Diff for "TelescopeSystemStatus"

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• This page provides information on the current status of the 30m telescope. It is intended for visiting astromers at the telescope and for astronomers preparing 30m observations. The IRAM staff tries to keep this page up to date as much as possible, however, some information may still be outdated. Please contact the Astronomer of Duty (AoD) or Operator in case of doubt. For an overview of the entire system and its performance, see the [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemSummary Telescope System Summary]. (CK, 30.8.08)

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System - General

• Observations less than 5 degree from the Sun are not yet supported. There is no specific alarm, but integrations don't start and tracking errors remain high.

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Antenna and wobbling secondary

• Observations with high wind speeds are degraded in a similar way. At velocities of more than about 15m/s tracking errors become larger than usual. In addition, the wind load may lead to deformations of the primary dish, depending on direction and orientation of the telescope (Morris et al. 2006). In this case, consider changing to a different source at a different antenna position. If the wind becomes too strong and puts the antenna in danger, the operator may have to decide to stop the observations and put the antenna in the safe stow position. (CK&JP 1.9.08)

• Observations at high elevations are degraded for several reasons. Antenna tracking errors, i.e. deviations between the commanded and actual position of the telescope, of more than 1 arcsecond are known to occur at elevations of more than about 84 degrees. In addition, residual gravitational deformations of the primary lead to a degradation of the point source sensitivity as reflected by the gain elevation curve (see e.g. Annual Report 2007 or the 30m manual). The magnitude of the latter effect increases with observing frequency. In this case, consider changing to a different source at lower elevations or contact the AoD for advice. (CK, 1.9.08)

• Bolometer observations with "rotated" wobbler are now possible. The permitted rotation range is +- 65 deg., in a fixed rotation, without tracking on the sky (the limitation for the tracking comes from the observing program). After finishing with rotated Wobbler, make sure that the operator puts the rotation back to exactly 0 degrees. (JP&CK 1.9.08)

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Frontends

SIS Receivers A, B, C, D

• A230 shows instabilities near 220 and 230GHz leading to degraded baselines. This is under investigation. (ck, 31.8.08)

• Image/Signal gain-ratio calibration using the continuum backends(!) is supported by NCS, processing in MIRA. It is highly recommended to use this feature!

• A standard table of T_cold calibration temperatures for A, B, C, D receivers is implemented in the NCS. This built-in table covers most frequencies. Outside this range, T_cold has to be set manually, ask the RX engineers or operators! [http://gra-lx1/mainWiki/ReceiverGroupColdLoadPlotsCurrent Tables and plots (internal link)] (2007-10-11 dj)

• Receiver C150 shows low continuum signal at the higher frequencies (>168 GHz). It has to be fully checked. Use D150 instead. (2005-11-16)

• In the receiver cabin, Martin-Puplett interferometers MPI are used to seperate frequencies to be send to two different receivers. An overview of the receiver cabin optics is given [http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver6.html here]. The MPIs have high losses at certain frequency ratios, especially at a ratio of 3. Simultaneous observations of e.g. HCN(1-0) and HCN(3-2) or HCO+ are therefore difficult and may lead to increased receiver noise temperatures, depending on how the MPI is optimized.

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HERA

HERA is a HEterodyne REceiver Array, a 3x3 dual polarisation array in the 1.2mm band. For details on HERA see the [http://www.iram.es/IRAMES/telescope/telescopeSummary/telescope_summary.html Telescope Summary page] or the [http://www.iram.es/IRAMES/mainWiki/HeraWebPage HERA page].

• SSB (Single side band) tuning tables for standard frequencies.

• Only few frequencies can be tuned automatically. Observers should send observing frequencies to the IRAM Granada receiver group at least three weeks in advance.

• Sideband rejections not determined (2004-12-01 AW). Use standard value of 0.1!

• For HERA calibration, measured values of the load temperatures are automatically used!

• Watch the computer control of the derotator closely (2002-12-22). Make sure the derotator tracking is stopped after observations, i.e., set to zero degrees in "frame".

• The automatic tuning of both HERA1 and 2 can be improved by manually changing the mixer current according to DJ; HERA Pool managers should be aware of this, and operators will receive training (2007-09-19 RM)

• HERA 2 is more noisy than HERA 1, limiting HERA2's useful frequency range to below about 242 GHz (2006-09-27 HU according to info from SN)

• Tests have shown that the pixels of HERA-2 (second polarisation) have relatively strong variations of noise over the IF band (LSB Tuning). While the consequences are not too dramatic for wide band operation (WILMA) unfortunately the narrow band mode as used mostly with VESPA picks up the end of the IF band with the highest noise. The problem will be further investigated and eventual improvements indicated asap.

• The control software does not yet support connecting HERA2 to the 4MHz backend (2008-08-29 wb). Note that paKo does not issue any warning. (ck)

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Bolometers

Details about the bolometers are given on the [http://www.iram.es/IRAMES/telescope/telescopeSummary/telescope_summary.html Telescope Summary page] and on a dedicated [http://www.iram.es/IRAMES/mainWiki/MamboWebPage MAMBO page.]

