%comments included:

\section{Call for Observing Proposals on the 30m Telescope}

\subsection{Summary}
%
Proposals for three types of receivers will be considered for the
coming summer semester:

\begin{enumerate}
\item the observatory's  set of four dual polarization heterodyne
receivers centered at wavelengths of 3, 2, 1.3,  and 1.1 mm.
\item the 9 pixel dual--polarization heterodyne receiver array,
HERA, operating at 1.3 mm wavelength
\item a 1.2 mm bolometer array with 37 or 117 pixels
\end{enumerate}

%Emphasis will be put on observations at the
%summer/winter
%longer wavelengths.
%, but 3mm proposals are also encouraged inasmuch
%as they are suited for medium or low quality weather backup onservations.
In total, about 2800 hours of observing time will be available,
which should allow
scheduling of a few longer programmes (up to $\sim 150$ hours).

The main news, proposal formalities, details of the various receivers,
and observing modes are described below.



\subsection{What is new?}

Since November 2005, the telescope runs under a VME and Linux based
new control system (NCS). While some optimization, mainly related to
telescope tracking and timing, is still going on, virtually all
functionality of the old control system  has been recovered. Notable
exceptions are the coordinate system (only J2000 is currently
supported) and the {\tt RASTER} command. OTF,
ONOFF or TRACKING (with frequency switching) commands together with
SIC loops should be used instead. Observations with the rotated
wobbler (non--azimuth wobbling directions) which are of interest
mainly for bolometer mapping, are possible again.

Remote observing will be available from our Granada office, and
later during the summer semester also from Grenoble and, possibly, Bonn.

{The NCS team  maintains a detailed web page
(\htmladdnormallink{../IRAMES\-/ncs30m}{/IRAMES/ncs30m})
where the current status is in depth.

The  {\bf dual polarization HERA} is operational together with its
backends for high (VESPA) and low spectral resolution (WILMA, 4 MHz
filters). Although tuning parameters are now available for a large
range of frequencies, it is still recommended to send us HERA
frequencies in advance.

Like last semester, a {\bf bolometer array}, preferentially  the
117--channel MAMBO~II, which should be used for observing time
estimates, will be available. HERA  and bolometer
observations will be organized in observing pools.



\subsection{Applications}

On the official cover page, please fill in the line `special
requirements' {\bf if you request either polarimetric observations
or service  observing}. If the observations need or have to avoid
specific dates, enter them here. If there are periods when you
cannot observe for personal reasons, please specify them here.
%; be aware, however, that such additional restrictions could make your
%observations difficult or impossible to schedule.

We insist upon receiving, with proposals for heterodyne receivers,
a complete list of frequencies  corrected  for source redshift (to 0.1 GHz)
and precise positions. If in very special cases the proposers do not feel
to be in a position to give this information,
they should take up contact
with the %\htmladdnormallink{scheduler}{mailto:thum@iram.fr}.
scheduler (thum\mbox{@}iram.fr).
The proposers should also specify on the cover sheet which receivers they
plan to use.

In order to avoid useless duplication of observations and to protect already
accepted proposals, we keep up a computerized list of targets.
We ask you to fill out carefully the source list in equatorial
J2000 coordinates.
%are preferred.
This list {\it must contain all the sources} (and only those
sources) for which
you request observing time. To allow electronic scanning of your
source parameters, your list must adhere to the format indicated on the
proposal form (no hand writing, please).
If your source list is longer (e.g. more than 15 sources) than what
fits onto the cover page, please use the  \LaTeX
%macro {\tt \begin{verbatim}\extendedsourcelist\end{verbatim}}.
macro \verb+\extendedsourcelist+.

A scientific project should not be artificially cut into several small
projects, but should rather be submitted as one bigger project, even if
this means 100--150 hours of observing time.

If time has already been given to a project but turned out to be
insufficient, explain the reasons, e.g. indicate the amount of time
lost due to bad weather or equipment failure; if the fraction of time
lost is close to 100\%, don't rewrite the proposal, except for an
introductory paragraph. For continuation of proposals having led to
publications, please give references to the latter.


\subsection{Reminders}

For any questions regarding the telescope and the control programs,
we recommend to consult the NCS web pages
(\htmladdnormallink{../IRAMES/ncs30m}{/IRAMES/ncs30m})
and our page with the \htmladdnormallink{summary of telescope parameters} 
{/IRAMES/telescope/telescopeSummary/telescope_summary.html}.

%It has been updated recently,
%including now a description of the refurbished receiver cabin.
The report entitled ``Calibration of spectral line data at the IRAM 30m
telescope''
explains in detail the applied calibration procedure. Both documents can be
retrieved from the URL
\htmladdnormallink{../IRAMES/otherDocuments/manuals/index.html.}
                  {\wwwes/otherDocuments/manuals/index.html}
A catalog of well calibrated spectra for a range of sources and transitions
(Mauersberger et al. \cite{Mauer}) is very useful for monitoring spectral
line calibration. A copy of the 30m file with the calibrated spectra can
be downloaded from the \htmladdnormallink{Spanish web site}
{\wwwes/dataarchive/linecal/linecal.30m.gz}.

%The powerful On-the-Fly observing mode (OTF) is available for heterodyne
%observations. Documentation is available on the
%Granada web page. Due to the complexity of the OTF observing mode
%we advise proposers without a demonstrated experience of this technique
%on the 30m telescope to contact
%, or involve in their proposal, an astronomer with such experience.
%*** NAME *** of the Granada staff
%(\htmladdnormallink{{\tt ute@iram.es}}{mailto:ute@iram.es})
%serves as the principal contact in OTF matters.

The astronomer on duty (whose schedule can be found at URL
\wwwes/mainWiki/\-AstronomerOnDutySchedule) should be contacted well
in advance for any special questions concerning the preparation of
an observing run.

