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Parameters Specific to the VLA

The VLA capabilities in SCHED are for the old VLA system that has been shut down. Stay tuned for instructions related to running the EVLA (VLA).

This section gives a brief description of each of the parameters available to SCHED that are specifically for VLA observations or are especially useful for VLA observations. More general purpose SCHED parameters that are also required for other stations are not mentioned. For details on the parameters, consult the detailed descriptions of each parameter. The first list is of parameters in the main schedule input. The second is of setup parameters.

• VLATYPE: Specify the type of observations. Should be provided for non-VLBI observations. Valid options are 'VLBI', 'CONTINUUM' or 'LINE'.

• VLATSYS and VLANTSYS These turn on and off the Tsys corrections made to the correlated VLA data. This used to be required in order to obtain calibration data for the VLBI observations. That is no longer true so most observations can be made with the Tsys corrections turned on which is now the default.

• VLAPEAK controls reference pointing on the VLA. It is a good idea to do reference pointing when observing at 7 mm. See the section on Reference Pointing to see how to get SCHED to insert reference pointing scans automatically.

• VLAUSERN: This gives the VLA user number. The default of 600 is reasonable for VLBI but the actual user number should be provided for other types of projects.

• VLAMODE: Specify the VLA mode. Common options for VLBI are ' ', VA, VX, or VS. See VLA documentation on the many others that are available for non-VLBI observations.

• LST: Schedule is assumed to be in LST. LST specified without a value assumes the VLA. A station name can be given as the argument, in which case the LST is for that station. When LST is specified, the DAY must be the modified local sidereal day number as found on VLA monthly schedules.

• DAY: Must be the modified local sidereal day number as found on VLA monthly schedules if LST is specified. In such cases, YEAR and MONTH are ignored.

• IATUTC: Difference between IAT and UTC, which is currently about 30 seconds. This is only used for setting the zero offset epoch for the ``//PM'' (proper motion) card.

• SETUP: Specifies the setup file from which information for the ``//LO'' and ``//FI'' cards are taken.

• FREQ: and DOPPLER Warning -- these parameters cannot be used for non-VLBI observations at the VLA since they are only used to adjust the baseband converter frequencies.

• RECord: and NORECord These parameters find one of their main uses in observations that use the VLA, especially the phased array. It is often useful, for both phasing scans and for scans inserted just for calibration of the VLA, to be able to turn the VLBI recorders off. RECord and NORECord can be used to specify which scans should be recorded on the VLBI drives and which should not be.

• VLAPSRC: Phasing source to use before a VX mode scan. This is a convenient way to insert VLA phasing scans without having to explicitly include extra scans in a VLBI schedule.

• VLARFANT: Reference antenna to use for single dish data source or as phasing reference for phased array. The default should be good, and, if not, operations is likely to need a last minute change, so it is unlikely that users should use this parameter.

• VLAINTEG: This parameter gives the correlator integration time. It would normally be used to give a value less than 10 seconds to encourage faster phasing.

The parameters in the setup file that apply only to the VLA are below. They are used to set the band and bandwidths of the VLA and for setting up the ``//FI'' and ``//LO'' cards.

The values for all of these parameters, except FLUKESET, VLAIF, and VLAROT,, which are not normally needed, can be determined by SCHED from the frequency catalog. Therefore most projects do not require VLA specific parameters in the setup files.

The setup file parameters are:

• FEFILTER: The front end filters are normally 50 MHz wide. If there is strong RFI near the observing frequency, as is common at L and P bands, it may be desirable to use the 25 MHz or 12.5 MHz front end filters. This parameter is used to request the filters to use. It goes on the ``//LO'' card.

• FLUKESET: Which flukeset (1 or 2) to be used. Unfortunately there seems to be no good way to predict this reliably. Usually Flukeset 1 will be used for phased array and normal VLA observations while Flukeset 2 will be used for single antenna VLBI, but this is not always true. The VLA operators should be alerted that Flukeset specified on the ``//FI'' card might have to be changed. If it is not specified, or is set to 0, a blank will be given and the VLA operators will set it.

• VLABAND: Specify the frequency band. Must be one of the defaults without the //LO and //FI cards. Some valid options are VP, VL, VC, VX, VK, PP, LL, CC, XX, UU, KK, HH, or 18. For complete information on the standard bands, see the following section.

• VLABW: Specify the back end bandwidth for each of the 4 VLA IFs as a 4 digit number in quotes (SCHED  treats it as a character string), with one digit for each IF. The default is '0000' for 50 MHz in each IF. The consequent back end bandwidth is 50/(2**n) MHz, where n is the digit specified.

• FLUKEA: A Fluke synthesizer frequency. It is usually near 100 MHz. See the document ``VLBI at the VLA'' for details on what it should be. See Section 2.5 for more information on the frequency settings.

  FLUKEB: B Fluke synthesizer frequency. Actually this is the value for the ``//FI'' card which is twice the actual synthesizer setting. To get the same frequency on the AC and BD IFs, FLUKEB should be FLUKEA plus 100.0.

  VLAFEAB: 1st LO for the VLA observations for the AB (RCP) IFs. For standard VLBI projects, the value should be -3.2 for L band, 0 for C band, and 17.5 for K band. Again see VLA documentation for details of other alternatives.

  VLAFECD: Same as VLAFEAB but for the VLA's C and D (LCP) IFs.

  VLASYNA: 2nd LO for the VLA A and C IFs. On the ``//LO card'' this number is rounded to the nearest MHz, but it should be given here exactly. It is usually near 3900 MHz. It must be a value of N * 50 +- 10.1 MHz.

• VLASYNB: Same as VLASYNA but for the VLA B and D IFs.