The main news, proposal formalities, details of the various receivers, and observing modes are described below.
Since November 2005, the telescope runs under the VME and Linux based New Control System (NCS). A short description of the NCS is given elsewhere in this Newsletter. At the time of writing, the last missing major feature of the first NCS installation, namely observations with HERA, is being implemented. The main restriction, still expected to apply during (part of) the summer semester concerns source coordinates. The only system fully supported now by the NCS is equatorial J2000.0, and we request observers to use this system for their source coordinates and offsets.
NCS upgrades, addition of new features, and smoothing out of imperfections will go on during much of the summer semester. The NCS team maintains a web page (../IRAMES/ncs30m) where the current status is described.
Remote observing is expected to be enabled again sometime during the next semester. Observers of accepted proposals should contact the scheduler (thumiram.fr) about the status at the time.
The 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. Observers should be aware, however, that the second polarization channels tend to be somewhat noisier, and the receiver noise varies substantially across the 1 GHz bandpass in some pixels of the second polarization. A broken pixel is planned to be repaired before the start of the new semester.
Like last semester, a bolometer array, most likely the 117-channel MAMBO II, which should be used for observing time estimates, will be available.
On the official cover page, please fill in the line `special requirements' 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.
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 scheduler (thumiram.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
This list 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 LATEXmacro
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 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.
A handbook (``The 30m Manual'') collects much of the information necessary to plan 30m telescope observations. It is however outdated in many sections, and we recommend also to consult the NCS web pages (../IRAMES/ncs30m)
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 ../IRAMES/otherDocuments/manuals/index.html. A catalog of well calibrated spectra for a range of sources and transitions (Mauersberger et al. ) is very useful for monitoring spectral line calibration. A copy of the 30m file with the calibrated spectra can be downloaded from the Spanish web site.
The astronomer on duty (whose schedule can be found at URL ../IRAMES/groups/astronomy/aodsched.html) should be contacted well in advance for any special questions concerning the preparation of an observing run (e.g. setup of on-the-fly maps etc).
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 ( km/s), backends, phase times etc.; for a detailed report see . This report also explains how to identify mesospheric lines which may easily be confused in some cases with genuine astronomical lines from cold clouds.
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 (URL: ../IRAMES/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.
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 reproduced. In particular, the proposal must give values for , 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 issue2 of the IRAM Newsletter .
Proposers should base their time request on normal summer conditions, corresponding to 4mm of precipitable water vapor. Conditions during afternoons can be degraded due to anomalous refraction. The observing efficiency is then reduced and the temperature calibration is more uncertain than the typical 10 percent. If exceptionally good transmission or stability of the atmosphere is requested which may be reachable only in best winter conditions, the proposers must clearly say so in their time estimate paragraph. Such proposals will however be particularly scrutinized.
As in the previous summer semester, we plan to pool the bolometer and other suitable proposals together in one or more observing sessions. The proposals participating in the pool are observed by Granada staff and cooperating external astronomers, as organised by the pool coordinator. 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 observing pool is described at ../IRAMES/observing/flexible/flexible.html.
Typically, the bolometer proposals are included in the pool, but very weather sensitive heterodyne proposals, in particular those using HERA, may also request inclusion in the pool. Bolometer and heterodyne proposals which are particularly weather tolerant qualify as backup for the pool. Participation in the pool is voluntary, and the respective box on the proposal form should be checked.
Any questions concerning the pool organization should be directed to the scheduler (thumiram.fr) or the Pool Coordinator, Stéphane Léon, leoniram.es.
To facilitate the execution of short (8 h) programmes, we propose ``service observing'' for some easy to observe 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 then decide which proposals can actually be accepted for this mode.
This observing mode where the remote observer actually controls the telescope very much like on Pico Veleta, used to be available from the downtown Granada office, from the MPIfR in Bonn, from the ENS in Paris, from the OAN in Madrid (near Parque de Retiro), and from IRAM in Grenoble. However, due to the transition to the telescope's new control system, remote observing will not be working during several months. Observers are strongly encouraged either to consider service observing for their shorter proposals or to come to the telescope.
Remote observing may possibly become available again later in the summer semester. Potential remote observers are advised to contact the scheduler, Clemens Thum, for the most recent status.
The HEterodyne Receiver Array is expected to be available for most of next summer. The 9 dual-polarization pixels are arranged in the form of a center-filled square and are separated by . 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).
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. 1, and an updated user manual (version 1.9) is available on our web page.
Frequency tuning of HERA, although fully under remote control and automatic, is substantially more complicated than for the observatory's other SIS receivers. A new tuning tool has been developed which speeds up considerably the DSB and SSB tuning of the 18 mixers. Despite this good progress, there may still be some difficult frequency spots. 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 varies 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 dramatic for wide band observations with centered IF band, the system noise in narrow mode is considerably higher (factor 1.5 - 2) as compared to the first polarization array. The problem will be tackled during the next 6 months and improvements will be announced on the HERA page on our Spanish web site.