Frequency switching is available for both HERA and the single pixel
SIS receivers. This observing mode is interesting for observations
of narrow lines where flat baselines are not essential, although
the spectral baselines with HERA are among the best known in frequency
switching.  Certain limitations exist with respect
to maximum frequency throw ($\le 45$ km/s),
backends, phase times etc.; for a detailed report see \cite{R9}.
This report also explains how to identify mesospheric lines which may
easily be confused in some cases with genuine astronomical lines from cold
clouds.

%Finally, to help us keeping up a computerized source list, we ask you to fill
%in your `list of objects' as explained before.

\subsection{Observing time estimates}

This matter needs special attention as a serious time underestimate may be
considered as a sure sign of sloppy proposal preparation. We strongly
recommend to use the web--based Time Estimator at URL 
\htmladdnormallink{../IRAMES/\-obstime/\-time\_estimator.html}
{\wwwes/obstime/time_estimator.html} ,
whenever applicable. Versions~2.6 and higher handle
heterodyne (single pixel and HERA) as well as bolometer observations with
updated instrumental parameters.
%Suggestions and questions can be addressed to NN (Grewing knows).
%(\htmladdnormallink{aweiss@iram.es}{mailto:aweiss@iram.es}).

If very special observing modes are proposed which are not covered
by the Time Estimator, proposers must give sufficient technical
details so that their time estimate can be {\it reproduced}. In
particular, the proposal must give values for $T_{\rm sys}$, the
spectral resolution, the expected antenna temperature of the signal,
the signal/noise ratio which is aimed for, all  overheads and dead
times, and the resulting observing time. The details of the
procedures on which our time estimator is based are explained in a
technical report published in the January 1995
issue\protect\footnote{\ electronically available
at URL {\tt ../IRAMFR/\-ARN/\-newsletter.html}} 
of the IRAM Newsletter \cite{R10}.

Proposers should base their time request on normal
%\textdefsummerwinter{summer}{winter}
summer conditions, corresponding to %\textdefsummerwinter{7}{4}mm
7mm of precipitable water vapor. Conditions during
afternoons can be degraded due to anomalous refraction. The observing
efficiency is then reduced and the flux/temperature calibration is
more  uncertain than the typical 10 percent (possibly slightly more
for bolometer observations).
If exceptionally good transmission or stability of the atmosphere
is requested which may be reachable only in
%\textdefsummerwinter{quasi--winter}{best winter}
winter conditions, the
proposers must clearly say so in their time
estimate paragraph. Such proposals will however be particularly scrutinized.
%as they may have to be scheduled in our new priority scheme (see above),
%for which only a small fraction of winter time will be reserved.


\subsection{Pooled observing}

%summer/winter
As in  previous  semesters, we plan to pool the bolometer with other
suitable proposals into a bolometer pool. HERA projects will be
pooled with other less demanding project into a HERA pool. Both
pools will be organized in several sessions, occupying a significant
fraction of the totally available observing time.
%As in the previous winters, we plan to reserve a large fraction of the
%semester to pooled observing.
The proposals participating in the pools will be observed by IRAM
staff, the PIs and Co-PIs of participating projects and other
cooperating external astronomers. The pool observations will be
organized by the pool coordinators, St\'ephane L\'eon (bolometers)
and Helmut Wiesemeyer (HERA). The participating proposals are
grouped according to their demand on weather quality, and they get
observed following the priorities assigned by the program committee.
The organization of the bolometer and the HERA observing pools are
described at \htmladdnormallink {../IRAMES/mainWiki/PoolObserving}
{\wwwes/mainWiki/PoolObserving}.

Bolometer and heterodyne proposals which are particularly weather
tolerant qualify as backup for the pools. Participation in the pools
is voluntary, and the respective box on the proposal form should be
checked.

Questions concerning the pool organization can be directed to
the scheduler (thum\mbox{@}iram.fr) or the Pool Coordinators,
St\'ephane L\'eon (leon\mbox{@}iram.es) and Helmut Wiesemeyer
(wiesemeyer\mbox{@}iram.es).



\subsection{Service observing}

To facilitate the execution of short ($\leq$8 h) programmes, we
propose ``service observing'' for some easy to observe  programmes
{\it with only one set of tunings}.
Observations are made by the local staff using precisely laid--out
instructions by the principal investigator.
%This is a passive way of
%observing, no direct interaction with the telescope through OBS being
%possible.
For this type of observation, we request an acknowledgement
of the IRAM staff member's help in the forthcoming publication.
If you are interested in this mode of observing, specify it as
a ``special requirement'' in the proposal form. IRAM will then decide which
proposals can actually be accepted for this mode.

\subsection{Remote observing}

This observing mode where the remote observer actually controls the
telescope very much like on Pico Veleta, will be available from the
downtown Granada office,  and later during the summer also from 
Grenoble and possibly Bonn. The remote stations in Paris and Madrid will be
available later.



\subsection{Technical Information about the 30m Telescope}
This section gives all the technical details of observations with the 30m
telescope that the typical user will have to know. A concise
summary of telescope characteristics is published %in Tab.~\ref{Rxs} and
on the \htmladdnormallink{IRAM web pages}
{\wwwes/telescope/\-telescopeSummary/\-telescope_summary.html}.

\subsubsection{HERA}

The {\bf HE}terodyne {\bf R}eceiver {\bf A}rray is expected to be
available for most of next summer. Whenever possible, HERA
observations will be pooled. The 9 dual--polarization pixels are
arranged in the form of a center--filled square and are separated by
$24''$. Each beam is split into two linear polarizations (after a
successful upgrade in March 2005) which couple to separate SIS
mixers. The 18 mixers feed 18 independent IF chains. Each set of 9
mixers is pumped by a separate local oscillator system. The same
positions can thus be observed simultaneously at any two frequencies
inside the HERA tuning range (210-276 GHz for the first
polarization, and 210-242 for the second polarization).

A derotator optical assembly can be set to keep the 9 pixel pattern
stationary in the equatorial or horizontal coordinates. Receiver
characteristics are listed in Tab.~\ref{Rxs}, and an updated user
manual (version 2.0) is available on our \htmladdnormallink{web
page} {\wwwes/otherDocuments/manuals/HERA_manual_v20.pdf}.


