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Based on our experience in carrying out configuration changes with
limited access to the observatory, we plan to schedule four
configuration changes next winter. We therefore ask investigators to
submit proposals for any of the 4 of the primary configurations of the six
A preliminary configuration schedule for the winter period is outlined
below. Adjustments to the provisional configuration planning will be
made according to proposal pressure, weather conditions, the
installation of the NGRx and other contingencies. E.g., depending on
proposal pressure, the time in the A configuration may be
extended. Due to the installation of the new receivers, the foreseen
December session in the C configuration may be postponed and merged
with the March-April session. We therefore may have less time
available in C configuration this winter than in previous years. The
configuration schedule should be taken as a guideline, in particular
when the requested astronomical targets cannot be observed during the
entire winter period (45 sun avoidance circle).
||Scheduling Priority Winter 2006/2007
||January - February
||February - March
||March - April
||April - May
We strongly encourage observers to submit proposals for the new set of
AB configurations that include 730 and 760 meter baselines. For these
proposals we ask to focus on bright compact sources, possibly at high
We invite proposers to submit proposals also for observations at
3mm. When the atmospheric conditions are not good enough at 1.3mm,
3mm projects will be observed: in a typical winter, 20-30% of the
observing time is found to be poor at 1.3mm, but still excellent at
All applications under this call for proposals will have to take into
account that the NGRx cannot be operated simultaneously at more than
one frequency. Investigators will therefore have to make it clear
whether a request is made for one (e.g., 3mm) or two (i.e. 3mm
and 1mm) frequency bands. Proposals that need observations in the
two bands will have to be duly justified.
Proposals should be submitted for one of the six following
The proposal category will have to be specified on the proposal cover
sheet and should be carefully considered by proposers.
The six-element array can be arranged in the following
- Proposals that ask for 3mm data only.
- Proposals that ask for 1.3mm data only.
- dual freq.:
- Proposals may ask for observations at 3mm
and 1.3mm. Note, that these will NOT be simultaneous since the new
generation receivers cannot be operated simultaneously in the two
frequency bands. Proposals should justify the need of both bands and
make it clear which band is priority.
- time filler:
- Proposals that have to be considered as
backup projects to fill in periods where the atmospheric conditions do
not allow mapping, or potentially, to fill in gaps in the scheduling,
or periods when only a subset of the standard configurations will be
- Exploratory proposals: proposals whose
scientific interest justifies the attempt to use the PdB array beyond
its guaranteed capabilities. This category includes, for example,
non-standard frequencies for which the tuning cannot be guaranteed and
more generally all non-standard observations. These proposals will be
carried out on a ``best effort'' basis only.
- Science demonstration proposals that use the
improved figures of the new receivers. Up to 30% of the available
observing time might be given to this category. Please note that the
science demonstration proposals will not be observed should the
expected sensitivity not be reached at the beginning of the observing
The general properties of these configurations are:
The four configurations can be used in different
combinations to achieve complementary sampling of the uv-plane, and to
improve on angular resolution and sensitivity. Mosaicing is usually
done with D or CD, but the combination BCD can also be requested for
high resolution mosaics. Check the ANY bullet in the proposal
form if the scientific goals can be reached with any of the four
configurations or their subsets.
Please consult the documentation on the Plateau de Bure
configurations and the IRAM Newsletter No. 63 (August 4th., 2005:
../IRAMFR/ARN/aug05/aug05.html) for further details.
The installation of the new generation receivers on the Plateau de
Bure corresponds to a significant change of the receivers, transmission
lines and backend. Although the new receivers will ultimately provide
large gains in sensitivities and bandwidths as compared to the present
receivers, they have not yet been tested under real observing
conditions. IRAM will do its utmost so that the performances of the
interferometer equipped with the new generation receivers will be as close
as possible to those which are expected. However, it cannot guarantee
these performances for the coming observing session. We consider
therefore two categories of proposals that will be rated separately:
1) science demonstration proposals (% of the total time)
that can be observed only with the improved noise temperatures that the new
receivers should normally provide. Please check the SD bullet if you
apply for this category.
2) regular proposals that can be done with the current receiver
noise temperatures (i.e. the same as last year).
Both types of proposals may take advantage of the extended baselines
and of the increased useful bandwidth. Conservatively, we plan to limit
the science demonstration proposals to about 1/3 of the
available time. In the case the expected sensitivity will not be reached at
the beginning of the observing session, the science demonstration
proposals will not be observed.
- A alone is well suited for mapping or size
measurements of very compact objects. It provides a resolution of
at 100GHz, 0.35 at 230GHz.
