes for the eight-element array are
%shown in Figs.\,\ref{fig:8cd} (D and CD) and \ref{fig:8ac} (AC and A).


\newpage

\subsection{Receivers}\label{receiversec}\index{receivers}

All NOEMA antennas are equipped with 2SB receivers, providing low
noise performance and excellent long-term stability. The receivers
provide two orthogonal linear polarizations in all three bands. Each
of the two polarizations delivers a bandwidth of 7.744\,GHz in the
lower sideband (LSB) and upper sideband (USB) simultaneously. The sky
frequency ranges that can be covered in each band and further
characteristics are given in Table~\ref{receivertab}.  Receiver tuning
will preferentially be done on a fixed frequency grid\index{Frequency
  grid} of 500\,MHz step width, on which the receiver performance is
optimized (see Sect.~\ref{astrosec} for more details).



\begin{table}[t]
\caption{Receiver specifications. }
\label{receivertab}
\begin{center}
\begin{tabular}{|lccc|}
\hline
                      & Band 1    & Band 2   & Band 3   \\
\hline
$\rm F_{LO1}$  range/[GHz]$^\star$ & 82.000--108.256 & 138.616--171.256 &  207.744--264.384 \\ 
$\rm F_{sky}$ range/[GHz]$^\star$  & 70.384--119.872 & 127.000--182.872 &  196.128--276.000 \\
 $\rm T_{rec}$/[K]$^{\star\star}$     &  25--45    & 35--55   & 40--70    \\
% $\rm T_{rec}$/[K] USB &  25--35    & 30--50   & 30--60    \\
$\rm G_{im}$/[dB]     & -15-...-10    & -15...-10 &-15 ... -10 \\
\hline
\end{tabular}
\end{center}
\justify{\footnotesize $^\star$ Guaranteed LO1 frequency
%\footnotesize $^\star$ Guaranteed LO1 frequency
  ranges per offered band. The LO1 frequency is the center frequency
  between the USB and LSB that can both be simultaneously observed in
  one tuning (see Fig~\ref{fig1}). The center frequency of the USB
  (LSB) is separated by $+$($-$)7.744~GHz from the LO1 frequency. With
  an effective width of 7.744~GHz per sideband the lowest and highest
  sky frequencies that can be covered per tuning are therefore $\rm
  F_{sky}$=$\rm F_{LO1}\pm$11.616~GHz. The lowest and highest LO1
  frequencies per band define the $\rm
  F_{sky}$ ranges that are currently guaranteed. \\
  $^{\star\star}$ for LSB and USB. }
\end{table}

\subsection{The Wideband Correlator
  PolyFiX}\label{correlsec}\index{correlators}

The wide-band correlator PolyFiX\index{PolyFiX} can process a total
instantaneous bandwidth of $\sim$ 31\,GHz
%(= 4 $\times$ 7.744\,GHz)
for up to twelve antennas that is split into two polarisations in each
of the two available sidebands (the {\it upper} and {\it lower}
sideband). The centers of the two 7.744~GHz wide sidebands are
separated by 15.488~GHz.  Each sideband is composed of two adjacent
{\it basebands} of $\sim$3.9\,GHz width, called {\it inner} and {\it
  outer} baseband (see Fig.~1). In total, there are thus eight
basebands which are fed into the correlator. The channel spacing is
2\,MHz\footnote{due to default signal apodization with a sinc$^2$
  function, the effective spectral resolution is 1.772 times the
  channel spacing} throughout the 15.488\,GHz effective bandwidth per
polarization. Additionally, up to sixteen high-resolution {\it chunks}
can be selected in each of the eight basebands (i.e.\ up to 128 chunks
in total). Each of these has a width of 64\,MHz and, in the current
implementation step of PolyFiX, a fixed channel spacing of
62.5\,kHz. A number of contiguous chunks defines one spectral window
(SPW).

Please note that there is a ``non-exploitable, 20~MHz wide frequency
area'' ($\equiv$ LO2 zone) around the center of each sideband, i.e.,
in between the inner and outer basebands. Due to the filter response
of the correlator, the noise level is also increased by up to a factor
of two within a width of $\pm$50~MHz around the center in each
sideband. Important lines should therefore not be placed in this
region (see also pages 19 and 20 in \htmladdnormallink{\tt this
  PolyFiX
  tutorial}{http://www.iram.fr/~gildas/demos/astro/demo-astro-noema.pdf}).