HERA can be connected to three sets of backends:
HERA will be operational in two basic spectroscopic observing modes: (i) raster maps of areas typically not smaller than , in position, wobbler, or frequency switching modes, and (ii) on-the-fly maps of moderate size (typically ). Extragalactic proposals should take into account the current limitations of OTF line maps, as described in the User Manual, due to baseline instabilities induced by residual calibration errors. HERA proposers should use the web-based Time Estimator. For details about observing with HERA, consult the user manual. The HERA project scientist, Karl Schuster (schusteriram.fr), or Albrecht Sievers (sieversiram.es), the astronomer in charge of HERA, may also be contacted.
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. 1. All receivers are linearly polarized with the E-vectors, before rotation in the Martin-Puplett interferometers, 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. 1. Note that they cannot be combined with HERA nor with the bolometers. Also listed are typical system temperatures which apply to normal summer weather (4mm of water) at the center of the tuning range and at 45 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.
|A100||V||1||3||80 - 115.5||60 - 80||1.5||0.5||120|
|B100||H||1||4||81 - 115.5||60 - 80||1.5||0.5||120||1|
|C150||V||2||4||129 - 183||70 - 125||15 - 25||4.0||1.0||200|
|D150||H||2||3||129 - 183||80 - 125||8 - 17||4.0||1.0||200|
|A230||V||1||3||197 - 266||85 - 150||12 - 17||4.0||1.0||450||2|
|B230||H||1||4||197 - 266||95 - 160||12 - 17||4.0||1.0||450||2|
|C270||V||2||4||241 - 281||125 - 250||10 - 20||4.0||1.0||1000||3|
|D270||H||2||3||241 - 281||150 - 250||9 - 13||4.0||1.0||1000||3|
|HERA||H/V||210 - 276||110 - 380||4.0||1.0||400||2, 4|
Several molecules of high astrophysical importance have transitions in the frequency band 66 - 80 GHz, i.e. between the atmospheric absorption band and the low frequency edge of the nominal 3mm tuning range (see Tab.1). Tests have shown that both 3mm receivers, A100 and B100 have good performance (good USB rejection and system temperature) in the range 77 - 80 GHz. The receivers become increasingly DSB 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 IRAM web site (at ../IRAMFR/PV/veleta.htm). The report includes a set of reference spectra.
Following the considerable demand for this frequency range in the last 2 semesters, the LO hardware has been simplified. As a result, observations in the 72 - 80 GHz range do not require any special arrangements, except that the A230 (B230) receiver is unusable when the A100 (B100) receiver is used below 80 GHz.
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.
An upgrade of the IF polarimeter  is now available, 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.
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 (H. Wiesemeyer, wiesemeyiram.fr). A short guide (at ../IRAMFR/PV/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 ).
The bolometer arrays, MAMBO-1 (37 pixels) and MAMBO-2 (117 pixels), are provided by the Max-Planck-Institut für Radioastronomie. They consist of concentric hexagonal rings of horns centered on the central horn. Spacing between horns is . Each pixel has a HPBW of 11. We expect that MAMBO-2 will be normally used, but MAMBO-1 is kept as a backup.
The effective sensitivity of MAMBO-1 for onoff and mapping observations is
For MAMBO-2 effective sensitivities of
46 mJys (ON/OFF mode) and
52 mJys (mapping mode)
were measured. The rms, in mJy, of a MAMBO-2 map is typically
The bolometer arrays are mostly used in two basic observing modes, ON/OFF and mapping. Previous experience with MAMBO-2 shows that the ON/OFF reaches typically an rms noise of 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 as 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. A typical single map3with MAMBO-2 covering a fully and homogeneously sampled area of (scanning speed: per sec, raster step: ) 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 ( ) must be larger than the map size (add the wobbler throw and the array size (), 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. If maps with an rms mJy are proposed, the proposers should contact R. Zylka (zylkairam.fr).
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, 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 (zylkairam.fr). The older software packages (NIC  and MOPSI) are still available, but will not be updated.
Bolometer proposals will be pooled together like in previous semesters along with suitable heterodyne proposals as long as the respective PIs agree. 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 (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.
Table 2 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. .
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 (see  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. 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. Peñalver has nearly completely removed the astigmatism.
With the systematic use of inclinometers the telescope pointing became much more stable. Pointing sessions are now scheduled at larger intervals. The fitted pointing parameters typically yield an absolute rms pointing accuracy of better than . Receivers are closely aligned (within ). 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 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 ().
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).
The following four spectral line backends are available which can be individually connected to any single pixel receiver and, if indicated, also to HERA.
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.
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.
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 Newsletter contribution  and in a user guide, but are best visualised on a demonstration program which can be downloaded from our web page at URL ../IRAMFR/PV/veleta.htm. Connected to a set of 4 single pixel receivers VESPA typically provides up to 12000 spectral channels (on average 3000 per receiver). Up to 18000 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 18000 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.
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 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 ../IRAMFR/TA/backend/veleta/wilma/index.htm.
Note that WILMA cannot presently be connected to any of the single pixel receivers.