Call for Observing Proposals on the Plateau de Bure Interferometer

  Observing proposals are invited for the IRAM Plateau de Bure Interferometer (PdBI), for Nov. 15, 1994 to May 15, 1995 . The deadline for applications is Monday, September 12th 1994 . The available frequency range will be 82 GHz to 116 GHz. We hope to be able to offer in addition two specific opportunities for a fraction of the time
- very long baselines (E24 to W27)
- 230 GHz band for a test and demonstration period
See below for details.

Details of PdBI and operations are given in the document ``An Introduction to the IRAM Plateau de Bure Interferometer'' (copies can be obtained from the address below, or from Internet via the World-Wide-Web and NCSA-Mosaic software; use IRAM home page http://iram.fr/iram.html). Proposers should read this document carefully before submitting any proposal.

Proposals should be sent to IRAM Scientific Secretariat
Interferometer Observing Proposal
300 Rue de la Piscine
F-38406 Saint Martin d'Hères Cedex
FRANCE

IRAM expects to schedule and complete between 20 to 30 projects in this period, with an elapsed time of at least two months between start and end of any given project. Selection will be based on scientific merit, technical feasibility, and adequacy to the instrument.

For this call for proposals, please note the following opportunities:

Very long baselines

We are have started the extension of the baselines of the interferometer, adding stations W20, W23, W27 and N29. We anticipate that only the West track extension (W20, W23 and W27) will be completed before the winter.

Proposals which could benefit from these long East-West baselines can be submitted with an explicit mention ``Long East-West baselines request''. Only a very limited number of such proposals will be considered. Because the whole extension will not be complete, the exact configuration(s) offered is (are) not yet defined. Observers are welcome to make propositions, in particular about the number of extra configurations required (one or 2 ?), but the final choice will remain IRAM's responsibility.

230GHz receivers

IRAM plans to equip 2 antennas with dual-frequency receivers by the end of September. The 4 antennas might be equipped with such receivers by January 1995. The new dual-frequency systems have the following capabilities:

• SSB tuning between 82 and 115 GHz. This brings a factor 2 improvement in sensitivity at 115 GHz when compared to the current system.
• DSB tuning between 210 and 240 GHz. Expected is about 80 K.
• Simultaneous observing at both frequencies. Each of the 6 units of the correlator can be connected to one or the other receiver.

Performances at 230 GHz will require some extensive testing. In order to benefit most from these added capabilities, and to perform the best tests, IRAM is calling for ``Tests or Demonstration projects for the 230 GHz system''. The following restrictive conditions will apply for these projects:

• All projects should be suited for a test period: there is no implied guarantee of completion as for normal proposals.
• Test projects should be feasible with 2 or 3 antennas.
• Pointing accuracy is not expected to be better than 3.

• Test projects should clearly explain what aspect of the interferometer they will test, and what scientific result is expected in case of success.
• Proposals should mention `` Test project for the 230 GHz system'' or `` Demonstration project for the 230 GHz system''.
• Demonstration projects will be carried out only if all 4 antennas are equipped, and only if the previous tests were successful.
• IRAM may require either an in-house collaborator, or the presence of one of the investigators on the site during the test period, or quick data reduction of the project by the investigators in Grenoble, or any combination of the above requests depending on project complexity.
• All projects should have an associated 3mm project to be carried out simultaneously. The associated project will not benefit from the normal ``guarantee of completion'', unless specifically requested in the proposal. Only one proposal should be submitted for both projects.
• The tests will obviously start with short baselines (D configuration). Long baselines (B2 configuration) will be tested also, but use of the ``very long'' baselines is unlikely.

Other relevant information:

Change of scheduling periods:

IRAM will now issue 2 calls for proposals per year, instead of 3. The two scheduling periods are 15-May to 15-Nov (``Summer Period''), and 15-Nov to 15-May (``Winter Period'').

Configurations:

The exact configuration scheme is given in the ``Interferometer'' section of this Newsletter. The ``CD'' (compact) array is obtained with 3 configurations, and the ``BC'' (high resolution) array with 4 configurations, with two configurations in common.