Subsection\ref{astrosec} explains how to configure the correlator
using the \gildas\ package \astro.

\begin{figure*}[!t]
  \centering   
  \includegraphics[width=\hsize]{basebands}
  \caption{Basebands fed to the correlator}
  \label{fig1}
\end{figure*}






\subsection{Sensitivity}


The 1\,sigma point source sensitivity \index{sensitivity} (in Jy) can
be derived with:

\begin{equation}
\sigma = \frac{J_{\rm pK} T_{\rm sys}}{\eta \sqrt{N_a (N_a-1) T_{\rm ON} B}} \frac{1}{\sqrt{N_{\rm pol}}}
\end{equation}

\noindent where
\begin{itemize}

\item $J_{pK}$ is the antenna efficiency \index{antenna efficiency}
  (Jy\,K$^{-1}$) i.e. $2k/(\eta _a A)$ with $\eta _{a}$ the aperture
  efficiency, $A$ the antenna collecting area, and $k$ the Boltzmann
  constant.

\item $\eta$ is an additional efficiency factor due to atmospheric
  decorrelation. The short and long term atmospheric phase
  fluctuations depend on the baseline length, atmospheric stability
  and frequency.

\item $T_{\rm sys}$ is the system temperature \index{system
    temperature} outside the atmosphere, i.e. corrected for
  atmospheric transmission.

\item $N_{\rm a}$ is the number of antennas

\item $T_{\rm ON}$ is the on-source integration time in
  seconds. Because of various calibration overheads, the total
  observing time is typically at least 1.6 $T_{\rm ON}$ .

\item $B$ is the noise equivalent bandwidth of the correlator in Hz,
  equal to $\sim$1.8 times the channel separation; the effective
  channel width for standard apodization (using a Hanning time-lag
  window) is 1.772 times the channel separation.

\item $N_{\rm pol}$ is the number of polarizations: 1 for single
polarization and 2 for dual polarization

\end{itemize}


\noindent To provide the most realistic and up-to-date estimates of
the sensitivity of NOEMA, NOEMA provides sophisticated sensitivity
calculators via \htmladdnormallink{\tt PMS}{http://pms.iram.fr} (see
Section~\ref{PMS}) and via the \gildas\ software package \astro\ (please
use
%via the gildas software package astro (please use 
the most recent \htmladdnormallink{\tt
  GILDAS}{http://www.iram.fr/~gildas/dist/index.html} version when
preparing your proposals). Both softwares use the same calculations,
based on equation (1) given above, and are regularly updated with the
latest NOEMA characteristics.

The point source sensitivity obviously depends on the observing
frequency and hence a so called representative frequency has to be
choosen in order to calculate the sensitivity in \astro\ and
\htmladdnormallink{\tt PMS}{http://pms.iram.fr}.  In
\htmladdnormallink{\tt PMS}{http://pms.iram.fr}, the representative
frequency has to be within the frequency range and for high spectral
resolution projects within one of the high resolution spectral windows
that are selected in the respective technical sheet. The
representative frequency does not have to be identical to the actual
tuning frequency.  Please note, that due to the large bandwidth and
the dual-sideband mode, the noise can vary significantly with
frequency in the available frequency range. Especially, if one of the
sidebands is close to a receiver band edge, significant differences in
the noise can occur within and between the sidebands. This should be
taken into consideration when setting the re\-presentative frequency
for each tuning. Please note that \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} and \astro\ take into account variations of
the noise across the entire 15.488~GHz bandwidth to calculate the {\it
  continuum} sensitivity. Both tools also account for the declination
of the source to estimate the rms noise levels. Longer telescope times
are needed for sources at low declinations ($\delta < -10^\circ$) to
achieve the same point-source sensitivity.





\section{Proposal Preparation}

To exploit the full capabilities of NOEMA, proposals must be written
with special care. It is of the utmost importance to  provide the
following parameters:

\begin{itemize}
\item A source list with accurate coordinates, velocities/redshifts
\item Observing frequencies
\item A source list with velocities and line width for spectral line
observations
\item Required spatial and spectral resolution, and estimate of
required sensitivity
\item For special cases: Required accuracy of the bandpass calibration
(e.g., a weak line on a strong continuum, high precision relative
astrometry)
\item Dates to be avoided during scheduling, e.g., because of sun avoidance
(a circle of 32 degree radius), phase stability requirements (daytime
is often difficult in summer), or other reasons (specify)
\item Any other stringent constraint (e.g. coordinated or triggered
  observations); please note that we currently guarantee a trigger
  response of three days
      

\end{itemize}

\noindent {\bf This information is absolutely required to decide about
  the feasibility of the program, a prerequisite before the program
  committee can consider the proposal}.




\subsection{The Proposal Management System (PMS)}
\label{PMS}

Proposals must be submitted \index{proposal submission} through the
Proposal Management System (PMS) \index{PMS} at URL:
\href{http://pms.iram.fr}{\tt http://pms.iram.fr}.

