The next deadline for the submission of observing proposals for the IRAM 30m telescope is March 8th, 1999 24:00h (MET). The scheduling period extends from May 15, 1999 to November 15, 1999, covering roughly the summer period at Pico Veleta. Proposals will be considered only for the observatory's standard heterodyne receivers at wavelengths of 3, 2 and 1.3 mm. Emphasis will be put on proposals for 3 and 2 mm.
Roughly 3000 hours of observing time will be available, which should allow scheduling of a few longer programmes (up to hours).
The main news, proposal formalities, details of the various receivers, and observing modes are described below.
The receiver cabin, which was completely rebuilt last September, has since been used without major problems. In particular, all four new generation receivers (A100, A230, B100 and B230; designated according the dewar A or B they are housed in and according to the frequency, in GHz, they are centered on) perform as expected (see IRAM Newsletter No. 36 and below). The automated tuning available with the new receivers gives fast and reproducible results. Owing to the strong rejection of the image band in all new receivers and to the new calibration unit, the precision of the temperature calibration is now improved.
A backup dual frequency receiver has been built so that it may be expected that two receivers (orthogonally linearly polarized) will always be available for each of the 3 and 1.3 mm atmospheric windows during the upcoming scheduling period. The 2mm window will be served with the old 2MM receiver.
In addition to the two traditional ways of submitting IRAM proposals, by normal mail and by fax, we now accept proposals submitted electronically (see two sections above). A new tool is available for estimating the total observing time needed for a given observation. This new Time Estimator is described in the contribution by David Teyssier in the next section of this Newsletter. Use of the Time Estimator which employs the most recent receiver and telescope data is recommended for all technically standard proposals.
Valid proposals, whichever way they are submitted, consist of the official
cover page, up to two pages
of text describing the scientific aims, and up to two more pages of
figures, tables, and references.
The official cover page, in postscript or in Latex format,
may be obtained by anonymous ftp
from iram.fr in directory
dist/proposal, as well as a Latex style file proposal.sty;
or on the World Wide Web
at URL http://iram.fr/. In case of problems, contact the secretary, Cathy
Berjaud (e-mail: email@example.com).
Do not use characters smaller than 11pt, which could make your proposal
illegible when copied or faxed. For the same reasons, also avoid sending
figures with grey scale maps except when the proposal is
Applications should be addressed to:
IRAM Scientific Secretariat,
Domaine Universitaire de Grenoble
300, rue de la piscine,
F-38406 St. Martin d'Hères, France.
All proposals must reach the Secretariat before March 8th, 1999 24:00h (MET). Proposals sent by Fax ((33/0) 476 42 54 69) will be accepted, provided they arrive in a readable form. Except for a duplicate of the source list (see below), no proposal should be sent by e-mail. The Principal Investigator will receive by return mail an acknowledgement of reception and a proposal number.
To avoid the allocation of several numbers per proposal, send only one copy of your proposal, either by mail or by fax or electronically.
On the title page, you must fill out the line `special requirements' if you request either spectral line on-the-fly observations, or the polarimeter, service or remote observing, or specific dates for time dependent observations. If there are periods when you cannot observe for personal reasons, please specify them here; beware, however, that such personal 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) Also specify on the cover sheet which receivers you 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 your source list. This list must imperatively 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 be typed or printed following the format indicated on the proposal form (please, do not hand write). If your source list is long (e.g. more than 15 sources) you may print it on a separate page, keeping the same format.
The scientific aims of the proposed programme should be explained in 2 pages of text maximum, plus up to two pages of figures, tables, and references. Proposals should be self-explanatory, clearly state their aims, and explain the need of the 30m telescope. The amount of time requested should be carefully estimated and justified . It should include all overheads (see below).
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.
If time has already been given to one 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.
In all cases, indicate on the first page whether your proposal is (or is not) the resubmission of a previously rejected proposal or the continuation of a previously accepted 30m telescope proposal. In case of a resubmission, state very briefly in the introduction why the proposal is being resubmitted (e.g. improved scientific justification).
A handbook (``The 30m Manual'') collecting most of the information necessary to plan 30-m telescope observations is available . 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 through the IRAM Granada web pages (http://www.iram.es). A catalog of well calibrated spectra for a range of sources and transitions (Mauersberger et al. ) is very useful for monitoring spectral line calibration.
The On-the-Fly observing mode (OTF) is available for heterodyne observations since more than two years. Considerable progress was made in making the control of the observations and the data reduction user friendly. Documentation is available on the web (http://www.iram.es). Due to the complexity of the OTF observing mode we advise proposers without a demonstrated experience of this technique on the 30m telescope to consult, or if opportune even involve in their proposal, an astronomer with such experience. David Teyssier of the Granada staff (e-mail: firstname.lastname@example.org) serves as the principal contact in OTF matters.