We insist that authors must specify and CAREFULLY justify the requested configuration choice.

Many proposals have been received with insufficient noise estimates. In many cases, a better result can be obtained using lower angular resolution. Combination of all configurations (BCD, 5 configurations in total), is possible, but must be justified even more carefully.

Coordinates and Velocities:

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.

Correlator:

The correlator has 6 independent units, each being tunable anywhere in the 130-610 MHz band, and providing 4 choices of bandwidth/channel configuration: 160 MHz/64, 80 MHz/128, 40 MHz/256 and 20 MHz/256. For the 40, 80 and 160 MHz bandwidths, the two central channels may be perturbed by the Gibbs phenomenon (depending on continuum strength): it is recommended to avoid centering the most important part of the lines in the middle of the band of the correlator unit.

Receivers:

All receivers can be tuned in lower side band with USB rejection of 5-8 dB. In this mode system temperatures () below 150 K for A#2 and A#3, and 180 K for A#1 (Trec 45 and 55 K, respectively), are normally reached below 100 GHz. Higher rejections offer no gain in sensitivity. Accordingly, observations are preferentially done in LSB. If you want a double side band tuning (e.g. to observe one spectral line in each band), please specify it.

This LSB tuning will also be possible between 113 GHz and 115.3 GHz.

Sun Avoidance:

For safety reasons, the sun avoidance circle has been extended to 45 degrees. Please take this into account for your sources AND for the calibrators.

Mosaics:

The PdBI has mosaicing capabilities, but the pointing accuracy may be a limiting factor at the highest frequencies. Please contact S.Guilloteau in case you have questions.

Data reduction:

Proposers should be aware of constraints for data reduction:

• In general, data will be reduced in Grenoble. Proposers will not come for the observations, but will 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.
• IRAM may consider splitting the data reduction in two phases: intermediate calibration and final mapping. Such a splitting is often absolutely necessary for the high resolution images. In such a case, the proposers must be ready to come to IRAM for fast data reduction of the ``compact'' configurations.
• New versions of CLIC are upward compatible with previous ones, but the reverse is not true. Observers wanting to finish data reduction at their home institute should obtain an up-to-date version of CLIC. Since CLIC maintenance is a heavy and tricky task, we insist that observers having a copy of CLIC take special care in maintaining it up-to-date.

Data reduction will be carried out on the dedicated HP workstation.

Local contact:

Depending upon the program complexity, IRAM may suggest an in-house collaborator instead of the normal local contact.

Technical screening:

All proposals will be reviewed for technical feasibility in parallel to being sent to the members of the program committee. Please help in this task by submitting technically precise proposals. Scientific justification should be kept within 2 pages. Note that your proposal must be complete and exact: velocities, position and frequency setup must be exactly specified.

Non-standard observations:

Please contact S.Guilloteau in case of doubt about non-standard program feasibility.

The documentation for the IRAM Plateau de Bure interferometer includes documents of general interest to potential users:

• An Introduction to the IRAM Plateau de Bure Interferometer.
• IRAM Plateau de Bure Interferometer: Calibration CookBook.
• IRAM Plateau de Bure Interferometer: Mapping CookBook.
• IRAM Plateau de Bure Interferometer: Frequency Setup.
• CLIC: Continuum and Line Interferometer Calibration.

• IRAM Plateau de Bure Interferometer: OBS Users Guide.
• IRAM Plateau de Bure Interferometer: Amplitude Calibration.
• IRAM Plateau de Bure Interferometer: Flux Measurements.
• IRAM Plateau de Bure Interferometer: Pointing Parameters.
• IRAM Plateau de Bure Interferometer: Trouble Shooting Guide.

Finally, we would like to stress again the importance of the quality of the observing proposal. The technical preparation of observing proposals is unfortunately often insufficient. In the past, proposals were received which did not even include exact observing frequencies or even source coordinates, or worse, with coordinates with the wrong epoch !... The IRAM interferometer is a powerful, but complex and unique instrument, and proposal preparation requires special care. Information is available in the documentation, and 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 demonstrate how the Plateau de Bure interferometer will bring new information.

Stéphane GUILLOTEAU