Proposal editors will have to create a \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} account to be able to login and
prepare/submit their proposals. To do so, it is sufficient to click on
the URL above and to follow the instructions on-screen that guide the
proposal editor through the submission process.  The submission
procedure consists in filling in an on-line form with the details of
the requested observations (source coordinates, receiver and
correlator setups, array configuration, etc.), and to upload a single
file in pdf format containing the scientific and technical
justification. A LATEX template is provided from the
\htmladdnormallink{\tt PMS}{http://pms.iram.fr} submission page. This
file may be customized, but proposers should respect the following
requirements: (1) a normal proposal may contain up to two pages of
text describing the scientific aims and technical description (4 pages
for a Large Program, see below) (2) you may add up to two pages of
figures, tables, and references (but don't mix text with figures,
tables, and references!), and (3) the font size must be 11pt or
larger.

For a proposal to be complete, \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} requires that all authors validate their
identity (e-mail and affiliation) and their participation to the
proposal before the deadline.  The editor of the proposal will have to
send invitations to all authors through \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} by clicking an \emph{invitation} button. We
urge proposal editors to invite the authors through
\htmladdnormallink{\tt PMS}{http://pms.iram.fr} well before the
deadline to give them enough time to validate their identity before
the deadline. Authors that fail to validate their participation will
automatically be dropped from the proposal.

\htmladdnormallink{\tt PMS}{http://pms.iram.fr} will be opened for
submission of new proposals about two to three weeks before the
deadline\footnote{\htmladdnormallink{\tt PMS}{http://pms.iram.fr}
  remains open at all times for submission of Director Discretionary
  Time proposals.}. Proposers may modify their proposals in
\htmladdnormallink{\tt PMS}{http://pms.iram.fr} until the deadline, in
which case the \emph{submit} button must be activated again after
modification of the proposal. Please avoid last minute submissions
when the network could be congested. If you experience any difficulty
with the submission process in \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr}, please contact us at
\htmladdnormallink{{\tt
    pms-feedback@iram.fr}}{mailto:pms-feedback@iram.fr} for help. You
may also use this e--mail address for bug reports, general questions
and comments.


\subsection{Proposal Category}

Proposals should be submitted through \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} for one of the four categories:

\begin{description}
\item[{\sc Standard:}\/] Proposals that ask for a total of less than
  100\,h of observing time and for the standard capabilities of
  NOEMA's current status (see the following sections).
%and the documentation \htmladdnormallink{\tt An Introduction to
%the IRAM NOEMA interfero\-meter}
%{http://www.iram.fr/IRAMFR/GILDAS/doc/pdf/noema-intro.pdf}).\\
\item[{\sc Time filler:}\/] Proposals that can be considered as backup
  projects to fill in periods where the atmospheric conditions do not
  allow mapping, to fill scheduling gaps, or even to fill in periods
  when only a subset of the standard antenna configurations are
  available. These proposals will be carried out on a ``best effort''
  basis. 
\item[{\sc special:}\/] Exploratory proposals, whose scientific
  interest justifies the attempt to use the array beyond its
  guaranteed capabilities. This category includes for example
  non-standard frequencies for which the tuning cannot be guaranteed,
  non-standard configurations, special needs with respect to
  calibration and more generally all non-standard observations. 
  These proposals will be carried out on a ``best
  effort'' basis. PIs interested in special programs
  should contact the science operation group (sog@iram.fr) well
  before the deadline to discuss feasibility and observing
  strategies.
\item[\sc Large Program:\/] A Large Program should require more than
  100 hours of observing time, spread over a maximum of three years,
  i.e.\ 6 contiguous semesters, or longer for programs requesting more
  than 1000 hours and address strategic scientific issues (for more
  details see the \htmladdnormallink{\tt Large Program Policy}
  {http://www.iram-institute.org/EN/content-page-243-7-158-243-0-0.html}
  on the IRAM web site).  The observing time request should currently
  be based on the availability and performance of {\bf the ten-element
    array}. We might adjust it and/or review the observing strategy in
  response to PI needs and enhanced array's capabilities. In addition,
  less than the standard 50\% of the total scheduled observing time
  will be reserved for {\it Large Programs} using NOEMA at this
  point. This restriction is necessary to account for the significant
  investment of technical time still needed to bring the NOEMA project
  to its full completion in the upcoming years.
\end{description}

The proposal category will have to be specified on the
\htmladdnormallink{\tt PMS}{http://pms.iram.fr} web form and
should be carefully considered by the proposers.\\