Frequency tuning of HERA, although fully under remote control and automatic,
is substantially more complicated than for the
observatory's other SIS receivers.  HERA observers are therefore
advised to send a list of their frequencies to Granada at least 2
weeks     ahead of their run.

Recent observations have shown that the noise temperature of the
pixels of the second polarization array may vary across the 1 GHz IF
band. The highest noise occurs towards the band edges which are,
unfortunately, picked up when HERA is connected with VESPA whose
narrow observing band is located close to the lower edge of the 1
GHz band. Therefore, while not as important for wide band
observations with centered IF band, the system noise in narrow mode
is higher (factor 1.5 -- 2) as compared to the first
polarization array. We do not recommend
to use the second polarization for frequencies $>241$\,GHz.



HERA can  be connected to three sets of backends:
\begin{itemize}%{$\rhd$}
\item[$\rhd$] VESPA with the following combinations
of nominal resolution (KHz) and maximum bandwidth (MHz):
20/40, 40/80, 80/160, 320/320, 1250/640. The maximum bandwidth can actually
be split into two individual bands for each of the 18 detectors
at most resolutions. These individual bands can be shifted separately
up to  $\pm200$ MHz offsets from the sky frequency
(see also the sections on backends below).
\item[$\rhd$] a low spectral resolution (4 MHz channel spacing) filter
spectrometer
covering the full IF bandwidth of 1 GHz. Nine units (one per HERA pixel)
are available. Note that only one polarization of the full array is thus
connectable to these filter banks.
\item[$\rhd$] WILMA with a 1 GHz wide band for each of the 18 detectors.
The bands have 512 spectral channels spaced out by 2 MHz.
%WILMA will be available after successful completion of the current tests.
\end{itemize}

HERA will be operational in two basic spectroscopic observing modes:
{\it (i)} raster maps\footnote{\ As long as the NCS raster command is
  not operational, the raster pattern has to be traced out with the
  help of a SIC loop.}
 of areas typically not smaller than $ 1'$, in
position, wobbler, or frequency switching modes, and {\it (ii)}
on--the--fly maps of moderate  size (typically $2' - 10'$).
Extragalactic proposals should take into account the current
limitations of OTF line maps, as described in the HERA User Manual, due
to baseline instabilities induced by residual calibration errors.
 HERA proposers should use the web--based
\htmladdnormallink{Time Estimator}{\wwwes/obstime/time_estimator.html}.
For details about observing with HERA, consult the User manual.
The HERA project scientist, Karl Schuster (schuster\mbox{@}iram.fr),
or Albrecht Sievers (sievers\mbox{@}iram.es), the astronomer
in charge of HERA, may also be contacted.


\subsubsection{The single pixel heterodyne receivers}

Four dual polarization SIS receivers are available at the
telescope for the upcoming observing season.
They are designated according to the dewar in which they are
housed (A, B, C, or D), followed by the center frequency (in GHz) of their
tuning range.
Their main characteristics are summarised in Tab.~\ref{Rxs}. All receivers
are linearly polarized with the E--vectors, before rotation in the
Martin--Puplett interfero\-meters,  either horizontal or
vertical in the Nasmyth cabin.
Up to four of these eight receivers can be combined
for simultaneous observations in the four ways depicted in Tab.~\ref{Rxs}.
Note that they cannot be combined with HERA nor with the bolometers.
Also listed are typical system temperatures which apply to average
%\textdefsummerwinter{summer weather (7mm of water)}{winter weather (4mm)}
summer weather (7mm of water) at the center of the tuning range and
at 45\degr\ elevation. All  receivers are tuned by the operators
from the control room. Experience shows that it normally takes not
more than 15 min to tune four such receivers.

\begin{table*}
%\textdefsummerwinter{%here comes the SUMMER caption
\caption{Heterodyne receivers available for the next summer
observing semester. Performance figures are based on recent
measurements at the telescope. $T^{\ast}_{sys}$ is the SSB system
temperature in the $T^\ast_A$ scale at the nominal center of the
tuning range, assuming average summer conditions (pwv = 7mm) and
45\degr\ elevation. $g_i$ is the rejection factor of the image side
band. $\nu_{IF}$ and $\Delta\nu_{IF}$ are the IF center frequency
and width. }
%}{%winter caption
%\caption{Heterodyne receivers available for the next winter
%observing season. Performance figures are based on recent
%measurements at the telescope. $T^{\ast}_{sys}$ is the SSB system
%temperature in the $T^\ast_A$ scale at the nominal center of the
%tuning range, assuming average winter conditions (4mm pwv) and
%45\degr\ elevation. $g_i$ is the rejection factor of the image side
%band. $\nu_{IF}$ and $\Delta\nu_{IF}$ are the IF center frequency
%and width. Note that the 8 standard receivers can be combined in 4
%different ways.}
%end summer/winter caption
\label{Rxs}
\begin{center}
%................Rx....p.....1...2...3...4.....rTg.....IDTr......
% take the first of the following 2 lines for latex2html (does not
% digest @{}
\begin{tabular}{|ccccccccccccl|} \hline 
%\begin{tabular}{|cc@{\,}c@{}c@{}c@{}cccccccl@{}|} \hline
%\textdefsummerwinter{%here comes the SUMMER table
receiver & polari-- & \multicolumn{4}{c}{combinations} & tuning
range
         & $T_{Rx}$(SSB) & $g_i$ & $\nu_{IF}$ & $\Delta\nu_{IF}$
         & $T^{\ast}_{sys}$ & remark \rule{0em}{3ex}\\
  & zation
  &\makebox[1.5em]{1}&\makebox[1.5em]{2}&\makebox[1.5em]{3}&\makebox[1.5em]{4}&
            GHz & K & dB & GHz & GHz & K & \\[0.5ex]\hline
A\,100 & V & 1 & &3& & 80 - 115.5
                     & 60 - 80 & $>20$   & 1.5 & 0.5 & 120  & \rule{0em}{3ex}\\
B\,100 & H & 1& & &4 & 81 - 115.5
                     & 60 - 80 & $>20$   & 1.5 & 0.5 & 120  & 1 \\
C\,150 & V & &2 & &4 & 129  - 183
                     & 70 - 125& 15 - 25 & 4.0 & 1.0 & 200  &  \\
D\,150 & H & &2 &3 & & 129 -  183
                     & 80 - 125& 8 - 17  & 4.0 & 1.0 & 200  & \\[1ex]
A\,230 & V & 1& &3 & & 197  - 266
                     & 85 - 150 & 12 - 17& 4.0 & 1.0 & 450  & 2 \\
B\,230 & H & 1& & &4 & 197  - 266
                     & 95 - 160 & 12 - 17& 4.0 & 1.0 & 450  & 2 \\
C\,270 & V & &2 & &4 & 241  - 281
                     &125 - 250 & 10 - 20& 4.0 & 1.0 & 1000  & 3\\
D\,270 & H & &2 &3 & & 241  - 281
                     &150 - 250 & 9 - 13 & 4.0 & 1.0 & 1000  & 3\\[1ex]
HERA   &H/V & &  & & & 210 -  276
                     & 110 - 380&$\sim 10$& 4.0 & 1.0 & 400  & 2, 4
                                                           \\[0.5ex]\hline