- B alone yields 1.2 at 100GHz and, in
combination with A provides an angular resolution of 1.0 at
100GHz. In addition, because it contains long, intermediate and
some short baselines, it could still be used in a tapered mode when a
project is observed in marginal weather conditions despite some loss
of sensitivity (for backup projects). It is mainly used for
relatively strong sources.
- C provides a fairly complete coverage of the
uv-plane (low sidelobe level) and is well adapted to combine with D
for low angular resolution studies (3.5 at 100GHz,
1.5 at 230GHz) and with B for higher resolution
(1.7 at 100GHz, 0.7 at 230GHz). C alone is also
well suited for snapshot and size measurement experiments.
- D alone is best suited for deep integration and
coarse mapping experiments. This configuration provides both the
highest sensitivity and the lowest atmospheric phase noise.
The sensitivity calculations can be made by using equation (1) below.
Investigators have to specify the noise level which is
necessary to achieve each individual goal of a proposal, particularly
for projects aiming at deep integrations.
The interferometer operates in the J2000.0 coordinate system. For best
positioning accuracy, source coordinates must be in the J2000.0
system; position errors up to may occur otherwise.
Please do not forget to specify LSR velocities for the
sources. For pure continuum projects, the ``special'' velocity
NULL (no Doppler tracking) can be used.
Coordinates and velocities in the proposal MUST BE CORRECT. A
coordinate error is a potential cause for proposal rejection.
At any given time, only one frequency band is used, but with the two
polarizations available. Each polarization delivers a 4 GHz bandwidth,
from IF=4 to IF=8 GHz. The two 4-GHz bandwidths coincide in the sky
frequency scale. The current (narrow-band) correlator accepts
as input two signals of 1 GHz bandwidth, that must be selected within
the 4 GHz delivered by the receiver. In practice, the new IF
processor splits the two input 4-8 GHz bands in four 1 GHz
``quarters'', labeled Q1...Q4. Two of these quarters must be
selected as correlator inputs. The system allows the following
- is the conversion factor from Kelvin to Jansky (22 Jy/K at
3mm, 35 Jy/K at 1.3mm)
- is the system temperature.
You may use for regular
proposals = 150K below 110GHz, 200K at
115GHz, 400K at 230GHz for sources at
and for science demonstration proposals = 100K below 110GHz,
115GHz, 190K at 230GHz for sources at )
- is an efficiency factor due to atmospheric phase noise
(0.9 at 3mm, 0.8 at 1.3mm).
- is the number of antennas (6), and is the number of
configurations: 1 for D, 2 for CD, 2 for BC, and so on.
- is the on-source integration time per configuration
in seconds (2 to 8 hours, depending on source declination). Because of
various calibration observations the total observing time is typically
- is the spectral bandwidth in Hz (up to 2 GHz for continuum,
40 kHz to 2.5 MHz for spectral line, according to the spectral correlator
- is the number of polarizations: 1 for single polarization
and 2 for dual polarization (see section Correlator for details).
where HOR and VER refers to the two polarizations.
- first correlator entry can only be Q1 HOR, or Q2 HOR, or Q3 VER, or Q4 VER
- second correlator entry can only be Q1 VER, or Q2 VER, or Q3 HOR, or Q4 HOR
How to observe two polarizations? To observe simultaneously two
polarizations, one must select the same quarter (Q1 or Q2 or Q3 or Q4)
for the two correlator entries. This will necessarily result in each
entry seeing a different polarization. The system thus give access
to 1 GHz 2 polarizations.
How to use the full 2 GHz bandwidth? If two different quarters
are selected (any combination is possible), a bandwidth of 2 GHz can
be analyzed by the correlator. But only one polarization is available
in that case; this may or may not be the same polarization for the
two chunks of 1 GHz.
Is there any overlap between the four quarters? In fact, the
four available quarters are 1 GHz wide each, but with a short overlap
between some of them: Q1 is 4.2 to 5.2 GHz, Q2 is 5 to 6 GHz, Q3 is
6 to 7 GHz, and Q4 is 6.8 to 7.8 GHz. This results from the combination
of filters and LOs used in the IF processor.
Is the 2 GHz bandwidth necessarily continuous? No: any combination
of two quarters can be selected. Adjacent quarters will result in a
continuous 2 GHz band. Non-adjacent quarters will result in two
independent 1 GHz bands. Note that in any case, the two correlator
inputs are analyzed independently.
Where is the selected sky frequency in the IF band? It would
be natural to tune the receivers so that the selected sky frequency
corresponds to the middle of the IF bandwidth, i.e. 6.0 GHz. However,
this corresponds to the limit between Q2 and Q3. It is therefore
highly recommended to center a line at the center of a quarter.