Within each of these categories, observations in Band 1, 2, and 3 can
be requested which are described in more detail in
Section~\ref{receiversec} and in Table~\ref{receivertab}.\\

\subsubsection{Short spacing observations} 
\label{shortspace}

Short spacing observations on the 30-meter telescope should be
directly requested on the interfero\-meter proposal web form through
\htmladdnormallink{\tt PMS}{http://pms.iram.fr}. A separate proposal
for the 30-meter telescope is not required.  The interfero\-meter
proposal form contains a box, labeled ``Request for 30-meter short
spacings'' which should then be checked.  The user will automatically
be prompted to fill in an additional paragraph in which the need for
short spacing data should be justified. It is essential to give here
all observational details, including size and type of map, rms noise,
spectral resolution, receiver, and time requested. The following
documents may help to prepare your short spacing observations:
\htmladdnormallink{\tt this
  Presentation}{http://www.iram-institute.org/medias/uploads/file/PDFs/IS-2018/pety-mosaicking.pdf}
(especially page 23 for a brief summary) given at the 10th
Interferometry School and \htmladdnormallink{\tt this Technical
  Report}{http://www.iram-institute.org/medias/uploads/IRAM_memo_2008-2-short-spacings.pdf}.
  %on ``Single-dish observation and processing to produce the
  %short-spacing information for a millimeter interferometer''. 
  For further assistance, please contact the Science Operations Group
  (sog@iram.fr).\\

\subsubsection{Track-Sharing Mode}

Each technical sheet, i.e.\ frequency tuning, can be connected to
several sources in \htmladdnormallink{\tt PMS}{http://pms.iram.fr}.
In case that sources, sharing the same tuning, are located reasonably
close to each other in the sky and need reasonably short integration
times, \htmladdnormallink{\tt PMS}{http://pms.iram.fr} allows the PI
to specify a track-sharing mode (please check the track-sharing box in
the technical sheet in \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr}), which will result in a lower overall
telescope time due to reduced overheads. Please note that
\htmladdnormallink{\tt PMS}{http://pms.iram.fr} will issue a warning
should the maximum distance between the track-shared sources exceed
the recommended 15~degrees and/or should the number of track-shared
sources be larger than 15. These limitations have been chosen, among
other reasons, to allow for gain calibrators that can still be
reasonably close to all sources, and to reduce observing overheads due
to slewing and calibration needs. The feasibility of track-sharing is,
however, not guaranteed even if no warning is given by
\htmladdnormallink{\tt PMS}{http://pms.iram.fr}. In particular,
Doppler tracking will be done by default on the mean LSR velocity of
the targets (requests for other tracking modes should be
justified). Users should check that the spectral lines of the two
targets with the highest velocity difference to the mean velocity will
not move out of the selected frequency range, which is especially
important with respect to the frequency coverage of selected high
spectral resolution chunks.  Therefore, special care has to be applied
when configuring the spectral setup.

\subsection{Configuring PolyFiX with
  ASTRO for PMS}\label{astrosec}\index{ASTRO}

The software \astro\ should be used to set up the receiver and
correlator configuration. A description of the PolyFiX correlator and
of the commands provided in \astro\ to prepare the correlator
configuration can be found in \htmladdnormallink{\tt this PolyFiX
  tutorial}{http://www.iram.fr/~gildas/demos/astro/demo-astro-noema.pdf
}. Please use the \htmladdnormallink{\tt
  latest}{http://www.iram.fr/~gildas/dist/index.html} version of GILDAS. \\

\noindent The essential \astro\ commands are:

\begin{itemize}
%\item {\tt SOURCE}: define a source (velocity)
\item {\tt TUNING}: receiver tuning
\item {\tt BASEBAND}: selection of baseband(s)
\item {\tt SPW}:  selection of chunks to define high resolution spectral windows
\item {\tt PROPOSAL}: exports a script that needs to be uploaded to
  \htmladdnormallink{\tt PMS}{http://pms.iram.fr}
\end{itemize}

\noindent Receiver tuning is done on a fixed grid of LO frequencies,
spaced by 500\,MHz throughout each receiver band, on which the
receiver performance is optimized. For a correct receiver tuning,
either the source LSR velocity or the redshift is needed, or the
(red)shifted frequencies should be used directly. In the latter case,
the LSR velocity (or redshift) has to be set to zero in the source
command. Also, the frequencies of molecular lines from the standard
line catalogue in \astro\ that can be plotted over the spectrum (by
setting {\tt set lines on} in \astro) have to be redshifted by hand,
i.e., a revised molecular catalogue needs to be uploaded in
\astro\ (with {\tt catalogue myfile.lin /LINE}). For more details see the
internal help for the different \astro\ commands and
\htmladdnormallink{\tt this PolyFiX
  tutorial}{http://www.iram.fr/~gildas/demos/astro/demo-astro-noema.pdf}.\\
\\
A typical session in \astro\ would be:\\

\begin{verbatim}
   ! Define a source with LSR velocity
   SOURCE TOTO EQ 2000 09:11:39.786 -
                       30:53:29.257 LSR 7.0