%}{%here comes the winter table
%receiver & polar-- & \multicolumn{4}{c}{combinations} & tuning range
%         & $T_{Rx}$(SSB) & $g_i$ &\  $\nu_{IF}$ & $\Delta\nu_{IF}$
%         & $T^{\ast}_{sys}$ & remark \rule{0em}{3ex}\\
%         & ization &\ AB\ &\ CD\ &\ AD\ &\ BC\ &  GHz & K & dB
%         &\  GHz & GHz & K & \\[0.5ex]\hline
%A\,100 & V & 1 && 3 && 80 - 115.5
%                     & 45 - 65 & $>20$   & 1.5 & 0.5 & 120  & 1\rule{0em}{3ex}\\
%B\,100 & H & 1 &&& 4 & 81 - 115.5
%                     & 60 - 85 & $>20$   & 1.5 & 0.5 & 130  & 1 \\
%C\,150 & V && 2 && 4 & 129  - 183
%                     & 70 - 115& 15 - 25 & 4.0 & 1.0 & 200  &  \\
%D\,150 & H && 2 & 3 && 129 -  183
%                     & 60 - 150& 8 - 17  & 4.0 & 1.0 & 200  & \\[1ex]
%A\,230 & V & 1 && 3 && 197  - 266
%                     & 85 - 185 & 12 - 17& 4.0 & 1.0 & 420  & 2 \\
%B\,230 & H & 1 &&& 4 & 197  - 266
%                     & 95 - 160 & 12 - 17& 4.0 & 1.0 & 420  & 2 \\C\,270 & V && 2 && 4 & 241  - 281
%                    &125 - 290 & 10 - 20& 4.0 & 1.0 & 900  & 3\\
%D\,270 & H && 2 & 3 && 241  - 281
%                     &130 - 300 & 9 - 13 & 4.0 & 1.0 & 900  & 3\\[1ex]
%HERA   &H/V&&  &    && 210 -  276
%                     & 110 - 380&$\sim 10$& 4.0 & 1.0 & 400  & 2, 4
%                                                            \\[0.5ex]\hline
%} %end summer/winter table
\end{tabular}
\end{center}
1: tuning range extended to $\geq 72$ GHz under special conditions (see text)\\
2: noise increasing with frequency\\
3: performance at $\nu<275$ GHz; noisier above 275 GHz.\\
4: the V--array (2nd polarization) of HERA has slighly higher noise
which may vary across the IF band; it should not be used for
frequencies higher than 241 GHz.
\end{table*}


\paragraph{Extended tuning range: 72 -- 80 GHz.}

Several molecules of high astrophysical importance have transitions
in the frequency band 66 -- 80 GHz, i.e. between the atmospheric
$O_2$ absorption band and the low frequency edge of the nominal 3mm
tuning range (see Tab.\ref{Rxs}). Tests have shown that both 3mm
receivers, A\,100 and B\,100 have good performance (good upper
sideband rejection and system temperature) in the range 80 -- 77
GHz. The receivers become increasingly double sideband
below 77 GHz, until their behavior becomes erratic around 72 GHz.
Due to the rapid variation of the image gain, special care must be
exercised with calibration. A new image gain calibration tool is
provided and described in the test report available on the
\htmladdnormallink{IRAM web site} {\wwwfr/veleta.htm} (at
../IRAMFR/PV/veleta.htm). The report includes a set of reference spectra.

Observations in the 72 -- 80 GHz range do not require any special
arrangements. But note that the A\,230 (B\,230) receiver is not
available when the A\,100 (B\,100) receiver is used below 80 GHz.



\paragraph{General point about receiver operations.}

Tuning of the single pixel/dual polarization receivers is now
considerably faster  and more reproducible than before.
Particular frequencies, like those in the range 72 -- 80 GHz or
those near  a limit of the tuning range,
may still be problematic.  In these cases,  we recommend
to check with a Granada receiver
engineer at least two weeks before the observations.
HERA observers, however, are requested to send their frequencies as
soon as their project gets scheduled.


\paragraph{Polarimeter XPOL.}

%An  \htmladdnormallink{IF polarimeter}{\wwwold/$\tilde{}$\,thum/spie.ps.gz}
An  upgrade of the IF polarimeter \htmladdnormallink{\cite{IFpol}}
{\www/~thum/spie.ps.gz} is now  available,
%for observations of compact sources.
where the cross correlation between the IF signals from a pair of orthogonally
polarized receivers is made digitally in VESPA.
The new observing procedure, designated XPOL, generates simultaneous
spectra of all 4 Stokes parameters. The following combinations of
spectral resolution (kHz) and bandwidth (MHz) are available:
40/120, 80/240, and 320/480. %, and 1250/640.
%A few hardware and software complications still exist
%(involving manual wiring of LO cables and manual phase calibration)
%which are expected to be solved early in the next semester.

