VLA/VLBA Polarization Previous News

Steve Myers & Greg Taylor

NRAO, Socorro

Last update: 26 May 2005

  Previous News:
  • The K-band subreflector rotations have been reoptimized as of Mon 13 Jan 2003, so current posted gain curves are invalid. See note on the Gain Curve Page.

  • A list of VLA memoranda dealing with polarization issues is available here. This is somewhat out of date and unfortunately most memoranda are not available on the web, only in hardcopy form at NRAO libraries. (2002-9-18)

  • Models are now available for 3C138 (0521+166) and 3C147 (0542+498) at U, K and Q bands in the Image Archive in addition to those for 3C48 and 3C286. These are FITS images with clean-components tables on the 1999.2 flux scale, courtesy Claire Chandler. See Claire's Page for details. (2002-6-27)

  • A record of the VLA d-terms culled from the PCAL output from the calibration runs is now available here. Beware, as changes due to antenna moves, reference antenna changes, and receiver changes have not been taken into account. Note also that these have been computed before the R-L phase differences were calibrated using 3C48/3C286. Still, these may be of interest to check if your solutions are reasonable. Upon request, I can provide the data files from a given run so that the AN table can be copied to apply these d-terms to your data. (2002-3-20)

  • The latest versions of the RUNFILEs that load the automatic AIPS procedures are available below.(2002-3-11)

  • Updated Q, K and U band gain curves are now available from the VLA Gain Curve Archive Page. Note that the new November 2001 gain curves supersede the curves from October 2000 and should be used especially for K and Q band data taken June 2001 onwards. (2002-2-8)

  • Data from 2002 is now available, and should have the correct gain and opacity corrections. Note that now all frequency bands are on the 1999.2 flux scale. The session reports are now available for 2002 along with the previous 2000 and 2001 reports. (2002-1-21)

  • Tables and Plots now available split by year. A one-month overlap with adjacent years is built into the tables and plots. (2002-1-14)

  • WARNING: The K and Q data starting from 21-SEP-2001 will have had gain and opacity corrections applied twice. I don't see anything visible in the plots, but I will be redoing these.

    NOTE - In the AIPS versions 31DEC01 and later, FILLM will by default apply gain curves and approximate opacity corrections, and thus you should not use manual gain curve corrections unless you defeat these (check BPARMS). You can check your CL 1 table to see if you have this problem also. If so, you can delete CL 1 and remake it with INDXR to start over with unity gains.

    If you want to use TIP curve derived opacities in CLCOR, set BPARM(1)=-1 to turn off the automatic application of WX-based opacities when using the 31DEC01 or 31DEC02 AIPS. Because the WX opacities are not very accurate, and are time variable over the run, I do not recommend using these at this time if better TIP data is available. I will investigate this further.

    Note also that there seems to be a problem with the flux densities referenced to 0137+331 from 20001022 to 20010623 (see 2355+498 Kband) - I will try to chase this down. (2002-1-11)

  • Starting with the C-config 2001-07-02 calibration runs, we are using the new (1999.2) flux density scale and Claire Chandler's models for 3C48 and 3C286 at K and Q band (see below). You will note a jump in the flux scale, especially for sources indexed to 3C48, at this point in the archive. We will back-propagate this calibration as soon as we can. (2001-7-27)

  • On 8 June 2001 (1600 UT), optimization was carried out for the installed Q-Band systems taking into account proper subreflector rotation for the feed locations of the receivers. As a consequence of this, AN 2, 21 and 26 should look better at least at the nominal elevation of about 50 degrees. All other antennas, with the exceptions of AN 3, 4, 6, 8, 12, 13, 14, 16, 22, and 27 (which had already had this rotation trick applied) will see improvement at extreme elevations and flatter gain curves in general. Unfortunately, this means the previous gain curves for all but AN 3, 4, 6, 8, 12, 13, 14, 16, 22, and 27 will now be invalid to some extent. We will try to obtain new gain curves soon but until this time you may find that the old gain curves will no longer work well. (2001-6-14)

  • Claire Chandler is producing better K and Q band models for primary calibrators 3C48 (J0137+331) and 3C286 (1331+305) in A-configuration and A+B configurations. You can download these FITS models from her calibration web page. Available models:

    K BandQ Band
    3C48_AK.ICL 3C48_ABQ_NA.ICL
    3C286_AK.ICL 3C286_AQ.ICL

    Note that these models are calibrated to the new flux scale. (updated 2001-4-30)

  • VLA images and clean models for 3C48 and 3C286 from this past A configuration are available here. The were calibrated using the old flux density scale - the scale was updated in Dec 2000 and eventually we will update the database to use this. (2001-2-16)

  • VLBA Scientific Memo 26 detailing this program is now available. (2000-10-4)

  • VLBA images of selected calibrators are now available - see below (2000-9-22)

  • Plots of individual source fluxes and polarization now available from tables (2000-9-11)

  • Of course, there is the main VLA Calibration Manual and list of calibrators

  • If you have scheduled tipping scans in order to determine atmospheric optical depths, you can find the results on Bryan Butler's Tip Scan Archive page.

  • The results of these calibration runs, in addition to providing information on source polarizations and fluxes, serves to check the performance of the VLA antennas. After each calibration run, a report is generated and sent to VLA antenna and correlator personnel. There is an archive of performance and reduction reports by session (since March 2000) available for browsing.

Modified on Thursday, 02-Sep-2010 17:00:35 MDT