   ! choice of receiver tuning
   TUNING 232.686 LSB 7500
   ! ASTRO will shift the IF centering by 
   ! 180.6MHz to match the tuning grid   

   TUNING 232.686 LSB 7319.4 /ZOOM
   ! Plots the selected receiver band only

   BASEBAND
   ! select all 8 basebands

   ! define and display high resolution
   ! spectral windows (central frequency 
   ! and width specified)
   SPW /FREQUENCY 244.9 0.2
   SPW /FREQUENCY 245.6 0.2
   SPW /FREQUENCY 232.686 0.03
   SPW /FREQUENCY 230.538 0.08
   SPW /FREQUENCY 231.15 0.3
   ...
   PROPOSAL /FILE MyFile.astro
   ! write the series of commands 
   ! to set up the instrument;
   ! THE MyFile.astro NEEDS TO BE 
   ! UPLOADED TO PMS
\end{verbatim}

\noindent The {\tt TUNING} command produces a plot showing the full
15.488\,GHz bandwidth covered with both sidebands. The TUNING command
checks that the LO frequency is located on the 500\,MHz-spaced tuning
grid. If this is not the case, the command moves the tuned frequency
to a neighboring IF center frequency that matches the grid.  The
option {/FIXED\_FREQ} can be used to ignore the tuning grid (e.g., if
using the tuning grid does not cover all desired lines with the
proposed tuning or if a contiguous spectral scan is requested).

\htmladdnormallink{\tt PMS}{http://pms.iram.fr} will only accept to
load \astro\ scripts created with the PROPOSAL command (which uses the
NOEMA OFFLINE syntax). This will allow \htmladdnormallink{\tt
  PMS}{http://pms.iram.fr} to show spectral coverages in a consistent
way for any kind of projects (including line markers at the correct
rest frequency for redshifted sources for instance).

Old NOEMA ONLINE language scripts, i.e.\ those created by the SETUP
command (e.g., from the W17 semester) can be converted by typing in
\astro:

\begin{verbatim}
OBSERVATORY NOEMA ONLINE
@ MyOnLineScript.astro
PROPOSAL /FILE MyOfflineScript.astro
\end{verbatim} 



\section{Observing Procedures}\label{proceduresec}

After a proposal has been accepted, observing procedures will have to
be prepared. All choices have to be finalized. This implies some
additional work with your {\tt local contact}. Non standard
observations may require an in-house collaborator.

The following procedure is a standard one, which can be used for
``normal'' projects (full scale mapping on one object).

\subsection{Setup Procedure}

The standard setup defines the target source(s), configures the
spectral correlator, selects the observing frequency, and leaves the
system ready for receiver tuning.