Although successful XPOL observations were made at many frequencies,
experience is still limited, particularly at 1.3mm wavelength and
with respect to observations of extended sources.
Considerable progress was made in reducing polarization sidelobes, notably
for Stokes V. Interested users should contact C.~Thum for details.
Data reduction software using CLASS enhanced with a
graphical user interface is available (\htmladdnormallink{H.~Wiesemeyer}
{wiesemey\mbox{@}iram.es}). A \htmladdnormallink{short guide}
{\wwwfr/veleta.htm} (at \wwwfr/veleta.htm) describes XPOL observations.
Polarimetry proposals for observation of extended sources should demonstrate
that their observations are feasible in the presence of the known
sidelobes (see \htmladdnormallink{\cite{IFpol}}{\www/~thum/spie.ps.gz}).

%The RF polarimeter based on switching a quarter wave plate is still
%available. Interested observers please
%contact IRAM (preferentially B.~Lazareff or C.~Thum) to discuss what
%might actually be possible this winter.





\subsubsection{MPIfR Bolometer arrays}

The bolometer arrays, \Mone\ (37 pixels) and \Mtwo\ (117 pixels),
are provided by the Max--Planck--Institut f\"ur Radioastronomie. They
consist of concentric hexagonal rings of horns
centered on the central horn. Spacing between horns is $\simeq 20''$.
Each pixel has a HPBW of 11$''$.
We expect that \Mtwo\ will be normally used, but \Mone\ is kept as
a backup.

The effective sensitivity of both bolometers for onoff observations is
%\textdefsummerwinter{39}{$\sim35$}
$\sim 40$ mJy\,s$^\frac{1}{2}$ and
$\sim45$ mJy\,s$^\frac{1}{2}$ for mapping. The {\it rms},
in mJy,  of a \Mtwo\  map is typically
$$ rms = 0.4 f \sqrt{v_{scan} \Delta s} $$
where $v_{scan}$, in arc\,sec/sec, is the velocity in the scanning
direction and $\Delta s$, in arc\,sec, is the step size in the
orthogonal direction. The factor $f$ is 1 (2) for sources of size
$<30''\ (>60'')$. It is assumed that the map is made large enough
that all beams cover the source.
%Since in the mapping mode all beams cover the inner region of the map
%area, \Mtwo\ turns out to be more sensitive if areas of $2'$ and larger
%are to be mapped (see the Time Estimator).
The sensitivities apply to bolometric
%\textdefsummerwinter{conditions (stable atmosphere}{winter conditions}
conditions (stable atmosphere),
($\tau(\small{250{\rm GHz}})\sim$ %\textdefsummerwinter{0.3}{0.25},
0.3, elevation 45 deg, and application of skynoise filtering algorithms).
In cases where skynoise filtering algorithms
%(simply the subtraction of correlated sky noise)  can not be applied
are not or not fully effective
(e.g. extended source structure, atmosphere not sufficiently stable),
the effective sensitivity is typically about a factor of 2 worse. For
those projects,  only atmospheric conditions with
low skynoise (i.e. stable atmosphere, no clouds,
little turbulence) are recommened unless the
expected signal is about 1 Jy/beam or stronger.

The bolometer arrays are mostly used in two basic observing modes, ON/OFF and
mapping. Previous experience with \Mtwo\ shows that the ON/OFF reaches
typically an rms noise of $\sim2.3$ mJy in 10 min of total observing time
(about 200 sec of ON source, or about 400 sec on sky integration time)
under stable conditions.
Up to 30 percent lower noise may be obtained in perfect weather.
In this observing mode, the noise integrates down with time $t$ as
$\sqrt{t}$ to  rms noise levels below 0.4 mJy.

In the mapping mode, the telescope is scanning in the
direction of the wobbler throw (default: azimuth) in such a way
that all pixels see the source once.
% and fully sample the beam.
A typical single map\footnote{\ see also the Technical report by
D.~Teyssier and A.~Sievers on a special fast mapping mode
(IRAM Newsletter No.~41, p.~12, Aug.~1999).}
with \Mtwo\ covering a fully and homogeneously sampled  area of
$150''\times150''$ (scanning speed: $5''$per sec, raster step: $8''$)
reaches an rms of 2.8 mJy/beam in 1.9 hours if skynoise filtering is effective.
Much more time is needed (see Time Estimator) if sky noise filtering cannot be
used.
The area actually scanned ($8.0'\times6.5'$) must be larger than the map size
(add the wobbler throw and the array size ($4'$), the source extent,
and some allowance for baseline determination)
if the EHK--algorithm is used to restore properly extended emission.
Shorter scans may lead to problems in
restoring extended structure. Mosaicing is also
possible to  map larger areas.  Under many circumstances,
maps may be co--added to reach lower noise levels.
%but this may require very sophisticated data reduction
%(please contact the experts).
%Attempts to reach map noise levels below 1 mJy
%are still fraught with poorly understood problems
If maps with an rms$\simlt1$ mJy are proposed, the proposers should
contact R.~Zylka (zylka\mbox{@}iram.fr).

%Another note of caution: mapping of extended sources cannot rely on the
%skynoise reduction algorithm (simple subtraction of correlated sky-noise)
%presently available, and the noise level reached may be at least
%twice as high as that quoted above.

The bolometers are used with the wobbling   secondary mirror
(wobbling at a rate of 2 Hz).
%The wobbling direction which used to be
%fixed in azimuth, can now be freely chosen within some limits (see
%IRAM Newsletter No.~61). This allows in virtually all cases to adapt
%the wobbling/scanning direction to the source under study.
%Nevertheless, t
The orientation of the beams on  the sky changes with
hour angle due to parallactic and Nasmyth rotations, as the array is
fixed in Nasmyth coordinates and the wobbler direction is fixed with
respect to azimuth during a scan.
Bolometer proposals participating in the pool have their observations
(maps and ONOFFs) pre-reduced by a  data quality monitor
which runs scripts in %the newly developed
MOPSIC. This package, complete with all necessary scripts,
is also installed for off-line data analysis in Granada
and Grenoble. It is also available for distribution from the IRAM Data Base for
Pooled Observations or directly from  R. Zylka (zylka\mbox{@}iram.fr).
The older software packages  (NIC \cite{R12} and MOPSI \cite{R13})
are still available, but %will not be updated.
%Time estimators for planning ON/OFF or mapping observations are also available
%\cite{R12,TE2}.
cannot process data obtained with the NCS.