Frequency switching is available. It used to yield satisfactory baselines within certain limitations (maximum frequency throw of 45 km/s, backends, phase times etc.; for details see ). At present, up to 3 receivers can be frequency switched simultaneously. Baselines are ordinarily flatter when using one single receiver. Little experience exists however with the new generation receivers.
Many proposers underestimate the time needed to carry out their programme, even under excellent weather conditions. We ask you to pay special attention to this matter as a serious time underestimate may be considered as a sure sign of sloppy proposal preparation. The new Time Estimator tool hopefully helps to avoid such problems.
Observing time estimates must take into account:
A technical report explaining how to estimate the telescope time needed to reach a given sensitivity level in various modes of observation was published in the January 1995 issue of the IRAM Newsletter . It has been included in the 30-m telescope Manual . You are asked to follow the guidelines given in this report (or to justify particular requirements) in your proposal.
A new Time Estimator is now available on the IRAM web pages. It is described in the contribution by David Teyssier in this Newsletter. This tool handles all spectroscopic observing modes, albeit in slightly simplified forms, available at the 30m telescope. For the simplest, but most frequent observing strategies a realistic total observing time is calculated which includes all relevant dead times, various calibration observations, receiver tuning, and a minimum of other checks. Since the tool uses the most recent receiver and telescope parameters, it gives in most cases the best available estimate of the total observing time. Novice users of the 30m telescope are particularly invited to use this tool in order to avoid the serious underestimation of observing time noted sometimes in previous proposals.
To facilitate the execution of short ( 8 h) programmes, we propose ``service observing'' for some easy to observe (e.g. short, single source) programmes with only one set of tunings. Observations are made by the local staff using precisely laid-out instructions by the principal investigator. For this type of observation, we request an acknowledgement of the IRAM staff member's help in the forthcoming publication. If you are interested by this mode of observing, specify it as a ``special requirement'' in the proposal form. IRAM will decide which proposals can actually go to that mode.
This observing mode where the remote observer actually controls the observations very much like on Pico Veleta, is available from the downtown Granada office as before, but now also from Grenoble. The prospective remote observer receives a quick introduction into the peculiarities of this observing mode, but full time support like on the telescope is not available. Therefore this observing mode is restricted to technically easy projects and to experienced 30m users. Economic aspects suggest that the duration of remote observations from Grenoble should not exceed about 40 hours. The prospective remote observer should note ``remote observing from Grenoble or Granada'' as a special requirement in the proposal cover sheet.
This section gives all the technical details of observations with the 30m telescope that the average user will have to know. See also the concise summary of telescope characteristics published on the IRAM web pages.
The optical layout of the new receiver cabin allows simultaneous observations with up to 4 heterodyne receivers like in the past. Table 2 lists the combinations expected to be possible in the upcoming scheduling period. A100 and A230 refer to the new generation receivers centered at 100 and 230 GHz, respectively, and housed in Dewar A. which is served in reflection by the beam divider. B100 and B230 are the orthogonally polarized receivers housed in dewar B. The 2MM receiver is served in transmission.
These receivers, housed in dewar A, admit beams which are, in Nasmyth coordinates, horizontally polarized.
The nominal tuning range of the receiver A100 (H-linear polarization in Nasmyth coordinates) is 83.5 - 115.5 GHz; its IF bandwidth is about 500 MHz. SSB receiver noise temperature is 80 K or less over the entire band; the image side band rejection is at least 20 dB. The receiver may actually tune to somewhat lower than nominal frequencies (down to GHz), but performance is not guaranteed.
The receiver A230 can nominally be tuned between 200 and 255 GHz. SSB receiver noise temperature ranges between 100 K near 220 GHz and 300 K at the highest frequencies. At 230.5 GHz, values near 150 K were measured. Image band rejection is of the order of 10 dB, the radio frequency bandwidth is GHz at 3 dB. The receiver may actually tune to somewhat higher than nominal frequencies (up to GHz), but performance is not guaranteed.
Both receivers can be tuned entirely from the control room. Tuning is rapid and repeatable, usually not exceeding 20 min for all 4 new generation receivers.
These receivers are housed in dewar B admitting (in Nasmyth coordinates) vertically polarized beams. These receivers perform very much like those in dewar A with respect to noise, image band rejection, IF bandwidth, and nominal tuning range. Please consult the Time Estimator for details.
B100 replaces the decomissioned receiver 3MM1 as the standard pointing receiver.
The plan for the refurbishment of the receiver cabin forsees installation of two more pairs of new generation receivers housed in dewars C and D. Work on these dewars, which are expected to have each a pair of mixers centered at 2mm and a higher frequency, is well advanced, but not enough to make them available during the next observing session.