%\clearpage

\footnotesize{
\begin{verbatim}
!----------------------------------------------------------------------
!
! PR:SETUP-zzzzzzzz.OBS ! Setup procedure for project "zzzzzzzz"
!
!    - Date:          01-Jun-2019
!    - Author:        
!    - PI:            
!    - Local contact: 
!    - Project ID:    zzzzzzzz
!    - Verified by:   person (date)
!
!    - Rating:                       A or B
!    - Number of telescopes assumed: 10
!    - Observing mode:               mapping/detection/moving body,track-sharing/mosaic
!    - Time:                         [A,B,C,D,any] Any = CD (specify ’Any’ if not ABCD)
!      (total hr os/configuration [A,B,C,D,Any] all sources/fields combined)
!
!    - Requested on-source time (h): sumt(Time)
!    - Time per source:              Fraction of time spent per source in case of track 
!                                    sharing
!
!    - Requested sensitivity:        2mJy/20MHz   (e.g., rms at the given representative 
!                                                  frequency)
!    - Additional sensitivity:       0.1mJy/16GHz (e.g., continuum sensitivity)
!    - rms for one mosaic pointing:  RMS_PER_POINTING
!
!    - Requested minimum S/N:	     REQUESTED_SIGNAL_NOISE
!    - Representative Frequency:     REPRESENTATIVE_FREQUENCY in GHz
!
!    - Water limit:                  REQUESTED_WATER_LIMIT
!    - Obs date constraint:	     OBS_DATE_CONSTRAINT
!
!    - Sun avoidance:                SUN_AVOIDANCE
!
!    - Other comments:               SETUP_COMMENT
! 
!------------------------------------------------------------------------
! Do not edit directly, but copy first then 
!
!        All lines marked !**! must be customized.
!            lines marked !* ! can be modified.
!
!------------------------------------------------------------------------
SET\END                           ! Finish previous observation
@ PR:defaults                     ! Restore defaults parameters
!
SET\PROJECT zzzzzzzz              !**! Specify project number for further 
!
SYMBOL GO "@ PR:bserve-all zzzzzzzz" !* ! data processing
CATA SOU INTER_BASE:iram.sou         !* ! 
CATA PHA INTER_BASE:phase-pdb.sou    !* ! 
LET RECEIVER 1                       !**! Choose observing receiver: receiver 1 @ 3mm
!                                                                 receiver 2 @ 2mm 
!                                                                 receiver 3 @ 1mm
! 
LET LOW_LIMIT %LOW_LIMIT%                 !* ! Low elevation limit 15 degrees
SAY "Project 'PROJECT' starting"
!
SYMBOL NAME "NNNN EQ 2000 00:00:00.00 00:00:00.00 LSR 0.0"  !**! Source 
!                                 
LET N_SUBSCANS 45                 !* ! Scan length (in seconds)
LET N_SCANS 30                    !* ! Number of scans on SOURCE (22.5 minutes = 30*45sec)
LET N_SOURCES 1                   !* ! use SYMBOL NAME if N_SOURCES.EQ.1
IF (N_SOURCES.GT.1) THEN
  LET NAME_SOURCE[1:N_SOURCES]   ".." ".."  !* Enter list of sources (maximum 30)
  LET N_SCANS_SOURCE[1:N_SOURCES] ..   ..   !* Enter time per source (in scans)
ENDIF
!
LET CALIBRATOR_1 "......."        !**! 1st CALIBRATOR
LET CALIBRATOR_2 "......."        !**! 2nd CALIBRATOR
LET CALIBRATOR_3 "......."        !* ! 3rd CALIBRATOR
LET N_CALIBRATORS 2               !* ! Use 2 phase calibrators every N_SCANS
LET N_SUBS_CAL  45                !* ! Scan length on calibrator (in seconds)
LET N_SCANS_CAL  3                !* ! Nb scans on each calibrator (3 scans)
                                
LET FSWI_CAL  .FALSE.             !* ! No fast-switching by default

LET N_MOSAIC 0                    !* ! No mosaic mode
IF (N_MOSAIC.NE.0) THEN
   DEFINE REAL X_MOSAIC[N_MOSAIC] Y_MOSAIC[N_MOSAIC] T_MOSAIC[N_MOSAIC] /GLOBAL
   LET X_MOSAIC .. ..            !* ! offsets in arcsec
   LET Y_MOSAIC .. ..            !* ! offsets in arcsec
   LET T_MOSAIC .. ..            !* ! in units of N_SUBSCANS
ENDIF
!
LET SOLVE_POINT YES      
LET SOLVE_FOCUS YES
!
LET FOCUS_RECEIVER 'RECEIVER'     !* ! Focusing on observing receiver 
LET POINT_RECEIVER 'RECEIVER'     !* ! Pointing on observing receiver 
!
LET POINT_SOURCE_1 "......."      !**! 1st pointing source
LET POINT_SOURCE_2 "......."      !* ! 2nd pointing source
LET FOCUS_SOURCE_1 "......."      !**! 1st focusing source
LET FOCUS_SOURCE_2 "......."      !* ! 2nd focusing source
!
SET\UNLOCK
!
LINE MYLIN 90.0000 LSB 6000.000 /RECEIVER 1
BASEBAND HLO 1 /RECEIVER 1
BASEBAND HLI 1 /RECEIVER 1
BASEBAND HUI 1 /RECEIVER 1
BASEBAND HUO 1 /RECEIVER 1
BASEBAND VLO 1 /RECEIVER 1
BASEBAND VLI 1 /RECEIVER 1
BASEBAND VUI 1 /RECEIVER 1
BASEBAND VUO 1 /RECEIVER 1
!
! PLUS high spetcral resolution chunks
SPW /CHUNK 20 to 36 /BASEBAND HLO /RECEIVER 1
SPW /CHUNK 20 to 36 /BASEBAND VLO /RECEIVER 1
SPW /CHUNK 10 to 26 /BASEBAND HLI /RECEIVER 1
SPW /CHUNK 10 to 26 /BASEBAND VLI /RECEIVER 1
SPW /CHUNK 20 to 36 /BASEBAND HUO /RECEIVER 1
SPW /CHUNK 20 to 36 /BASEBAND VUO /RECEIVER 1
SPW /CHUNK 10 to 26 /BASEBAND HUI /RECEIVER 1
SPW /CHUNK 10 to 26 /BASEBAND VUI /RECEIVER 1
!
!
IF (N_SOURCES.GT.1) THEN
  SOURCE 'NAME_SOURCE[1]' /TYPE OBJ         
 ELSE
  SOURCE 'NAME' /TYPE OBJ          
ENDIF
!
SET\RECE 'RECEIVER' ! Choose receiver band for the observation
!
SET\OBS
!
LOAD /FREQUENCY                          ! Load frequency, but don't move antenna now
!
! Make sure any changes in the spectral configuration will be detected:
SET\LOCK
!
LET CHANGE_SPECTRAL .FALSE.                 !* ! .TRUE. if need to switch to broad_band 
!                                              !(not needed with PolyFiX)
IF (CHANGE_SPECTRAL) THEN
   SPECTRAL /BROAD
ENDIF
!
SET SHOW OFF
!
TYPE PR:clean.obs
SAY "Project zzzzzzzz   Type: TYPE /  Category: CATEGORY" !**!
SAY " "
SAY "        Tuning Receiver "'RECEIVER'":              1           " !**!
SAY " "
!
! Insert here any other instructions to the operator/astronomer
!
SAY "Frequency sent, receivers may be tuned"
SAY "Execute all observations by typing GO"
SAY " "
SAY "Type END when project is finished"
SAY " "
SYMBOL PROCEED /INQUIRE "Type RETURN to remove this page: "
SET SHOW ON
SET SHOW ON
\end{verbatim}
}