Bolometer proposals will be pooled  together like in previous
semesters along with suitable heterodyne proposals as long as the respective
PIs agree.
%Their time requests should be based on
%``bolometric  conditions'',
%like requests using SIS receivers,
The web--based time estimator handles well the usual bolometer observing
modes, and its use is again strongly recommended. The time estimator uses
rather precise estimates of the various overheads which will be applied
to all bolometer proposals.
If exceptionally low noise levels are requested which may be reachable only
in a perfectly stable %\textdefsummerwinter{(quasi winter)}{(perfect winter)}
(quasi winter)
atmosphere, the proposers must clearly say so in their time estimate
paragraph. Such proposals will however be particularly scrutinized.
On the other extreme, if only strong sources are observed and moderate
weather conditions are sufficient,
the proposal may be used as a backup in the observing pool.  The
proposal should point out this circumstance, as it affects positively the
chance that the proposal is accepted and observed.

%\subsubsection{The 2mm bolometer}
%DIABOLO which currently employs a linear 3 pixel array at 2mm is designed
%for detection of weak and somewhat extended sources. The instrument which
%was used successfully at the 30m telescope last winter, is
%described by X.~D\'esert
%elsewhere in this newsletter. The level of integration
%of the instrument into the 30m telescope's standard control and acquisition
%system is minimal, however, complicating the use of this instrument.
%Obervers interested in using DIABOLO should contact
%X.~D\'esert at the Observatoire de Grenoble for arranging some form of
%collaboration.




\subsection{The Telescope}

\subsubsection{Beam and Efficiencies}

Table~\ref{t:eff} lists the size of the telescope beam for the
range of frequencies of interest. Forward and main beam efficiencies
are also shown (see also the note by U.~Lisenfeld and A.~Sievers, IRAM
Newsletter No.~47, Feb. 2001). The variation of the
coupling efficiency to sources of different sizes can be estimated from
plots in Greve et al. \cite{beam}.

At 1.3 mm (and a fortiori at shorter wavelengths) a large
fraction of the power pattern is distributed in an error
beam which can be approximated by two Gaussians of FWHP $\simeq 170''$
and $800''$ (see \cite{beam} for details).
Astronomers should take into account this error beam when converting
antenna temperatures into brightness temperatures.
A variable and sometimes large contribution to the error beam was known
to come from telescope astigmatism \cite{R7}.
Extensive work during the last years had shown that the astigmatism resulted
from temperature differences between the telescope backup structure and
the yoke. The recent installation of heaters in the yoke by J.~Pe\~{n}alver
has nearly completely removed the astigmatism \cite{astigmatism}.


%The aperture efficiency depends somewhat on the elevation, particularly
%at shorter wavelengths. This gain/elevation effect is evaluated in \cite{g/e}.


\begin{table}
\caption[]{Main observational parameters of 30m telescope.}
%Forward and main beam efficiencies, $\eta_F$ and $\eta_{mb}$,
% and beam width $\theta_b$ (FWHP).}
\vspace{1ex}
\begin{center}
\begin{tabular}{|ccccc|}\hline
 frequency & $\theta_b$ [''] & $\eta_F$ &
  $\eta_{mb}$ \rule{0em}{3ex} & $S_\nu$/T$_A^{\ast}$\\[0.4ex]
[GHz] & (1) & (2) & (3) & [Jy/K] \\[1ex]\hline
  86 &        29   &      0.95 & 0.78 &  6.0\rule{0em}{3ex}\\
 110 &        22   &      0.95 & 0.75 &  6.3\\
 145 &        17   &      0.93 & 0.69 &  6.7\\
 170 &        14.5 &      0.93 & 0.65 &  7.1\\
 210 &        12   &      0.91 & 0.57 &  7.9\\
 235 &        10.5 &      0.91 & 0.51 &  8.7\\
 260 &        9.5  &      0.88 & 0.46 &  9.5\\
 279 &        9    &      0.88 & 0.42 &  10.4\\[1ex]\hline
\end{tabular}
\end{center}

(1) beam width (FWHP). A fit to all data gives:\rule{0em}{3ex}
    \makebox[1.5em]{}$\theta_b$ [''] = 2460 / frequency [GHz]\\
(2) forward efficiency (coupling efficiency to sky) \\
(3) main beam efficiency. Based on a fit of measured
    \makebox[1.5em]{}data to the    Ruze formula:\\
    \makebox[1.5em]{}$\eta_{\rm mb}=1.2\epsilon \exp(-(4\pi R \sigma/\lambda)^2)$\\
    \makebox[1.5em]{}with $\epsilon=0.69$ and $R\sigma=0.07$\\
%(4) in units of Jy/K
\label{t:eff}
\end{table}





\subsubsection {Pointing and Focusing}

With the systematic use of inclinometers the telescope pointing became
much more stable. Pointing sessions are now scheduled at larger intervals.
%Pointing sessions are normally scheduled twice per week; at present,
The fitted pointing parameters typically yield an absolute rms
pointing accuracy of better than $3''$ \cite{pointing}. An effort is
made that receivers are closely aligned.
%, however, alignment can be lost occasionally).
Checking the pointing, focus, and receiver alignment is the
responsibility of the observers (use a planet for alignment checks).
Systematic (up to 0.4 mm) differences between the foci of various receivers
%were noted in the past and may well persist, even with the new
%generation receivers.
can occasionally occur.
In such a case the foci should be carefully monitored and a compromise value
be chosen.  Not doing so may result in broadened and
distorted beams (\cite{R2}).