The correlator has 8 independent units, which can be placed anywhere
in the 100-1100 MHz band (1 GHz bandwidth). 7 different modes of
configuration are available, characterized in the following by couples
of total bandwidth/number of channels. In the 3 DSB modes (320MHz/128,
160MHz/256, 80MHz/512 - see Table) the two central channels may be
perturbed by the Gibbs phenomenon if the observed source has a strong
continuum. When using these modes, it is recommended to avoid
centering the most important part of the lines in the middle of the
band of the correlator unit. In the remaining SSB modes (160MHz/128,
80MHz/256, 40MHz/512, 20MHz/512) the two central channels are not
affected by the Gibbs phenomenon and, therefore, these modes may be
preferable for some spectroscopic studies.
Note that 5% of the passband is lost at the end of each
subband. The 8 units can be independently connected to the first or
the second correlator entry, as selected by the IF processor (see
above). Please note that the center frequency is expressed -as in the
old system- in the frequency range seen by the correlator, i.e. 100
to 1100 MHz. The correspondence to the sky frequency is depending on
the parts of the 4 GHz bandwidth which have been selected as correlator
The software ASTRO has been updated to reflect these new
receiver/correlator setup possibilities. Astronomers are urged to
download the most recent version of GILDAS at ../IRAMFR/GILDAS/
to prepare their proposals.
The old LINE command has been replaced by several new
commands (see internal help):
A typical session would be:
- NGR_LINE: receiver tuning
- NARROW_INPUT: selection of the narrow-band correlator inputs
- SPECTRAL: spectral unit tuning
- PLOT: control of the plot parameters.
! choice of receiver tuning
ngr_line xyz 230 usb
! choice of the correlator windows
narrow_input Q1 Q3
! correlator unit #1, on entry 1
spectral 1 20 520 /narrow 1
! correlator unit #2, on entry 1
spectral 2 320 260 /narrow 1
! correlator unit #3, on entry 2
spectral 3 40 666 /narrow 2
For safety reasons, a sun avoidance circle is enforced at 45
degrees. Please take this into account for your sources and
The PdBI has mosaicing capabilities, but the pointing accuracy may be
a limiting factor at the highest frequencies. Please contact the
Interferometer Science Operations Group (sogiram.fr) in case of
Proposers should be aware of constraints for data reduction:
Data reduction will be carried out on dedicated computers at
IRAM. Remote data reduction is possible, and especially for
experienced users of the Plateau de Bure Interferometer. Please
contact the Interferometer Science Operations Group (sogiram.fr) if
you are interested in this possibility.
A local contact will be assigned to every A or B rated proposal that
does not involve an in-house collaborator. He/she will assist you in
the preparation of the observing procedures and provide help to reduce
the data. Assistance is also provided before a deadline to help
newcomers in the preparation of a proposal. Depending upon the
program complexity, IRAM may require an in-house collaborator
instead of the normal local contact.
All proposals will be reviewed for technical feasibility in addition
to the scientific review by the program committee. Please help in
this task by submitting technically precise proposals. Note that your
proposal must be complete and exact: the source position and velocity
as well as the requested frequency setup must be correctly given.
If you plan to execute a non-standard program, please contact the
Interferometer Science Operations Group (sogiram.fr) to discuss the
The documentation for the IRAM Plateau de Bure Interferometer includes
documents of general interest to potential users, and more specialized
documents intended for observers on the site (IRAM on-duty
astronomers, operators, or observers with non-standard programs). All
documents can be retrieved on the Internet at
- In general, data should be reduced in Grenoble. Proposers will
not come for the observations, but may have to come for the data
- We keep the data reduction schedule very flexible, but wish to
avoid the presence of more than 2 groups at the same time in
Grenoble. Please contact us in advance.
- In certain cases, proposers may have a look at the uv-tables as
the observations progress. If necessary, and upon request, more
information can be provided. Please contact us if you are interested
in this possibility.
- CLIC evolves to cope with upgrades of the PdBI array. The newer
versions are downward compatible with the previous releases. Observers
who wish to finish data reduction at their home institute should
obtain the most recent version of CLIC. Because differences between
CLIC versions may potentially result in imaging errors if new data are
reduced with an old package, we advise observers having a copy of CLIC
to take special care in maintaining it up-to-date.
Note however, that the documentation on
the web has not yet been updated with respect to the new generation
receivers. All information currently available on the new generation receiver
system is given in this call for proposals.
Finally, we would like to stress again the
importance of the quality of the observing proposal. The IRAM
interferometer is a powerful, but complex instrument, and proposal
preparation requires special care. Information is available in the
documentation and at ../IRAMFR/PDB/docu.html. The IRAM staff can help
in case of doubts if contacted well before the deadline. Note that the
proposal should not only justify the scientific interest, but also the
need for the Plateau de Bure Interferometer.
Jan Martin WINTERS
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