\normalsize

\noindent All information appearing on lines marked {\tt !**!} must
have been supplied in the observing proposal, lines marked {\tt !* !}
will use default values if not specified. The remaining part of the
procedure will be defined by IRAM personal (your {\tt local contact},
usually). The project number (zzzzzzzz in this example) is assigned by
IRAM when observing proposals are received. After final checking by
IRAM staff, this file will be given to the {\tt operators} and {\tt
  Astronomers on Duty}, together with a copy of the proposal and any
accompanying information the {\tt PI} may find useful.  The {\tt
  on-duty astronomer} will fill in a {\tt NOTE file} that summarizes
the individual conditions and particular problems encountered during
each track observed. The {\tt NOTE file} will provide some suggestions
in cases where the data calibration is not straight-forward. A copy of
it will be given to the {\tt PI} when he/she visits Grenoble for data
reduction after the project is completed.








\subsection{Phase Calibrator List} \index{phase calibrator}

The current
\href{http://www.iram.fr/IRAMFR/PDB/bure/phase-pdb.sou}{\tt list of
  phase calibrators} used at NOEMA includes over 3000 objects.  Flux
densities at 85\,GHz are indicated in Jy. The flux density is followed
by the spectral index if measured, or 0 if no measurement is
available. The last column gives the date, at which the flux has been
measured. Be careful: most if not all sources are variable (both flux
and spectral index vary). All coordinates are equatorial J2000.0.

%The planets are not sufficiently point-like to be used as bandpass
%calibrators in any configuration.
%
%To find phase calibrators for your source, use the \astro\ procedure name {\tt FIND\_CALI.ASTRO}.


\section{Array Operation}

Since projects are typically spread over several months, the presence
of visiting astronomers when their observations are scheduled is
practically impossible. In the course of observations and data
processing, four ``people'' will play a role: the {\tt proposal PI
  (PI)}, i.e.\ any member of the team that proposed the observations,
the {\tt local contact}, \index{local contact} the {\tt on-duty
  astronomer}, i.e. an IRAM staff member present on the site, and the
array {\tt operator}. The {\tt local contact} is an IRAM astronomer
assigned to each project that does not have an in-house collaborator.
His/her role is to help the {\tt PI} in preparing the observations and
in properly ca\-li\-brat\-ing the data. In case of any problem,
question, or doubt, the {\tt PI} should contact his {\tt local
  contact}. The {\tt PI} can monitor the progress of his project on
the web: {\tt
  \href{http://www.iram.fr/IRAMFR/PDB/ongoing-last.html}{http://www.iram.fr/IRAMFR/PDB/ongoing-last.html}};
this page is updated three times per day. Note that checking results
obtained in a given configuration, making intermediate data
reductions, etc.\ is not the responsibility of the {\tt local
  contact}. In certain cases, and upon request, remote login to a
VISITORS account on the Grenoble computers can be granted to the {\tt
  PI} to help him/her in this task.

