Next: VLBI Observations and Call
Up: IRAM Newsletter 60 (July 2004)
Previous: News from the Plateau
Based on our experience in carrying out configuration changes with
limited access to the Observatory, we plan to schedule three
configuration changes next winter. We therefore ask investigators to
submit proposals for all four of the primary configurations of the six
antenna array. A preliminary configuration schedule for the winter
period is outlined below. Please note that the more compact
configurations (C and D) will be available only at the end of January
at the earliest. The scheduling priority will later be adapted
according to pressure in right ascension ranges and may further be
changed during the winter period depending on weather conditions. The
configuration schedule should be taken as a guideline, in particular
when astronomical targets are requested that cannot be observed during
the entire winter period (45 sun avoidance circle).
||Scheduling Priority Winter 2004/2005
||November - December
||December - January
||February - March
||March - April
When the atmospheric conditions are not good enough at
1.3mm, 3mm projects will be observed: in a typical winter, 20-30% of
the time is found to be poor at 1.3mm, but still excellent at 3mm. We
therefore invite proposers to submit proposals also for observations
Under normal operating conditions, IRAM schedules and completes
between 40 to 60 projects during the winter period, with an average
time delay of at least two months between the start and the end of a
project. Selection is based on scientific merit, technical
feasibility, and suitability for the instrument.
Details of the PdBI and the observing procedures are given in the
document ``An Introduction to the IRAM Plateau de
Bure Interferometer''. A
copy can be obtained from the address below or from the World-Wide-Web
at ./IRAMFR/PDB/docu.html. Proposers should read this document
carefully before submitting any proposal.
For this call for proposals, please note the following details.
Proposals should be submitted for one of the five following categories:
The proposal category will have to be specified on the proposal cover
sheet and should be carefully considered by proposers.
- dual freq.:
- Proposals that ask simultaneously for
observations at 3mm and 1.3mm.
- Proposals that ask for 1.3mm data only. 3mm
receivers will be used for pointing and calibration purposes, but the
scientific goals of the proposal rely on the 1.3mm receivers.
- Proposals that ask for 3mm data only.
1.3 mm receivers can still be used to provide either phase stability
information or purely qualitative information such as the mere
existence of fringes.
- time filler:
- Proposals that have to be considered as
backup projects to fill in periods where the atmospheric conditions do
not allow mapping, or eventually, to fill in gaps in the scheduling,
or periods when only a subset of the standard configurations will be
available. These proposals will be carried out on a ``best effort''
- 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.
The six antennas can be arranged in four primary configurations. The
current configurations for the winter period are:
- 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. It is slightly
more extended than the 5-element D configuration: the beam is smaller
( at 100 GHz and
but slightly more elliptical.
- 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 (2 at 100GHz,
0.9 at 230GHz). C alone is also well suited for snapshot
and size measurement experiments.
- B in combination with A already provides slightly higher
angular resolution (1.5 at 100GHz). Short baselines have
been included to facilitate calibration and give
some sensitivity to extended structure, although this is clearly not
the primary goal of the AB configuration. It is mainly used for
relatively strong sources.
- A alone is well suited for mapping or size measurements
of very compact objects. It provides a resolution of at
100GHz, 0.5 at 230GHz. 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).
The four array configurations can be used in different
combinations 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. Enter ANY 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
for further details.
All antennas are equipped with fully operational dual frequency
receivers. The available frequency range will be 82 to 116 GHz for
the 3mm band, and 205 to 245 GHz for the 1.3 mm band. The 3mm and
1.3mm receivers are aligned to within about .
Below 105 GHz, receivers offer best performances in LSB tuning with
high rejection (20 dB): expected system temperatures are 100 to 150 K
for the winter time. Above 110 GHz, best performances are obtained
with USB tuning, low rejection (4 to 6 dB): expected system
temperatures are 250 K at 115 GHz.
The 1.3 mm receivers have DSB tuning with typical T below
50 K. Expected SSB system temperature are 350 to 450 K. The
guaranteed tuning range is 205-245 GHz, but it may be possible to
reach some lower and higher frequencies. Higher frequencies are not
feasible on all antennas because of limitations in the triplers,
however. For details about observing at frequencies beyond the
guaranteed tuning range of the 3mm and 1.3mm receivers, please get in
touch with R.Neri.
The rms noise can be computed from
Investigators have to specify the noise level which is
necessary to achieve each individual goal of a proposal, and
particularly for projects aiming at deep integrations.
- is the system temperature (150 K below 110 GHz, 200 K at
115 GHz, 400 K at 230 GHz for sources at )
- is the conversion factor from Kelvin to Jansky (22 Jy/K at
3mm, 35 Jy/K at 1.3mm)
- is an efficiency factor due to atmospheric phase noise
(0.9 at 3 mm, 0.8 at 1.3 mm).
- 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 (580 MHz for continuum, 40
kHz to 2.5 MHz for spectral line, according to the spectral correlator
The interferometer operates in the J2000.0 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.
The new correlator has 8 independent units, each of which can be placed
in the 110-680 MHz band. 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 continuum is strong. 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 are left out at the low and
the high frequency ends of each subband. The 8 units can be
independently connected either with the 3mm or 1.3mm IFs.
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 R. Neri
in case of doubts.
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, especially for
experienced users of the Plateau de Bure Interferometer. Please
contact R.Neri if you're interested in this possibility.
- In general, data should be reduced in Grenoble. Proposers will
not come for the observations, but may have to come for the reduction.
- 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
- 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.
A local contact will be assigned to every A or B rated proposal which
does not involve an in-house collaborator. He/she will assist you in
the preparation of the observing procedures and provide help to reduce
the data. Assistance is also provided before a deadline to help
newcomers in the preparation of a proposal. Depending upon the
programme 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 programme 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 R.Neri
or R.Lucas to discuss the feasibility.
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 ./IRAMFR/PDB/docu.html
Finally, we would like to stress again the
importance of the quality of the observing proposals. 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.
Roberto NERI (email@example.com)
Next: VLBI Observations and Call
Up: IRAM Newsletter 60 (July 2004)
Previous: News from the Plateau