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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.
Next: VLA Standard Bands.
Up: Old VLA
Previous: VLA-Only Project Example
Contents
Craig Walker
2014-04-14