The array is regularly operated by one {\tt operator} and one {\tt
  on-duty astronomer}. The {\tt operator} has responsibility for
conducting all observations, following pre-established observing
procedures or under the supervision of the {\tt on-duty astronomer} in
case of unanticipated events. {\tt Operators} have also full authority
for all safety measures.  Receiver tuning is done by the {\tt
  operator}. The {\tt on-duty astronomer} must assess the data quality
during the observations by monitoring the array performance on
standard calibrators. The {\tt PI} usually will not be present on the
site, but is expected to come to Grenoble for data calibration, once
the project is finished.

\subsection{Observations}

The PI must specify all aspects of his/her program in an observing
procedure. Standard observations can be made using general, parametric
procedures. An example is given in Sect.\,\ref{proceduresec}.

The operator will execute the observing procedure, and the on-duty
astronomer will monitor the data quality by examining the observations
of phase calibration sources. \index{phase calibrator} In the case of
peculiar observing conditions (high or exceptionally low phase
drifts, calibrators too weak, etc.), the on-duty astronomer has full
authority to modify the parameters of the observing procedures.
He/She will, of course, try to consult with the {\tt PI} or {\tt local
contact}.

Non-standard observations may require a specific arrangement with the
{\tt local  contact} or {\tt on-duty astronomer}, or may even require
an in-house collaborator.

\subsection{Data Handling}

Raw data, corresponding to individual dumps of the correlator buffers,
are not stored. Instead, a real-time software applies automatic
calibrations (clipping corrections, atmospheric model, etc.) before
writing on disk. This pre-calibrated data is archived daily, and
sorted on a project by project basis.

Except for specific experiments, {\tt PIs} will only have access to
the sorted data, which contain the source data and all the calibration
measurements acquired by the observing procedure. {\tt PIs} will have
exclusive access to their data for a three year proprietary period 
(counting from the end of the last semester of observations of the project), 
but no exclusive rights over the
calibration data, which are duplicated in special data files to
monitor a posteriori the performance of the  interferometer.

Off-line calibration (RF bandpass, phase, flux, and secondary
amplitude calibration) is the {\tt PI}'s responsibility. It is
possible to recalibrate the data for atmospheric transmission and
receiver temperature. Recalibrating the IF bandpass is not possible.

\section{Documentation and Help}

NOEMA is a complex instrument. Previous knowledge of interferometry is
necessary to use it correctly, and reading a standard textbook for
this field is highly recommended (e.g., Thompson A.R., Moran J.M., and
Swenson G.W., 2001 {\em Interferometry and Synthesis in Radio
  Astronomy. Second Edition}, John Wiley \& Sons, Eds.). Information
specific to the IRAM Northern Extended Millimeter Array (NOEMA) is
available on the
\href{http://iram-institute.org/EN/content-page-96-7-56-96-0-0.html}{\tt
  NOEMA documentation web pages} and in the following documents:

\begin{itemize}
\item{NOEMA
\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/astro-html/astro.html}{\astro\
Users Guide:}}\\ \astro\ is a graphic program to help planning
%\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/astro-html/astro.html}{\tt astro
%Users Guide:}}\\ astro is a graphic program to help planning
observations. It is particularly useful for complex observing programs
such as series of  snapshots on many sources or complex line setups
\item{NOEMA
    \href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/pdbi-cookbook-html/pdbi-cookbook.html}{\tt
      Calibration
%Cookbook:}}\\ A hitch-hiker's guide to calibrating NOEMA data with \clic\ 
  Cookbook:}}\\ A guide to calibrating NOEMA data with \clic\
\item{NOEMA
    \href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/clic-html/clic.html}{\tt
      CLIC Users Manual:}}\\ Detailed documentation of the off-line
  calibration program. It assumes the user has previous knowledge of
  interferometry
\item{NOEMA
    \href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/map-html/map.html}{\tt
      Mapping Cookbook:}}\\ A guide to produce and analyze images from
NOEMA with the \gildas\ software
%NOEMA with the gildas software
\item{\href{http://www.iram.fr/IRAMFR/GILDAS/doc/html/gildas-intro-html/gildas-intro.html}{\tt
      \gildas\ Users Manual:}}\\ Documentation of the mapping and
  display
software. \gildas\  \index{GILDAS} is an image processing system with many
% software. gildas  \index{GILDAS} is an image processing system with many
capabilities, and the documentation  assumes the user has a basic
knowledge of image processing
\end{itemize}

\noindent Although these manuals are updated relatively frequently,
only the on-line help within the programs has the latest revisions.


\newpage

\addcontentsline{toc}{section}{Index}
\printindex

\end{document}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