This ``old'' generation receiver still has good and reliable performance over most of its band from 129 GHz to 183 GHz.The instantaneous IF bandwidth is 500 MHz. Receiver temperatures ranges from 70 to 150 K (130 to 155 GHz), and 150 to 400 K (155 to 183 GHz).
Polarimeters have been constructed by IRAM for measurements of circular polarization. They have already been used on the telescope (see e.g. the March 1994 issue of the IRAM Newsletter). These polarimeters have been modified for the optical layout of the new receiver cabin, but no experience of their performance exists yet. In case you consider observations of circular polarization, please contact IRAM (preferentially B. Lazareff or C. Thum) to discuss what might actually be possible.
A new IF polarimeter has been built and will be tested at the telescope soon. This polarimeter which can work at any frequency where two orthogonally polarized receivers are available measures all Stokes parameters for spectra no wider than 20 MHz. Proposals are invited for this polarimeter, but they will be scheduled only if and inasmuch as the tests of the instrument turn out to be positive. Interested observers are invited to check with the undersigned.
The telescope efficiencies (main beam and aperture efficiency) are given in Appendix A of ``The 30m Manual'' and the IRAM newsletter No. 18, (November 1994). A one-page summary of the telescope system is on the web (http://www.iram.es/Telescope/systsumm.ps).
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 and 800'' (see [, ] for details). Astronomers should take into account this error beam when converting antenna temperatures into brightness temperatures.
The aperture efficiency depends somewhat on the elevation, particularly at shorter wavelengths. This gain/elevation effect is evaluated in .
There are 3 types of spectral line backends which can be individually connected to any 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 connected to up to four different receivers. Each unit can be shifted in steps of 32 MHz relative to the center frequency of the connected receiver.
Pointing sessions are made every one to two weeks; at present, the fitted pointing parameters yield an absolute rms pointing accuracy of better than 3'' . The relative alignment of the various receivers is of the order of 2'' and is much more stable in the new cabin than it was before. Checking the pointing, focus, and receiver alignment is the responsibility of the observers (use a planet for alignment checks). Systematic (up to 0.3 mm) differences between the foci of various receivers are present. It is recommended to focus on the 1mm receiver when used. The foci should be carefully monitored. Not doing so may result in broadened and distorted beams ().
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. Guélin, J. Cernicharo 1993 Astron. Astrophys. 274, 144-146.
A Small Users' Guide to NOD2 at the 30m telescope A. Sievers (Feb. 1993)
A. Greve, M. Dan, J. Penalver 1993, IEEE Trans. Ant. Propag. AP-40, 1375
Interferometric measurement of tropospheric phase fluctuations at 86 GHz L. Olmi, D. Downes 1992 (IRAM report 238)
Thermal design and thermal behaviour of Radio Telescope structures A. Greve 1992 (IRAM report 253)
Astigmatism in reflector antennas: measurement and correction A. Greve, B. LeFloch, D. Morris, H. Hein, S. Navarro 1994, IEEE Trans. Ant. Propag. AP-42, 1345
Design parameters and measured performance of the IRAM 30-m millimeter radio telescope J. Baars, A. Greve, H. Hein, D. Morris, J. Penalver, C. Thum 1993, Proc. IEEE 82, 687
Frequency switching at the 30m telescope C. Thum, A. Sievers, S. Navarro, W. Brunswig, J. Peñalver 1995, IRAM Tech. Report 228/95.
Cookbook formulae for estimating observing times at the 30m telescope M. Guélin, C. Kramer, and W. Wild; (IRAM Newsletter January 1995, http://iram.fr/newsletter/jan95/jan95.html)
The 30m Manual: A Handbook for the 30m Telescope W. Wild 1995, IRAM Tech. Report 377/95, also available on WWW pages.
NIC: Bolometer User's Guide D. Broguiere, R. Neri, A. Sievers 1996, IRAM Tech. Report.
Pocket Cookbook for MOPS software R. Zylka 1996.
Line Calibrators at 1.3, 2, and 3mm R. Mauersberger, M. Guélin, J. Mart´ın-Pintado, C. Thum, J. Cernicharo, H. Hein, and S.Navarro 1989, A&A Suppl. 79, 217
The Pointing of the IRAM 30m Telescope A. Greve, J.-F. Panis, and C. Thum 1996, A&A Suppl. Ser., 115, 379
The gain-elevation correction of the IRAM 30m Telescope A. Greve, R. Neri, and A. Sievers 1998, A&A Suppl. Ser., 132, 413 - 416
The beam pattern of the IRAM 30m Telescope A. Greve, C. Kramer, and W. Wild 1998, A&A Suppl., 133, 271 - 284
These reports are available upon request (see also previous Newsletters). Please write to Mrs. C. Berjaud, IRAM Grenoble Catherine Berjaud.