• MAMBO1 is OFFLINE
• MAMBO2 was re-installed and commissioned the week 13.11.2007/20.11.2007 (AS)
• MAMBO2 is on standby (ck 30.8.08)

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Backends

• VESPA spectra occasionally show spikes at band edges. Check with the AoD to run vespamon.py to check where the problem stems from. The local expert of VESPA is Gabriel Paubert. (30.8.08 ck)

• 4 MHz Filterbanks cannot be used with HERA2 (28-8-08 wb, ck)

• ABBA1 is active as ABBA2 is currently commissioned at the MPIfR. It shall be reinstalled in September 08. (ck)

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Computer/Software

• The New Control System (NCS) supports source coordinates in Equatorial J2000.0 system. More coordinate systems, i.e. B1950, Galactic Coordinates, etc., will soon be available. You may want to try NASA's [http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/convcoord/convcoord.pl HEASARC tool].

• Midnight bug: Online data processing has problems with scans extending over midnight. Please check data and report problems to the AoD and Albrecht Sievers. It is safer to avoid long scans extending over midnight. (updated by ck, 3.9.08)

• It is recommended to run the observations, i.e. to run Pako, on mrt-lx1. Pako does not run under the default gildas version on mrt-lx3, mrt-lx2. Use gag_aug06 before starting pako (2008-01-15 AS). BR Note: the instructions to start pako explicitly say to run it on mrt-lx1. The trick suggested by AS for mrt-lx2, mrt-lx3 may work, but it is not guaranteed. (update by ck)

• Data processing using MIRA or CLASS on mrt-lx3 occasionally slows down the observing system on mrt-lx1 as both system currently access the same disk, /vis, which is at present connected to mrt-lx3. This may mean that the work on mrt-lx3 has to be stopped as observations have priority. Please contact the AoD in case of such problems; for work with CLASS/GREG is helps to copy the 30m file over onto the local disk of mrt-lx2 and to continue working there. For MIRA processing of raw data, this would not help. We are working on a better solution. (2008-08-29 wb, ck)

• Automatic calibration and processing of heterodyne data using the MIRA software is in operation for all observing modes. MIRA can also be used manually and offline.

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Pointing

Heterodyne Pointing Model and Focus

The Pointing Model is maintained with respect to the 3mm receiver B100. The misalignment and focus error (D-focus) of the other receivers with respect to B100 is the following:

  Rx       misal.(")       date            D_focus(mm)       date
 A100     0.16 ±0.06     27-Feb-07,        +0.09 ±0.03     13-Mar-07
 A230     1.34 ±0.18     27-Feb-07,        +0.43 ±0.02     13-Mar-07
 B100     0.00                              0.00
 B230     1.74 ±0.16     27-Feb-07,        +0.40 ±0.10     17-Apr-07
 C150     1.26 ±0.24      5-Feb-07,        +0.64 ±0.13     17-Apr-07
 C270     0.78 ±0.18      5-Feb-07,        +0.36 ±0.15     17-Apr-07
 D150     1.03 ±0.13     12-Mar-07,        +0.26 ±0.02     12-Mar-07
 D270     1.40 ±0.19     12-Mar-07,        +0.18 ±0.05     12-Mar-07

• Pointing on spectral line sources like SiO masers is not yet supported by the data processing.

• heterodyne pointing model: last update: 2008-06-25, 29 points, previous rms = 2.58", new rms = 1.97"

Bolometer Pointing model

• bolometer pointing model: last update: 2007-12-19, 46 points, previous rms = 2.33", new rms = 1.75"

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Pointing with SIS receivers

• Continuum instability ("ripple") can occur with all receivers, making pointing and focusing difficult.
• In general some receivers are better than others in this respect as summarized here:
  • A100 generally OK for pointing. (2003-11-12)

  • B100 OK, is best for pointing. B100 is the standard reference for the heterodyne pointing model

  • C150 often bad for pointing, ripple. (2002-07-16)

  • D150 generally good performance for pointing.(2002-07-16)

  • A230 often unstable, bad for pointing and flux monitoring. (2003-11-12)

  • B230 OK

  • C270 can be unstable and difficult for pointing. (2007-04-30)

  • D270 can be unstable and difficult for pointing. (2002-07-16)

  • With HERA pointing may be difficult using beam switch mode - total power mode may give better results but requires excellent weather

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Remote Observing

[https://mrt-lx1.iram.es/mainWiki/RemoteObserving Remote observing (internal link)] via VNC is available from Granada, Grenoble, Madrid, and Bonn.

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Updates/History/Legend

To see the changes between the actual and the last version, please see Show Changes in the Wiki Interface. If you want to see the Revision History of this page, please see Get Info in the Wiki Interface.

: OKBR : WarningBR : ErrorBR

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(./) : OK
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{X} : Error

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This is page http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus, moderated by Carsten Kramer