%\begin{table}
%\caption[]{Summary of 30m telescope characteristics}
%\label{summ}
%\begin{tabular}{|c|}\hline
%supplied by Wolfgang\\ \hline
%\end{tabular}
%\end{table}

\subsubsection {Wobbling Secondary}

\begin{itemize}
\item Beam--throw is $\le 240''$ depending on wobbling frequency.
      At 2 Hz, the maximum throw is $90''$
\item Standard phase duration: 2 sec for spectral line observations, 0.25 sec
for continuum observations.
\end{itemize}

Unnecessarily large wobbler throws should be avoided, since they introduce
a loss of gain, particularly at the higher frequencies, and imply a loss
of observing efficiency (more dead time).

\subsection{Backends}
\label{ss:backends}

The following four spectral line backends are available which can be
individually connected to any single pixel receiver and, if indicated,
also to HERA.

{\bf The 1 MHz filterbank} consists of 4 units. Each unit has 256
channels with 1~MHz spacing and can be connected to different or
the same receivers giving bandwidths
between 256 MHz and 1024 MHz. The maximum bandwidth is available
for only one receiver, naturally one having a 1 GHz wide IF bandwidth.
Connection  of the filterbank in the 1~GHz mode presently excludes the
use of  any other  backend with  the same receiver.

Other configurations of the 1 MHz filterbank include
a setup in 2 units of 512 MHz connected to two different receivers, or 4 units
of 256 MHz width connected to up to four (not necessarily) different receivers.
Each unit can be shifted in steps of 32 MHz relative to the center frequency
of the connected receiver.

{\bf The 100 kHz filterbank} consists of 256 channels of 100 kHz spacing.
It can be split into two halves, each movable inside the 500 MHz IF
bandwidth, and connectable to two different single pixel receivers
(must be set up in narrow band mode).

%{\bf The autocorrelator backend} with up to 2048 channels.
%Available nominal resolutions are 10, 20, 40, 80, 320 and 1250 KHz.
%Nominal bandwidths range from 20 MHz to $2\times 512$ MHz,
%depending on resolution.   The correlator can be split into 8
%independent subbands, each of which can be configured individually, shifted
%inside a 500 MHz IF band, and
%connected to the same or different receivers.  For the larger
%bandwidths (i.e. more than one subband of 80 MHz) there is often a problem of
%platforming, i.e. baselines from the different subbands have
%slightly different power levels.


{\bf VESPA}, the versatile spectrometric  and polarimetric array,
can be connected either to HERA or to  a subset of 4 single pixel receivers,
or to a pair of single pixel receivers for polarimetry.
The many VESPA configurations and user modes are summarized in a
\htmladdnormallink{Newsletter contribution}{\www/ARN/dec02/node6.html}
\cite{vespasummary} and in a
\htmladdnormallink{user guide}{\wwwes/otherDocuments/manuals/vespa_ug.ps},
but are best visualised on a demonstration program which can be downloaded
from \htmladdnormallink{our web page}{\wwwfr/veleta.htm}
at URL \wwwfr/veleta.htm.
Connected to a set of 4 single pixel receivers, VESPA typically provides up to
12\,000 spectral channels (on average 3\,000 per receiver).
Up to 18\,000 channels are possible in special
configurations.  Nominal spectral resolutions range from 3.3 kHz
to 1.25 MHz. Nominal bandwidths are in the range  10 --- 512 MHz.
When VESPA is connected to HERA, up to 18\,000 spectral channels can be used
with the following typical combinations
of nominal resolution (kHz) and maximum bandwidth (MHz):
20/40, 40/80, 80/160, 320/320, 1250/640.

{\bf The  4 MHz filterbank} consists of nine units.
Each unit has 256 channels (spacing of 4 MHz, spectral resolution at 3 dB
is 6.2 MHz) and thus covers a total bandwidth of 1 GHz.
The 9 units are designed for connection to HERA, but a subset of 4 units
can also be connected to the backend distribution box which feeds
the  single  pixel spectral line receivers. All these receivers have a 1~GHz RF
bandwidth except for A100 and B100 (500 MHz only).
At the present time, a 4 MHz filterbank cannot be used simultaneously with
the autocorrelator or the 100 kHz filterbank on the same receiver.

%The raw data from these filterbanks are written to a Linux
%workstation. An off--line calibration macro is available for the basic
%observing modes (PSWITCH, WSWITCH, RASTER), but automatic
%calibration is being prepared. Frequency switching is
%not possible with these low resolution backends. (*** is all that still true?)

%An on--line calibration routine automatically writes calibrated
%spectrometer data, including the 4 MHz filterbanks,
%%Now the on-line reduced data for
%to the Linux machines. The routine, although still experimental, works
%for all observing modes. %, including On--the--Fly.
%A logical link named ``data.30m'' pointing to this file of calibrated spectra
%is made available in all newly created project accounts.

The {\bf wideband autocorrelator WILMA} consists of 18 units. They can
be connected to the 18 detectors of HERA. Each unit provides 512
spectral channels, spaced
out by 2 MHz and thus covering a total bandwidth of 1 GHz. Each band is sliced
into two 500 MHz subbands which are digitized  with 2~bit/1~GHz samplers.
An informative technical overview of the architecture is
available at URL
\htmladdnormallink{../IRAMFR/\-TA/backend/veleta/\-wilma/index.htm}
{/IRAMFR/TA/backend/veleta/wilma/index.htm}.
%
Note that WILMA cannot presently  be connected to any of  the
single pixel receivers.
%\item The 500 channel AOS: ({\em Under repair})\\
%Bandwidth 500 MHz; actual spectral
%resolution 1.5 MHz. Using the AOS with the 3 mm SIS receiver results
%in higher noise at the band edges, so the combination 3 mm SIS + AOS
%is not recommended.








\begin{thebibliography}{99}

%\bibitem{R1}   Receiver tests during the August 1992 period\\
%     M. Carter, J.Y. Chenu, H. Hein, S. Navarro, A. Greve, M. Gu\'elin
%(Sept 92)

\bibitem{R2}   Appendix I: Error beam and side lobes of the 30 m
telescope at 1.3 mm, 2 mm and 3 mm wavelength, in  ``Molecular Spiral
Structure in Messier 51'',\\
S. Garcia-Burillo, M. Gu\'elin, J. Cernicharo
1993,  Astron. Astrophys. {\bf 274}, 144-146.

