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lbaops:lbacalibrationnotes:antab

ANTAB files for LBA data

If you wish to apply measured Tsys corrections, you will need to create an ANTAB file from the various telescope log files. [link to example]

  • Hobart, Ceduna, Yarragadee and Katherine provide files in ANTAB format, with Tsys measurements in units of Jy. These should be placed in the ATNF FTP area for each experiment after the session. DPFU in the GAIN group of the ANTAB file should then be set to 1.0 for these telescopes.
  • A scaling factor needs to be applied to raw Tsys numbers from Parkes to convert to units of Jy. Parkes calibration information (from some sessions) is provided here on the wiki.
  • For the ATNF telescopes, Tsys and off-source flagging logs should be linked from the experiment wiki page on the ATNF observers wiki. (Note that ATCA Tsys for VLBI data is not currently available, since the CABB upgrade.) For other participating telescopes, ANTAB or Tsys, off-source flagging and other log files should be in the ATNF FTP area for the given experiment (linked from the observers wiki page). See the notes on LBA log files.
  • Other stations usually provide Tsys measurements in K. The DPFU, if not provided, should then be set to the nominal DPFU: Tsys(K)/Tsys(Jy) from the table of system parameters.
  • Gain curves may be provided for some stations (e.g. Hart, AuScope antennas). ATCA and Mopra gain curves can be approximated as flat (POLY=1) at all VLBI frequencies. Some other potentially useful gain curves of varying ages are provided in ANTAB format here. Below are two more recent gain curves for Hobart and Ceduna courtesy of S. Ellingsen (2008).

Note these are not in the correct format for ANTAB. They can be converted into a table of values for ANTAB:
Ceduna (at 6.7 GHz, should be OK for 8.4 GHz): 1/[3.8e-5*el^2 - 3.575e-3*el + 0.9165]
Hobart (8.4 GHz): 1/(1.1377-2.5673e-2*el+1.1744e-3*el^2-2.1322e-5*el^3)+1.3452e-7*el^4)

  • When creating the ANTAB file, be sure to edit the antenna names if required, to ensure that the names match with those in the FITS file/AIPS ANtenna table (usually this will be the two-letter station code, especially for recently correlated data, but should be checked as other antenna names may be used). Also check that the INDEX keyword value assigns the columns to the correct IFs/polarizations.
  • As a sanity check, the amplitude gain in the final CL table should correspond approximately to the corrections from ACCOR multiplied by the square root of nominal SEFD for each telescope, assuming telescope performance is as expected. (This is not true for data correlated pre-2010, in which case the data have been scaled by the nominal SEFD, and the gain amplitudes should be not too far from 1 if the telescope performed at its nominal sensitivity).
lbaops/lbacalibrationnotes/antab.txt · Last modified: 2015/12/18 16:38 (external edit)