\bibitem{R3}   A Small Users' Guide to NOD2 at the 30m telescope A.
Sievers (Feb. 1993)

%\bibitem{R4}   Thermal behaviour of mm-wavelength radio telescopes
%\\ A. Greve, M. Dan, J. Pe\~{n}alver %1992 (IRAM report 233)
%1993, IEEE Trans. Ant. Propag. AP--40, 1375

%\bibitem{R5}   Interferometric measurement of tropospheric phase
%fluctuations at 86 GHz\\ L. Olmi, D. Downes 1992 (IRAM report 238)

%\bibitem{R6}   Thermal design and thermal behaviour of Radio
%Telescope structures\\ A. Greve 1992 (IRAM report 253)

\bibitem{R7}   Astigmatism in reflector antennas: measurement and
correction\\ A. Greve, B. Lefloch, D. Morris, H. Hein, S. Navarro
%1993 (IRAM report 289)
1994, IEEE Trans. Ant. Propag. AP--42, 1345

%\bibitem{R8}   Design parameters and measured performance of the
%IRAM 30m millimeter radio telescope\\ J. Baars, A. Greve, H. Hein, D.
%Morris, J. Pe\~{n}alver, C. Thum %1993 (IRAM report 298).
%1993, Proc. IEEE~82, 687

\bibitem{R9}
\htmladdnormallink{Frequency switching at the 30m telescope}
{\wwwes/otherDocuments/manuals/Report/}
\\ C. Thum, A. Sievers,
S. Navarro, W. Brunswig, J. Pe\~nalver 1995, IRAM Tech. Report 228/95.
\\(\wwwes/\-otherDocuments/\-manuals/\-Report/fsw\_doc.ps)

\bibitem{R10} Cookbook formulae for estimating observing times at the
30m telescope
\\ M.~Gu\'elin, C.~Kramer, and W.~Wild\\
(\htmladdnormallink{IRAM Newsletter January 1995}
{\www/ARN/jan95/jan95.html})

\bibitem{R11} The 30m Manual: A Handbook for the 30m Telescope
(version~2), W.~Wild 1995
\\IRAM Tech. Report~377/95,
also available on the web at
\htmladdnormallink{../IRAMES/\-otherDocuments/\-manuals/\-manual\_v20.ps}
{\wwwes/otherDocuments/manuals/manual_v20.ps}

\bibitem{R12} NIC: Bolometer User's Guide
\\D. Brogui\`ere, R. Neri, A. Sievers, and H.~Wiesemeyer 2000,
IRAM Technical Report
(\htmladdnormallink{../IRAMFR/\-GILDAS/\-doc/\-html/\-nic-html/\-nic.html}
{\www/IRAMFR/\-GILDAS/\-doc/\-html/\-nic-html/\-nic.html});\\
\mbox{see also the \htmladdnormallink{GILDAS home page}
                  {/IRAMFR/\-GILDAS/}  at}
/IRAMFR/\-GILDAS/ with further relevant technical reports.

\bibitem{R13} Pocket Cookbook for MOPSI software
\\\mbox{R. Zylka 1996, available at}
\htmladdnormallink
{../IRAMES/\-otherDocuments/\-manuals/\-Datared/\-pockcoo.ps}
{\wwwes/\-otherDocuments/\-manuals/\-Datared/pockcoo.ps}.

\bibitem{Mauer} Line Calibrators at $\lambda =$ 1.3, 2, and 3mm.
\\R.~Mauersberger, M.~Gu\'elin, J.~Mart{\'\i}n--Pintado, C.~Thum,
J.~Cernicharo, H.~Hein, and S.Navarro 1989, A\&A Suppl. 79, 217

\bibitem{pointing} The Pointing of the IRAM 30m Telescope
\\A.~Greve, J.--F.~Panis, and C.~Thum 1996,
A\&A Suppl. 115, 379

\bibitem{g/e} The gain--elevation correction of the IRAM 30m Telescope
\\A.~Greve, R.~Neri, and A.~Sievers 1998,
A\&A Suppl. 132, 413

\bibitem{beam} The beam pattern of the IRAM 30m Telescope
\\A.~Greve, C.~Kramer, and W.~Wild 1998,
A\&A Suppl. 133, 271

\bibitem{TE2} A Time Estimator for Observations at the IRAM 30m Telescope,
D.~Teyssier 1999, IRAM/Granada Technical Note
(\wwwes/\-obstime/\-time\_estimator.html)

\bibitem{vespasummary} VESPA is operational
\\G.~Paubert \& C.~Thum 2002,
\\IRAM Newsletter No.~54, 6
\\(\wwwfr/veleta.htm  and
\wwwes\-/otherDocuments\-/manuals/\-vespa\_ug.ps)


\bibitem{astigmatism} First results from the IRAM 30m telescope
improved thermal control system
\\J.~Pe\~{n}alver, A.~Greve, and M.~Bremer 2002, IRAM Newsletter No.~54, 8

\bibitem{IFpol}A Versatile IF Polarimeter at the IRAM 30m Telescope\\
     C.~Thum, H.~Wiesemeyer, D.~Morris, S.~Navarro, and M.~Torres\\
     in ``Polarimetry in Astronomy'', Ed. S.Fineschi,
     Proc.of SPIE Vol.4843, 272--283 (2003)



\end{thebibliography}


These reports are available upon request (see also previous
Newsletters). Please write to Mrs. C. Berjaud, IRAM Grenoble
(e--mail: {\tt berjaud\mbox{@}iram.fr}).

\signed{
%\htmladdnormallink{Clemens Thum}{mailto:thum@iram.fr},
%\htmladdnormallink{Rainer Mauersberger}{mailto:mauers@iram.es}}
Clemens Thum  \& Rainer Mauersberger}
%\end{document}
